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CHECKPOINT-INHIBITOR TOXICITY

Rheumatologic immune-related adverse events

Mostly arthralgia and myalgia, which are common and rarely dangerous. The exception carried here is myositis — around 1% on anti-PD-(L)1, and the member of the myositis/myocarditis/myasthenia triad most likely to present first.

A patient with weakness and a raised CK is a triad work-up, not a muscle problem: SITC monitors every possible myositis for myocarditis and myasthenia gravis, and myocardial involvement changes the ICI decision from hold to permanent discontinuation. Educational reference, not medical advice.

Anchored on the ASCO, EULAR and SITC chapters for this organ. Every source is named beside the position it supports, and labeled with what kind of source it is.

At a glance

ICI-associated myositis

Also called: inflammatory myopathy · ICI myositis · immune-related myositis · checkpoint inhibitor myopathy

Around 1% on anti-PD-(L)1, and the member of the myositis/myocarditis/myasthenia triad most likely to present first — 9% of cases carry myocarditis and 9% myasthenia gravis. CK cuts both ways: some patients are asymptomatic with a raised CK, others symptomatic with a normal one, so neither result closes the question.

Part of a syndrome that spans more than this organ — see Spans more than this organ below.

RareCriticalonset: any time on therapy

Reported frequency

  • 1% — Myositis in patients treated with anti-PD-(L)1 ICIs

    of Not stated in the chapter · SITC's chapter statement, given without a cohort or denominator. Carried because it is the only frequency figure any source held here reports for this entity, and its denominator field says what is missing

    guideline · 34172516

Severity and class

  • 1% anti-PD-(L)1 vs <1% anti-CTLA-4 — Myositis frequency by ICI class

    of Not stated — SITC gives the two class figures without numerators or cohort sizes · SITC's chapter statement. The chapter adds that little systematic data exist for other ICIs, so this comparison covers two classes and not the field

    guideline · 34172516

Onset

No source cited here reports an onset window for ICI myositis. The neurological median of 29 days belongs to myasthenia gravis in a different study and is not carried across, even though the two co-occur. The bucket does not narrow a statement no source made.

Presentation

  • · Muscle weakness in the limbs, and myalgia
  • · Restricted eye movement
  • · Problems with speaking or swallowing
  • · Asymptomatic with an elevated CK — SITC names this as a presentation, so a raised CK on a routine panel is a finding, not noise
  • · Symptomatic with a NORMAL CK — the converse SITC also names, and the reason a normal CK does not exclude myositis

Differential

  • · Myasthenia gravis, which SITC separates electrodiagnostically and which carries 9% of myositis cases — fatigable weakness with ptosis and diplopia points there
  • · Myocarditis, present in 9% of myositis cases and the reason cardiac testing belongs in this work-up rather than in the follow-up
  • · Statin and other drug-induced myopathy
  • · Hypothyroidism, itself an ICI toxicity, and other metabolic causes of a raised CK
  • · Malignant infiltration, deconditioning and cachexia

Work-up

  • Rheumatology or neurology consultation · All patients

    SITC attaches it to POSSIBLE myositis, before the diagnosis is established, and again at grade 3.

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  • Creatine kinase · All patients

    The central test and the one most likely to mislead. SITC states both failure modes explicitly: asymptomatic patients with raised CK, and symptomatic patients with normal CK. Its trajectory also gates the 4-6 week escalation decision.

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  • Monitoring for signs of myocarditis · All patients

    SITC requires it in every possible myositis. This is the finding that converts the ICI decision from hold to permanent discontinuation, and myocarditis is the member of the triad with 50% reported fatality.

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  • Monitoring for signs of myasthenia gravis · All patients

    The third member of the triad, present in 9% of myositis cases; SITC evaluates all three together.

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  • Assessment of respiratory and diaphragmatic muscle involvement · All patients

    SITC names diaphragmatic or respiratory muscle involvement as a direct mechanism of death from myositis itself, separate from the myocarditis route.

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  • Assessment for dysphagia · All patients

    Difficulty swallowing is both a presenting symptom and, at grade 3, one of the three findings that triggers IV methylprednisolone with plasmapheresis or IVIG.

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Grade ladder

Grade 1
Continue the ICIOutpatient

Grade 1 — and the rung with a trap in it. ASCO's cross-organ default continues an ICPi at grade 1 and its exceptions are neurologic, hematologic and cardiac, not musculoskeletal, so on its face it applies here. SITC overrides it conditionally: grade 1 myositis presenting with an elevated CK AND muscle weakness should be managed as grade 2. A grade 1 myositis with both findings is therefore not a grade 1 decision.

Dose not carried

SITC offers oral corticosteroids at this level and states no dose, route, taper or duration for them — the chapter's only myositis dose is the grade 3 prednisone 1 mg/kg. The rung records that a steroid may be offered without a dose being carried, rather than importing the grade 3 figure downward.

  • · Analgesia with acetaminophen or NSAIDs if no contraindications are present
  • · Rheumatology or neurology consultation — SITC attaches it to possible myositis, not to a grade
  • · Monitor for myocarditis and myasthenia gravis from the first presentation

Escalate when: An elevated CK together with muscle weakness — SITC's explicit instruction is to manage that combination as grade 2, so it is the trigger rather than a reason to watch. Any cardiac or myasthenic sign escalates independently.

Grade 2
Hold the ICIOutpatient

Grade 2 — ASCO may suspend the ICPi for most grade 2 toxicities, with consideration of resuming when symptoms revert to grade 1 or lower. This rung also receives the grade 1 cases that carry both an elevated CK and muscle weakness.

Dose not carried

Same as grade 1: oral corticosteroids are offered without a stated dose. SITC's 1 mg/kg prednisone figure is written for grade 3 and is not pulled down to this rung.

  • · Analgesia with acetaminophen or NSAIDs if no contraindications are present
  • · Serial CK, since its trajectory gates the later escalation decision
  • · Continue monitoring for myocarditis and myasthenia gravis

Escalate when: Weakness severely limiting mobility, dysphagia, or any cardiac or respiratory involvement. A rising CK on treatment.

Grade 3
Hold — consider permanent discontinuationConsider admission

Grade 3 — the rung where SITC becomes specific. Refer to rheumatology or neurology, consider hospitalization for severe weakness, hold the ICI until myositis is grade ≤1 while OFF immune suppression, and permanently discontinue if there is any evidence of myocardial involvement. That last clause is the reason the cardiac assessment is part of the work-up rather than a later question.

Corticosteroid 1 mg/kg/day (oral)

Pulse: Methylprednisolone IV 1–2 mg/kg, or a higher-dose bolus — SITC scopes this to grade 3 myositis WITH muscle weakness severely limiting mobility, cardiac or respiratory involvement, or dysphagia — not to every grade 3. Plasmapheresis or IVIG may be considered alongside it.

