Myocarditis, Myositis, and Myasthenia Gravis: The Complexities of Treating Steroid-Refractory Triple M Syndrome.

BACKGROUND

Triple M syndrome is the combination of myocarditis, myositis, and myasthenia gravis secondary to immune checkpoint inhibitor (ICI) treatment. Traditionally managed with high-dose steroids, ICI myocarditis may benefit from early initiation of nonsteroidal immunosuppression.

CASE SUMMARY: A man with hepatocellular carcinoma presented with double vision and an elevated high-sensitivity troponin after receiving his first dose of tremelimumab (CTLA-4 inhibitor) and durvalumab (PD-L1 inhibitor). He was diagnosed with steroid-refractory ICI myocarditis and treated with abatacept and ruxolitinib. Early recognition of triple M syndrome and initiation of nonsteroidal immunosuppression are described.

DISCUSSION: Management of ICI myocarditis is evolving. Nonsteroidal immunosuppression may become an essential component of management as ICI use, and therefore occurrence of triple M syndrome, increases.

TAKE-HOME MESSAGES: If there is recent initiation of ICI therapy, elevated troponin, and concomitant ICI toxicities, providers should suspect ICI myocarditis despite negative cardiac magnetic resonance imaging. Nonsteroidal immunosuppression with CTLA-4 agonists may be effective in patients treated with CTLA-4 inhibitors.