A case report of immune checkpoint inhibitor-related steroid-refractory myocarditis and myasthenia gravis-like myositis treated with abatacept and mycophenolate mofetil

Background Immune checkpoint inhibitor (ICI)-related myocarditis is an uncommon but potentially fatal immune-related adverse event. Corticoid-resistant myocarditis induced by ICI is an important therapeutic challenge. Case summary Here, we present a case of steroid-refractory ICI-related myocarditis and myositis treated with abatacept and mycophenolate mofetil (MMF). A 57-year-old mate with metastatic renal cell carcinoma was diagnosed with immune-related myocarditis and myasthenia gravis-like myositis after first dose of combination ICIs with nivolumab (anti-programmed cell death-1) plus ipilimumab (anti-cytotoxic T-lymphocyte-associated antigen-4). Twelve days after ICI he was admitted to the hospital due to palpitations, headache, and pain in the extremities. Laboratory findings revealed elevated inflammatory markers and cardiac enzymes. Electrocardiogram showed first-degree atrioventricular (AV) block and right bundle branch block which developed into complete heart block within 48 h. Because of clinical and paraclinical deterioration despite immediate initiation of methylprednisolone abatacept and MMF was added. Following, gradual subjective improvement and termination of arrhythmia led to discharge of the patient from the hospital 6 weeks after the introduction of ICI. Discussion The key treatment of ICI-related myocarditis is glucocorticoid. For steroid-refractory myocarditis supplementary immune suppressive agents are recommended. Yet, data still relies on case reports and case series, due to tack of prospective studies. In this case, the use of abatacept and MMF led to resolution of steroid-resistant ICI-related myocarditis and myositis.

Automated summary

Immune checkpoint inhibitor (ICI)-related myocarditis is a rare but potentially fatal immune-related adverse event. Glucocorticoids are the mainstay of treatment for ICI-related myocarditis, with supplementary immunosuppressive agents recommended for steroid-refractory cases like the one presented in this case study.