Taper over 4–6 weeks or longer, starting once: Not stated for this entity. SITC gives the starting dose and no taper; the window shown is ASCO's cross-organ 'at least 4-6 weeks', a FLOOR in its own text, rendered open-ended rather than as a completion date. Do not confuse it with SITC's separate 4-6 week non-response window, which triggers escalation rather than reduction.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • Rituximab — Used in primary myositis; SITC does not recommend it here so much as note the experience.SITC advises caution given rituximab's long biological duration — the concern is the length of immunosuppression in a patient with active cancer, not an absolute bar.
  • Plasmapheresis or intravenous immunoglobulin (IVIG) — Grade 3 myositis with weakness severely limiting mobility, cardiac or respiratory involvement, or dysphagia — considered alongside the IV methylprednisolone, not after it fails.
  • Methotrexate, azathioprine, or mycophenolate mofetil — Symptoms and CK not improving, or worsening, after 4–6 weeks. This is a non-response window, not a taper window.
  • · Hospitalization may be considered for severe weakness
  • · Establish whether there is myocardial involvement — it converts the hold into permanent discontinuation
  • · The bar for resuming is grade ≤1 while OFF immune suppression, not grade ≤1 on steroids

Escalate when: Respiratory or diaphragmatic involvement, evidence of myocarditis, or no improvement in symptoms and CK by 4–6 weeks.

Grade 4
Discontinue permanentlyAdmit

Grade 4 — SITC's musculoskeletal chapter states no grade 4 myositis paragraph. ASCO's cross-organ rule supplies the action: permanent discontinuation of ICPis at grade 4, with an endocrine exception that does not apply here. The management shown is SITC's grade 3 regimen, and the rung says so rather than presenting it as a grade 4 recommendation.

Corticosteroid 1–2 mg/kg/day (intravenous)

Pulse: Methylprednisolone IV 1–2 mg/kg, or a higher-dose bolus — Carried up from SITC's grade 3 escalation criteria, all of which — severe weakness, cardiac or respiratory involvement, dysphagia — are satisfied at grade 4. No grade 4 dose is separately stated.

Taper over 4–6 weeks or longer, starting once: Not stated for this entity; the floor is ASCO's cross-organ minimum taper length.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • Plasmapheresis or intravenous immunoglobulin (IVIG) — Severe weakness, cardiac or respiratory involvement, or dysphagia.
  • Methotrexate, azathioprine, or mycophenolate mofetil — Symptoms and CK not improving, or worsening, after 4–6 weeks.
  • · Admission, with respiratory support available for diaphragmatic involvement
  • · Permanent discontinuation of the ICI
  • · Cardiac assessment maintained — myocarditis is the other route to death in this entity

Escalate when: Already the top rung. Management of established respiratory failure or fulminant overlap myocarditis is beyond what the chapter held here states.

Rechallenge

Individualize the decision

Unusually for these cards, this one's chapter describes a route back rather than a stop. SITC holds the ICI at grade 3 until myositis is grade ≤1 while OFF immune suppression — a resumption condition, stated as such — and permanently discontinues only where there is evidence of myocardial involvement. So the stance turns on the cardiac question rather than on the myositis grade, and 'individualized' encodes that fork rather than flattening it. Note what is NOT here: no source cited reports a recurrence rate on resumption, and the 5-year figure SITC quotes runs the other way — half of myositis cases were ongoing or had left sequelae at the end of the observation period.

  • · Myositis at grade ≤1 while off immune suppression — SITC's bar, and it is off suppression, not on it
  • · No evidence of myocardial involvement; any such evidence makes discontinuation permanent
  • · Rheumatology or neurology involvement in the decision

Deliberately not carried

  • Where sources differ — Empty although THREE chapters are now held for this entity - SITC's, EULAR's myositis section, and ASCO's Table 5 section 5.2. ASCO and SITC do point different ways at grade 1: ASCO continues the ICPi outright, while SITC's rule keys off a raised creatine kinase with weakness rather than stating a grade-1 ICI action of its own. That was reviewed and deliberately NOT recorded as a disagreement: a 'sources differ' box needs two sources addressing the SAME decision, and SITC takes no grade-1 position for ASCO to differ from. The interaction is described in the grade 1 definition on the ladder instead.
  • Reported frequency — The 1% figure is SITC's chapter statement and comes with no cohort, denominator or study. It is carried because it is the only frequency any source held here reports for this entity, with its denominator field saying plainly that none was given. No primary myositis cohort was resolved in this pass — the pharmacovigilance study cited elsewhere in the atlas breaks out the neurological phenotypes, not myositis.
  • Grade 3 or higher share — Null. No source cited here reports a grade ≥3 rate for myositis. The neurological sub-1% high-grade figure carried on the neuro cards is organ-scoped to the nervous system and is not extended here.
  • Mortality — Null. SITC describes two mechanisms of death — associated myocarditis, and direct diaphragmatic or respiratory involvement — and states no rate for either. The 50% figure in the chapter is not mortality: it is the share of cases ongoing or with sequelae at 5 years, a different measure, and it is carried in the citation's quote and the entry prose rather than in this field.
  • Onset — No onset window is stated for myositis in any source cited here. The bucket is 'any-time' and all three numeric fields are null. Myasthenia gravis's 29-day median comes from a different study of a different phenotype and is not borrowed, notwithstanding that the two co-occur in 9% of cases.
  • Corticosteroid dose, grades 1-2 — SITC offers oral corticosteroids at these levels and names no dose. The chapter's 1 mg/kg prednisone is written for grade 3, and pulling it down would present a grade 3 dose as a grade 1 recommendation. Both rungs read 'Dose not carried' and say a steroid may be offered without a dose being carried.
  • Corticosteroid taper — No taper window, start trigger or step cadence is stated for myositis. Grades 3-4 show ASCO's cross-organ 'at least 4-6 weeks' as an open-ended floor labeled as ASCO's, with the step size and interval empty together. The taper line warns against confusing it with SITC's separate 4-6 week NON-RESPONSE window, which triggers escalation to steroid-sparing agents — two 4-6 week intervals in one chapter pointing in opposite directions is a real misreading risk.
  • The grade 4 rung — SITC's chapter has no grade 4 myositis paragraph. The action comes from ASCO's cross-organ grade 4 rule and the management is SITC's grade 3 regimen carried up, on the basis that every one of SITC's grade 3 escalation criteria is satisfied at grade 4. The grade definition states this rather than presenting the rung as separately sourced.
  • Linked society recommendations — Left empty although ASCO and SITC are both in this atlas's guideline library: the recommendation stored against each of them there is scoped to ICI-related kidney injury and would put kidney dosing on a rheumatology card.

