Triple M syndrome (myasthenia gravis, myocarditis and myositis) following atezolizumab in small cell lung carcinoma.

An older adult in his early 80s with locally advanced small cell lung carcinoma was treated with carboplatin, etoposide and atezolizumab. After two well-tolerated cycles, he developed acute ocular and neuromuscular symptoms. Investigations revealed features consistent with immune checkpoint inhibitor-related myasthenia gravis, myocarditis and myositis (triple M syndrome). The patient responded to high-dose corticosteroids and pyridostigmine but required prolonged rehabilitation. Notably, he demonstrated an excellent radiological response to systemic therapy. This case highlights the need for vigilance for severe neuromuscular and cardiac immune-related adverse events, the importance of prompt multidisciplinary management, and the clinical paradox of balancing cancer control with life-threatening toxicity.