Sources

  • Brahmer JR, et al. (2021) Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immune checkpoint inhibitor-related adverse eventsCited for: Myositis frequency by ICI class, its association with myocarditis and myasthenia gravis at 9% each, the mechanisms of fatality, the symptom range including the asymptomatic-with-raised-CK and symptomatic-with-normal-CK presentations, the 5-year sequelae figure, and the whole graded ladder — the rheumatology or neurology referral, the rule that grade 1 with raised CK and weakness is managed as grade 2, the grade 3 prednisone dose, the IV methylprednisolone and plasmapheresis or IVIG escalation, the hold-until-grade-1 rule with permanent discontinuation on myocardial involvement, the 4-6 week non-response trigger for steroid-sparing agents, and the rituximab caution.Supporting text: the full text
  • Kostine M, et al. (2021) EULAR points to consider for the diagnosis and management of rheumatic immune-related adverse events due to cancer immunotherapy with checkpoint inhibitorsCited for: That ICI myositis sits in the potentially-fatal spectrum through its association with myocarditis and myasthenia gravis, the excess mortality against idiopathic inflammatory myositis, the CK behavior in both directions, and the directive that cardiac evaluation be systematic in any suspected case.Supporting text: the full text
  • Schneider BJ, et al. (2021) Management of Immune-Related Adverse Events in Patients Treated With Immune Checkpoint Inhibitor Therapy: ASCO Guideline UpdateCited for: ASCO's Table 5 section 5.2 myositis chapter, and only that entity: that ASCO continues the ICPi at grade 1 outright, its grade-2 hold with prednisone 0.5-1 mg/kg where creatine kinase is raised, and its grade 3-4 row — written as one cell — with permanent discontinuation considered, higher-dose corticosteroid and the escalation options.Supporting text: the full text
  • Johnson DB, et al. (2019) Neurologic toxicity associated with immune checkpoint inhibitors: a pharmacovigilance study.Cited for: That myasthenia gravis was distinguished from the other neurological phenotypes by frequent CONCURRENT myocarditis and myositis, alongside its early onset and roughly 20% fatality — the pharmacovigilance evidence that this triad co-occurs rather than being three independent toxicities that happen to share symptoms.Supporting text: the PubMed abstract (checkable at the link above)

ICI-associated inflammatory arthritis

Also called: ICI arthritis · rheumatoid-like arthritis · psoriatic-like arthritis · reactive arthritis · synovitis

The rheumatological irAE most likely to outlast the drug: SITC's own second-line paragraph is written for arthritis that requires long-term treatment. Presentations are heterogeneous — rheumatoid-like, psoriatic-like, occasionally reactive — and most patients are seronegative, so a negative rheumatoid factor and anti-CCP argue against nothing. The dose here is ABSOLUTE, not weight-based: 10-20 mg/day of prednisone equivalents at grade 2, 40-60 mg/day at grade 3 or above.

UncommonSeriousonset: any time on therapy

Reported frequency

  • 1%-7% — Clinical-trial participants developing inflammatory arthritis

    of Clinical trial participants across the trials in the systematic review SITC cites · Reported by SITC from a systematic review of ICI-related inflammatory arthritis. The range is between studies, not a confidence interval, and SITC states no pooled point estimate

    guideline · 34172516

Onset

No onset figure is stated for inflammatory arthritis in the chapter held here. SITC gives a median onset for polymyalgia rheumatica (12 weeks) and for sicca (70 days) in the same chapter and none for arthritis, so nothing is carried across from its neighbors and the bucket is deliberately unnarrowed.

Presentation

  • · Joint pain with stiffness and swelling, heterogeneous in pattern — rheumatoid-like, psoriatic-like, and rarely a reactive arthritis
  • · Synovitis, tenosynovitis and/or enthesitis on examination — the findings that separate arthritis from arthralgia
  • · Impaired ability to perform activities of daily living, which is how this one costs a patient something
  • · MOSTLY SERONEGATIVE for rheumatoid factor and anti-CCP, though seropositive cases are reported — so a negative serology does not exclude the diagnosis

Differential

  • · Arthralgia without inflammation, which SITC treats as a separate and much commoner phenomenon and explicitly attributes in part to the cancer, to chemotherapy and to radiation rather than to the ICI
  • · Polymyalgia rheumatica — pain and stiffness centered on the shoulders and hips, evaluated with ESR and CRP rather than a joint count, and carried as its own card
  • · Myositis, where weakness and a raised CK rather than joint swelling are the finding, and which pulls the myocarditis and myasthenia work-up in with it
  • · Septic or crystal arthritis in a single hot joint
  • · A flare of pre-existing rheumatoid or psoriatic arthritis, which the ICI can unmask rather than cause
  • · Bone metastases and other malignant causes of regional joint pain

Work-up

  • ESR and CRP · All patients

    SITC's initial evaluation for possible inflammatory arthritis.

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  • Rheumatoid factor, anti-CCP and ANA · All patients

    Ordered by SITC, with the caveat SITC itself states: most patients are seronegative, so these characterize the phenotype rather than confirm or exclude it.

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  • Joint count · All patients

    The clinical measure SITC names, and what makes response to treatment assessable.

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  • Radiological investigation of the affected joints (X-ray, MRI or ultrasound) · If atypical

    Where appropriate, in consultation with a rheumatologist — SITC's own qualification.

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  • Rheumatology referral · Grade 2+

    SITC refers grade ≥2 OR persistent rheumatological irAEs to a rheumatologist, for choice and interpretation of testing as well as management. Persistence is a trigger in its own right, independent of grade.

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Grade ladder

Grade 1
Continue the ICIOutpatient

Grade 1 — SITC's dosing sentence starts at grade 2, and ASCO's continue-with-close-monitoring default at grade 1 excepts some neurologic, hematologic and cardiac toxicities but not musculoskeletal ones. So the drug continues and no systemic corticosteroid is carried at this rung.

No corticosteroid at this grade

SITC states its corticosteroid dose for grade 2 symptoms and above; it gives none for grade 1 arthritis. ASCO's cross-organ default at grade 1 is to continue the ICI with close monitoring. Neither is silence about grade 1 — both address it, and neither prescribes a systemic steroid.

  • · Close monitoring, which is ASCO's grade 1 instruction rather than an absence of one
  • · Refer if the arthritis PERSISTS — SITC's referral trigger is grade ≥2 or persistence, and persistence can be reached at grade 1
  • · Examine for synovitis, tenosynovitis and enthesitis; their presence is what moves this off the arthralgia reading

Escalate when: Joint swelling, loss of function in activities of daily living, or symptoms that persist rather than settle.

Grade 2
Hold the ICIOutpatient

Grade 2 — the rung SITC's dosing sentence is written for: corticosteroid dosing may START at 10-20 mg/day of prednisone equivalents. ASCO may suspend the ICI for most grade 2 toxicities, with consideration of resuming when symptoms revert to grade ≤1.

Corticosteroid 10–20 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks or longer, starting once: Not stated for arthritis. SITC gives the dose and no taper — unlike its sicca paragraph, which does give one — so the window shown is ASCO's cross-organ 'at least 4-6 weeks', a FLOOR in its own text, rendered open-ended.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • TNF-α inhibitors (e.g. infliximab), methotrexate, leflunomide, hydroxychloroquine, sulfasalazine, or IL-6 receptor inhibitors (e.g. tocilizumab) — Arthritis that requires LONG-TERM treatment or does not respond to corticosteroids — SITC's trigger is duration as well as failure.SITC states that the choice depends on severity, comorbidities and anticipated time to efficacy and should be managed by a rheumatologist; no ranking among these agents is given here, and none is invented.
  • · Rheumatology referral for choice and interpretation of testing as well as management
  • · Joint count and inflammatory markers at baseline, so response is measurable rather than impressionistic
  • · Steroid-sparing planning early if the arthritis looks like it will need long-term treatment

Escalate when: Grade 3 symptoms, no response to the starting dose, or a course that is clearly going to need long-term treatment.

Grade 3
Hold — consider permanent discontinuationOutpatient

Grade 3 — SITC's higher band: 40-60 mg/day of prednisone equivalents may be required for grade ≥3 symptoms. ASCO suspends the ICI and starts high-dose corticosteroids at grade 3, which is the same instruction from the other direction.

Corticosteroid 40–60 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks or longer, starting once: Not stated for arthritis; the floor is ASCO's cross-organ minimum taper length.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • TNF-α inhibitors (e.g. infliximab), methotrexate, leflunomide, hydroxychloroquine, sulfasalazine, or IL-6 receptor inhibitors (e.g. tocilizumab) — Long-term treatment requirement or corticosteroid non-response, managed by a rheumatologist.
  • · Rheumatology leads at this rung
  • · Function, not just inflammatory markers, is the endpoint — SITC frames this toxicity around activities of daily living

Escalate when: No response on the higher band, or progressive loss of function.

Grade 4
Discontinue permanentlyConsider admission

Grade 4 — SITC's dosing sentence covers grade ≥3 and does not separate grade 4, so the band is unchanged. ASCO's cross-organ rule is permanent discontinuation at grade 4.

Corticosteroid 40–60 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks or longer, starting once: Not stated for arthritis; the floor is ASCO's cross-organ minimum taper length.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • TNF-α inhibitors (e.g. infliximab), methotrexate, leflunomide, hydroxychloroquine, sulfasalazine, or IL-6 receptor inhibitors (e.g. tocilizumab) — Corticosteroid non-response or a long-term treatment requirement.
  • · Permanent discontinuation of the ICI, per ASCO's grade 4 rule
  • · Rheumatology-led long-term plan; this is the phenotype most likely to still need treatment after the drug has stopped

Escalate when: Already the top rung. SITC states no grade 4-specific regimen for arthritis beyond the band shown.

Rechallenge

Individualize the decision

No source cited here states a rechallenge position for ICI inflammatory arthritis. What SITC does say bears on it from an unusual direction: this is the toxicity it expects may need LONG-TERM treatment, so the practical question is often not whether the drug can be restarted but whether the arthritis has ever been off treatment. ASCO's rule is the cross-organ grade-4 one.

  • · Symptoms controlled at grade ≤1, which is the threshold ASCO names for resuming after a grade 2 suspension
  • · Clarity about whether control is being maintained BY ongoing immunosuppression — restarting an ICI into a patient on a TNF-α inhibitor is a different decision from restarting into one off treatment
  • · Rheumatology involvement in the decision, since SITC hands the medication choice to a rheumatologist

Deliberately not carried

  • Where sources differ — Empty. EULAR is a second anchor chapter for this organ, but only its MYOSITIS section was read for this atlas — its arthritis and PMR sections are unread, so there is no second position on this card's fields to compare. That is a limit of what has been read, not a finding that the societies agree.
  • Difference between ICI classes — Null. The chapter held here states no class comparison for inflammatory arthritis, and the neighboring cards' class skews belong to other phenotypes.
  • Reported frequency — Carries the arthritis figure only. SITC reports arthralgia at 1%-43% and myalgia at 2%-21% in the same chapter, and both are deliberately absent: SITC itself says attribution is confounded because arthralgia and myalgia also follow the cancer, chemotherapy and radiation, and they are a different entity from inflammatory arthritis. Putting a 43% ceiling on this card would read as the frequency of the arthritis it is about.
  • Grade 3 or higher share — Null. No source cited here reports a grade ≥3 rate for inflammatory arthritis — the 1%-7% is all-grade and is stored as incidence.
  • Mortality — Null. No fatality figure for inflammatory arthritis exists in any source cited here.
  • Onset — No onset is stated for arthritis in the chapter held here. No median is shown, both range bounds are empty and the onset window is 'any time' — the PMR and sicca medians in the same chapter belong to those entities and are not borrowed.
  • Corticosteroid taper — SITC gives arthritis a dose and no taper. Every dosed rung shows ASCO's cross-organ 'at least 4-6 weeks' as an open-ended floor, labeled as ASCO's on the taper line, with the step size and interval empty together. The sicca card in this same organ DOES carry SITC's own 4-6 week window, which is why this one says whose number it is showing.
  • Care setting — No care setting is stated for arthritis at any grade. Outpatient is the atlas's reading for a toxicity SITC manages with oral corticosteroids and a rheumatology referral; the grade 4 rung says consider admission on severity alone, not on a stated instruction.
  • Linked society recommendations — Left empty although ASCO and SITC are both in this atlas's guideline library: the recommendation stored against each of them there is scoped to ICI-related kidney injury and would put kidney dosing on a rheumatology card.

Sources

  • Brahmer JR, et al. (2021) Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immune checkpoint inhibitor-related adverse eventsCited for: The heterogeneous presentation of ICI inflammatory arthritis (rheumatoid-like, psoriatic-like, rarely reactive), the examination findings, the predominant seronegativity with reported exceptions, the 1%-7% figure from the systematic review SITC cites, the diagnostic evaluation, the rheumatology referral at grade ≥2 or persistent disease, the ABSOLUTE 10-20 mg/day and 40-60 mg/day prednisone-equivalent doses by grade, and the named steroid-sparing options for long-term or refractory disease.Supporting text: the full text
  • Schneider BJ, et al. (2021) Management of Immune-Related Adverse Events in Patients Treated With Immune Checkpoint Inhibitor Therapy: ASCO Guideline UpdateCited for: ASCO's Table 5 section 5.1 inflammatory-arthritis chapter, and only that entity: continue the ICPi at grade 1 with analgesia; at grade 2 hold temporarily with resumption on symptom control, prednisone 10-20 mg/d or equivalent, and escalation if no improvement after 4 weeks; and at grades 3-4 hold with resumption in consultation with rheumatology on recovery to grade 1 or less, prednisone 0.5-1 mg/kg, and a steroid-sparing agent where the response is inadequate.Supporting text: the full text

ICI-associated polymyalgia rheumatica (± giant-cell arteritis)

Also called: PMR · polymyalgia rheumatica · PMR/GCA · giant-cell arteritis · temporal arteritis

Pain and stiffness in the shoulders and hips at a median of 12 weeks, and SITC says the majority respond well to corticosteroids. The reason it is not a benign card is the rare companion: giant-cell arteritis, where visual symptoms must be assessed and SITC asks for a low threshold for temporal artery biopsy and URGENT corticosteroids because sight is what is at risk.

Frequency unclearSeriousonset: weeks 6–12

Onset

SITC states the median time to onset of PMR as 12 weeks. This is one of the few real medians in the atlas's rheumatology and neurology cards — it is the chapter's own figure for this entity, not a range borrowed from a group of phenotypes. No range around it is published there, so both bounds are null.

Presentation

  • · Joint pain and stiffness, PRIMARILY in the shoulders and hips
  • · Visual symptoms where giant-cell arteritis accompanies it — SITC's instruction is that these must be assessed, not that they usually occur
  • · Raised ESR and CRP, which are the whole of SITC's initial evaluation for this entity

Differential

  • · Inflammatory arthritis, which SITC evaluates differently — a joint count and a serological panel rather than ESR and CRP alone — and which is carried as its own card
  • · Myositis: proximal weakness with a raised CK rather than pain and stiffness with normal muscle strength, and a far more dangerous work-up path because of myocarditis
  • · Giant-cell arteritis as the accompanying rather than the alternative diagnosis — it is not ruled out by finding PMR, which is why the visual assessment is part of the PMR card
  • · Bone metastases and other malignant causes of shoulder and hip-girdle pain
  • · Hypothyroidism, itself an ICI toxicity, as a cause of proximal aching

Work-up

  • ESR and CRP · All patients

    SITC's entire stated initial evaluation for possible PMR.

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  • Assessment of visual symptoms · All patients

    SITC's instruction where GCA may accompany PMR. It belongs in the work-up rather than the follow-up because the loss it prevents is not recoverable.

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  • Temporal artery biopsy · If atypical

    SITC asks for a LOW THRESHOLD for it in suspected GCA, in consultation with a rheumatologist, because of the risk of visual loss. Urgent corticosteroids may be warranted alongside it.

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  • Rheumatology referral · Grade 2+

    SITC refers grade ≥2 or persistent rheumatological irAEs, PMR/GCA named among them.

    34172516

Grade ladder

Grade 1
Continue the ICIOutpatient

Grade 1 — SITC's dosing sentence begins at grade 2, and ASCO's continue-at-grade-1 default does not except musculoskeletal toxicity. The exception that overrides this rung is not a grade: suspected giant-cell arteritis warrants urgent corticosteroids whatever the PMR grade, because the risk is visual loss.

No corticosteroid at this grade

No corticosteroid dose is stated for grade 1 PMR — SITC's band starts at grade 2 — and ASCO continues the ICI with close monitoring at grade 1. This is a dose the chapter does not give at this grade, NOT a statement that steroids are unnecessary if giant-cell arteritis is suspected: SITC's urgent-corticosteroid instruction for suspected GCA carries no grade condition and is carried in the supportive measures.

  • · Assess visual symptoms — the assessment is not grade-conditioned
  • · Urgent corticosteroids and a low threshold for temporal artery biopsy if giant-cell arteritis is suspected, in consultation with a rheumatologist
  • · ESR and CRP as the baseline against which response is judged

Escalate when: Any visual symptom, jaw or tongue claudication, or scalp tenderness — the GCA features that change the urgency completely.

Grade 2
Hold the ICIOutpatient

Grade 2 — SITC's dosing sentence covers inflammatory arthritis AND PMR together: dosing may start at 10-20 mg/day of prednisone equivalents for grade 2 symptoms. The majority of PMR cases respond well to corticosteroids, which is SITC's own characterization of this entity.

Corticosteroid 10–20 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks or longer, starting once: Not stated for PMR. The window shown is ASCO's cross-organ 'at least 4-6 weeks', a FLOOR in its own text, rendered open-ended — PMR is a condition in which corticosteroid courses are commonly long, and nothing here licenses a completion date.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • Methotrexate, hydroxychloroquine, or tocilizumab — Corticosteroid-refractory PMR. SITC names these three as non-steroidal agents from which such patients may derive benefit — a shorter and different list from the one it gives for inflammatory arthritis.
  • · Rheumatology referral at grade ≥2 or persistence
  • · Continued visual-symptom assessment while on treatment
  • · ESR and CRP to track response, since the response SITC describes is usually prompt

Escalate when: Grade 3 symptoms, poor corticosteroid response — which is atypical here and worth re-examining the diagnosis over — or any GCA feature.

Grade 3
Hold the ICIOutpatient

Grade 3 - ASCO writes grades 3 and 4 as ONE row for this entity and does not discontinue: it holds the ICPi and permits resumption, in consultation with rheumatology, once the patient recovers to grade 2 or less, adding that cases of toxicity returning on rechallenge have been reported. Its dose here is prednisone 40 mg/d, which sits inside SITC's 40-60 mg/day band for grade >=3, the region in which giant-cell arteritis is also treated urgently.

Corticosteroid 40–60 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks or longer, starting once: Not stated for PMR; the floor is ASCO's cross-organ minimum taper length.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • Methotrexate, hydroxychloroquine, or tocilizumab — Corticosteroid-refractory PMR.
  • · Rheumatology leads; temporal artery biopsy at a low threshold if GCA is suspected
  • · Do not delay corticosteroids for the biopsy when visual loss is the risk — SITC pairs the urgent steroid with the biopsy rather than sequencing them

Escalate when: Visual symptoms, or failure to respond to the higher band.

Grade 4
Hold the ICIConsider admission

Grade 4 - neither chapter separates it. SITC's band covers grade >=3 as one, and ASCO writes grades 3-4 as a single row, holding rather than discontinuing and permitting resumption on recovery to grade 2 or less in consultation with rheumatology. ASCO's cross-organ grade-4 discontinuation rule is NOT applied here, because its own musculoskeletal chapter states otherwise for this entity.

Corticosteroid 40–60 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks or longer, starting once: Not stated for PMR; the floor is ASCO's cross-organ minimum taper length.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

Second line

  • Methotrexate, hydroxychloroquine, or tocilizumab — Corticosteroid-refractory PMR.
  • · Permanent discontinuation of the ICI, per ASCO's grade 4 rule
  • · Ophthalmology involvement where vision is affected — the eye card in this atlas is where ICI ocular toxicity is handled, and established visual loss is beyond what this chapter states

Escalate when: Already the top rung. ASCO adds prednisone 40 mg/d and, where there is no improvement or a prolonged need for higher doses, a steroid-sparing agent such as methotrexate or an IL-6 antagonist, with its own caution that IL-6 inhibition can cause intestinal perforation. No GCA-specific regimen beyond urgent corticosteroids is stated in either chapter.

Rechallenge

Individualize the decision

ASCO states one, and it is a route back rather than a stop: at grades 3-4 — which it writes as a single row — 'Hold ICPi and may resume, in consultation with rheumatology, if recover to ≤ G2', with the explicit caution that cases of toxicity returning upon rechallenge have been reported. At grade 2 it considers holding and resuming on symptom control below 10 mg prednisone. SITC states no rechallenge position for PMR. Two facts from SITC's chapter still pull in opposite directions and are both carried rather than resolved: the majority of cases respond well to corticosteroids, the most favorable statement it makes about any rheumatological irAE; and the rare GCA companion risks irreversible visual loss, which is not a risk to run twice without a reason. The stance stays individualized — ASCO permits resumption but conditions it on a specialist consultation this atlas cannot adjudicate.

  • · Giant-cell arteritis excluded, or — if it occurred — treated and considered explicitly, since the harm it threatens is permanent
  • · Symptoms controlled at grade ≤1 and inflammatory markers settled
  • · Rheumatology involvement in the decision

Deliberately not carried

  • Reported frequency — EMPTY, on SITC's own account: it states that assessment of the incidence of PMR is difficult because the majority of studies of musculoskeletal irAEs are observational and retrospective. A card that quietly borrowed the arthritis or arthralgia range would contradict the chapter it cites.
  • Where sources differ — Empty. Only SITC's musculoskeletal chapter is read for this entity — EULAR's chapter is held for myositis only — so there is no second position to compare.
  • Difference between ICI classes — Null for PMR itself. SITC states that GCA has been seen with both PD-(L)1 and CTLA-4 blockade, which names both classes rather than comparing them, and a framing requires a comparison to be a comparison.
  • Grade 3 or higher share — Null. No grade ≥3 rate for PMR is stated in any source cited here, and no incidence is stated at all.
  • Mortality — Null. SITC states that no deaths have been attributed to ICI-induced vasculitis — the family GCA belongs to — but that is a statement about vasculitis, and it is left on that page rather than converted into a mortality framing for PMR.
  • Corticosteroid taper — SITC gives PMR a dose and no taper. Every dosed rung shows ASCO's cross-organ 'at least 4-6 weeks' as an open-ended floor with all three cadence fields null together. Open-ended matters more here than elsewhere: PMR corticosteroid courses are commonly long, and a rendered completion date would be the wrong shape of number.
  • Care setting — No care setting is stated. Outpatient reflects a toxicity SITC manages with oral corticosteroids and a referral; nothing in the chapter admits a PMR patient.
  • Linked society recommendations — Left empty although ASCO and SITC are both in this atlas's guideline library: the recommendation stored against each of them there is scoped to ICI-related kidney injury and would put kidney dosing on a rheumatology card.

Sources

  • Brahmer JR, et al. (2021) Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immune checkpoint inhibitor-related adverse eventsCited for: The PMR symptom pattern and its shoulder-and-hip distribution, the rare accompaniment by giant-cell arteritis and the resulting need to assess visual symptoms, SITC's own statement that the incidence cannot be assessed reliably, the 12-week median onset, the good corticosteroid response, the ESR and CRP evaluation, the same absolute 10-20 / 40-60 mg/day dosing as inflammatory arthritis, the PMR-specific refractory options, and the low threshold for temporal artery biopsy with urgent corticosteroids when GCA is suspected.Supporting text: the full text
  • Schneider BJ, et al. (2021) Management of Immune-Related Adverse Events in Patients Treated With Immune Checkpoint Inhibitor Therapy: ASCO Guideline UpdateCited for: ASCO's Table 5 section 5.3 polymyalgia-like-syndrome chapter, and only that entity: continue the ICPi at grade 1 with acetaminophen or NSAIDs; at grade 2 consider holding with resumption on symptom control below 10 mg prednisone, prednisone 20 mg/d with a taper started after 3-4 weeks if symptoms improve, and escalation after 4 weeks without improvement; and at grades 3-4 — one row — hold with resumption in consultation with rheumatology on recovery to grade 2 or less, noting that toxicity returning on rechallenge has been reported, with prednisone 40 mg/d and a steroid-sparing agent where needed.Supporting text: the full text

ICI-associated sicca syndrome and dry mouth

Also called: sicca syndrome · xerostomia · dry mouth · Sjögren-like syndrome · dry eyes

The irAE most likely to be dismissed as a nuisance and least likely to fully resolve: SITC states that patients who develop sicca often do not recover completely, may need long-term care for salivary hypofunction, and are at risk of losing teeth. It carries the only corticosteroid taper window this organ's chapter actually states — 20-40 mg/day for grade ≥2, tapered over 4-6 weeks — and one trap worth holding onto: the oral corticosteroids used for other irAEs are themselves a risk factor for the oral candidiasis that mimics it.

CommonSeriousonset: weeks 6–12

Reported frequency

  • 3%-24% — Incidence of dry mouth in clinical trials

    of Trials reporting it — SITC notes that many clinical trials did not report dry mouth at all · Reported by SITC from a systematic review. The range is between studies, and the denominator is itself incomplete because reporting was inconsistent — SITC says so, and that qualification is part of the figure

    guideline · 34172516

  • <1% — Sicca accompanied by true Sjögren syndrome

    of A registry study of grade ≥2 irAEs · Reported by SITC. This is the rate of sicca WITH the serology of true Sjögren syndrome (ANA, anti-Ro and/or anti-La) among grade ≥2 irAEs, not the rate of dry mouth — the two figures on this card count different things and are stored separately for that reason

    guideline · 34172516

Onset

SITC states the median time to onset of dry mouth, indicative of sicca syndrome, as 70 DAYS. Seventy days is exactly ten weeks, so the stored median is a unit conversion of the published figure and not an estimate — unlike the Guillain-Barré card, where 'within the first 3 cycles' was refused because a cycle is not a fixed duration.

Presentation

  • · Dry mouth (xerostomia), which SITC says may be an irAE in its own right or a feature of sicca syndrome
  • · Painful oral sores
  • · Dry eyes — the other half of sicca, and the reason this card is cross-tagged to the eye
  • · ANA, anti-Ro and/or anti-La where true Sjögren syndrome accompanies it, which SITC says is rare
  • · Salivary hypofunction that persists, with the dental consequences that follow it

Differential

  • · Oral candidiasis — and the trap SITC names explicitly: oral corticosteroid use, common in patients being treated for other irAEs, is itself a risk factor for it, so the treatment for one toxicity produces the mimic of another
  • · Radiotherapy-induced xerostomia and mucositis in a patient who has had head-and-neck radiation
  • · Pre-existing Sjögren syndrome unmasked rather than caused by the ICI
  • · Anticholinergic and other medication-induced dry mouth, which is common and reversible
  • · Dehydration and mouth-breathing, the ordinary causes that do not need immunosuppression

Work-up

  • Rheumatology, oral medicine or dental consultation · All patients

    SITC's stated first step for possible sicca syndrome, and it names all three specialties rather than defaulting to rheumatology.

    34172516

  • Assessment for oral infection · All patients

    SITC asks for the possibility of infection to be accounted for during diagnosis AND monitoring — not once at the start — because candidiasis both mimics and complicates this toxicity.

    34172516

  • ANA, anti-Ro and anti-La · If atypical

    The serology that distinguishes sicca accompanied by true Sjögren syndrome, which SITC reports at under 1% of grade ≥2 irAEs.

    34172516

  • Dental review · All patients

    Tooth loss is a stated consequence of severe sicca, and the review is what makes it preventable rather than a complication to be noted afterwards.

    34172516

Grade ladder

Grade 1
Continue the ICIOutpatient

Grade 1 — SITC's corticosteroid dose is scoped to grade ≥2 sicca. At grade 1 the management it describes is topical and supportive, and ASCO continues the ICI with close monitoring.

No corticosteroid at this grade

SITC scopes its systemic dose to grade ≥2 sicca syndrome. For initial management of dry mouth or painful sores it describes oral rinses instead — with its own caveat that their evidence comes from radiotherapy-related mucositis and that data are lacking in ICI-treated patients. So this rung is topical and supportive by the chapter's design, not for want of a number.

  • · Oral rinses — doxepin mouthwash, or diphenhydramine-lidocaine-antacid ('magic mouthwash') — for dry mouth or painful sores, carried with SITC's caveat that the supporting data are from radiotherapy-related mucositis and not from ICI-treated patients
  • · Account for oral candidiasis at diagnosis and during monitoring, not only if the rinses fail
  • · Dental review early; the tooth loss SITC describes is a consequence of untreated dryness over time

Escalate when: Symptoms persisting or worsening despite topical measures, or dryness severe enough to affect eating, speech or dentition.

Grade 2
Hold the ICIOutpatient

Grade 2 — the threshold at which SITC's systemic dose applies: patients with grade ≥2 sicca syndrome may be treated with 20-40 mg/day of prednisone equivalents, subsequently tapered over 4-6 weeks. ASCO may suspend the ICI for most grade 2 toxicities.

Corticosteroid 20–40 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks, starting once: SITC's word is 'subsequently' — the taper follows the treatment course, and the chapter states no response marker to gate its start. The 4-6 week window is SITC's own for this entity, which is why it renders with both bounds rather than as ASCO's open-ended cross-organ floor.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

  • · An oral rinse containing dexamethasone may also be considered — SITC's own adjunct alongside the systemic dose
  • · Sialogogue therapy — cevimeline, pilocarpine or other systemic acetylcholinergic agents — carried at the strength SITC gives it: ANECDOTALLY reported as helpful when symptoms are persistent, bothersome and refractory to topical rinses
  • · Continue to account for oral candidiasis; the systemic steroid started here raises that risk rather than lowering it

Escalate when: No improvement across the treatment course, or dental and infective complications developing despite it.

Grade 3
Hold — consider permanent discontinuationOutpatient

Grade 3 — SITC's sicca dose is written for grade ≥2 and does not step up at grade 3, so the band is unchanged; what changes is ASCO's cross-organ instruction to suspend the ICI and the fact that dryness at this severity is what causes the corneal and dental damage the chapter warns about.

Corticosteroid 20–40 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks, starting once: SITC's own window for this entity, following the treatment course; no response marker is stated.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

  • · Specialist care across rheumatology, oral medicine and dentistry rather than any one of them
  • · Ophthalmology where the eyes are involved — severe ICI dry eye can reach corneal perforation, which is stated on the eye side of this chapter
  • · Plan for long-term salivary hypofunction: SITC says full resolution often does not come

Escalate when: Corneal involvement, inability to eat or speak, or infection complicating the dryness.

Grade 4
Discontinue permanentlyConsider admission

Grade 4 — SITC states no separate grade 4 sicca regimen; the band and taper are unchanged from grade 2. ASCO's cross-organ rule is permanent discontinuation at grade 4.

Corticosteroid 20–40 mg/day (oral, prednisone equivalents)

Taper over 4–6 weeks, starting once: SITC's own window for this entity; no response marker is stated.

No step size or interval is carried: the chapter cited does not specify a taper cadence, and one is not invented here.

  • · Permanent discontinuation of the ICI, per ASCO's grade 4 rule
  • · Long-term care for salivary hypofunction and dental protection, which SITC frames as ongoing rather than as part of the acute episode

Escalate when: Already the top rung. No grade 4-specific sicca regimen is stated in the chapter held here.

Rechallenge

Individualize the decision

No source cited here states a rechallenge position for ICI sicca syndrome. What makes this decision unlike the others in the organ is that resolution often does not happen: SITC says patients who develop sicca frequently do not experience full recovery and may need long-term care for salivary hypofunction. So 'resolved to grade ≤1' — the usual precondition — may simply not be available, and the decision becomes one about tolerable persistent symptoms rather than about recovery.

  • · An explicit judgment about persistent symptoms, since full resolution is often not reached and waiting for it may mean waiting indefinitely
  • · Dental and ocular assessment, because the harms that accumulate here — tooth loss, corneal damage — accumulate quietly
  • · Oral infection excluded as a contributor to the symptoms being attributed to sicca

Deliberately not carried

  • Where sources differ — Empty. Only SITC's chapter is read for sicca; the EULAR chapter held here covers myositis only.
  • Difference between ICI classes — Null. No class comparison for sicca or dry mouth is stated in the chapter held here.
  • Grade 3 or higher share — Null. The 3%-24% is all-grade dry mouth and the <1% is sicca with Sjögren serology among grade ≥2 irAEs — neither is a grade ≥3 rate for this entity, and the second is not converted into one.
  • Mortality — Null. No fatality figure for sicca exists in any source cited here, and none would be expected.
  • Corticosteroid taper — The 4-6 week window IS SITC's own for this entity — the only stated taper in this organ's chapter — so it renders with both bounds and is not open-ended. The step size and interval are still empty: SITC gives the window and no cadence, and inventing one would print a number no source states.
  • Corticosteroid taper — newer guidance — SITC's 4-6 weeks stands unopposed. The most recent guidance read for this organ states no taper length for sicca at all: its 3-week taper belongs to lichen planus and to oral mucosa inflammation, and the footnote governing its dry-mouth cell gives a dose escalation and a 14-day futility point without a duration. So there is no newer number to weigh against the one shown — an absence worth stating on a card whose organ has two societies read.
  • Care setting — No care setting is stated. Outpatient reflects a toxicity managed with rinses, an oral steroid and dental review; the grade 4 rung says consider admission on severity alone.
  • Linked society recommendations — Left empty although ASCO and SITC are both in this atlas's guideline library: the recommendation stored against each of them there is scoped to ICI-related kidney injury and would put kidney dosing on a rheumatology card.

Sources

  • Brahmer JR, et al. (2021) Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immune checkpoint inhibitor-related adverse eventsCited for: Dry mouth as an event in its own right or a feature of sicca syndrome, the oral-candidiasis link and the fact that the corticosteroids used for other irAEs are themselves a risk factor for it, the dental consequences up to tooth loss, the 3%-24% incidence range and the under-1% rate of true Sjögren-accompanied sicca, the 70-day median onset, the frequently incomplete resolution, the specialist consultation, the mouth-rinse options with SITC's own caveat that the evidence for them is radiotherapy-derived, the anecdotal status of sialogogues, and the 20-40 mg/day dose tapered over 4-6 weeks for grade ≥2.Supporting text: the full text
  • Schneider BJ, et al. (2021) Management of Immune-Related Adverse Events in Patients Treated With Immune Checkpoint Inhibitor Therapy: ASCO Guideline UpdateCited for: ASCO's cross-organ ladder, cited as that and nothing more. ASCO's Table 5 musculoskeletal chapter IS now held for this organ, per entity, but it has NO section for sicca - its only mention of sicca is a narrative aside in the arthritis discussion, with no management position - so this card reaches ASCO through the cross-organ ladder alone.Supporting text: the PubMed abstract (checkable at the link above)

Spans more than this organ

Triple-M overlap (myositis / myocarditis / myasthenia gravis)

triple M · myositis-myocarditis-myasthenia overlap · overlap syndrome · IM3

When to suspect it

  • Weakness with a raised CK that also carries a troponin rise, a new arrhythmia, ptosis, diplopia or dysphagia — any second organ turns a single-organ toxicity into this syndrome
  • SITC names the three together specifically because their symptoms overlap: limb and bulbar weakness can belong to any of them, and the first-diagnosed is not necessarily the whole picture
  • The pharmacovigilance record found myasthenia gravis distinguished from other neurological events by frequent CONCURRENT myocarditis and myositis — the co-occurrence is measured, not merely plausible
  • 9% of ICI-associated myositis carries myocarditis and 9% carries myasthenia gravis (SITC) — the figures are on the myositis card

Screen for the other members

  • Troponin and EKG · All patients — The myocarditis screen, and the finding that most changes management — myocardial involvement makes ICI discontinuation permanent and carries the syndrome's highest fatality.34172516
  • Creatine kinase · All patients — The myositis marker, with SITC's caveat that it misleads in both directions — asymptomatic with a raised CK, symptomatic with a normal one.34172516
  • Acetylcholine-receptor and MuSK antibodies, with electrodiagnostic studies · All patients — The myasthenia component. Serology can be negative — SITC states toxicity occurs independent of it — and electrodiagnostics separate myasthenia gravis from myositis.34172516
  • Negative inspiratory force and vital capacity · All patients — Both myasthenia gravis and myositis can weaken the diaphragm; respiratory failure is a shared route to death and is not visible on limb strength.34172516

How management changes

Manage to the most dangerous member, not the presenting one. If myocardial involvement is confirmed, the ICI is permanently discontinued (the myositis card's rule) rather than held, and management follows the myocarditis card — coronary care, pulse-dose methylprednisolone, second-line immunosuppression on the 24-hour non-response rule, and caution against infliximab. Myasthenic respiratory compromise is managed with IVIG or PLEX. No source cited here states a combined regimen for the syndrome as a unit; the deviation is to escalate to whichever member's ladder is highest, and each member card carries its own doses.

Rechallenge

Rechallenge is contraindicated — Any myocardial involvement makes discontinuation permanent on the myositis card, and both myasthenia gravis and Guillain-Barré carry contraindicated or discontinue-on-diagnosis stances of their own. The syndrome inherits the most conservative member's position — there is no configuration of the triad that reopens rechallenge, and no source cited here describes resuming an ICI after it.

Sources

  • Brahmer JR, et al. (2021) Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immune checkpoint inhibitor-related adverse eventsCited for: Myositis frequency by ICI class, its association with myocarditis and myasthenia gravis at 9% each, the mechanisms of fatality, the symptom range including the asymptomatic-with-raised-CK and symptomatic-with-normal-CK presentations, the 5-year sequelae figure, and the whole graded ladder — the rheumatology or neurology referral, the rule that grade 1 with raised CK and weakness is managed as grade 2, the grade 3 prednisone dose, the IV methylprednisolone and plasmapheresis or IVIG escalation, the hold-until-grade-1 rule with permanent discontinuation on myocardial involvement, the 4-6 week non-response trigger for steroid-sparing agents, and the rituximab caution.Supporting text: the full text
  • Johnson DB, et al. (2019) Neurologic toxicity associated with immune checkpoint inhibitors: a pharmacovigilance study.Cited for: That myasthenia gravis was distinguished from the other neurological phenotypes by frequent CONCURRENT myocarditis and myositis, alongside its early onset and roughly 20% fatality — the pharmacovigilance evidence that this triad co-occurs rather than being three independent toxicities that happen to share symptoms.Supporting text: the PubMed abstract (checkable at the link above)

Other members: ICI-associated myocarditis, ICI-associated myasthenia gravis

Educational use only. Educational synthesis of the published literature — not a treatment protocol, dosing guide, or medical advice. Regimens and agents shown are illustrative of what the literature describes; verify against current guidelines (ASON / KDIGO / ASCO / NCCN) and individualize to the patient. Using this site creates no clinician–patient relationship.

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