Pembrolizumab: Myositis, myasthenia gravis and myocarditis.

A 79-year-old man developed myositis, myasthenia gravis (MG), and myocarditis (triple M syndrome) while being treated with pembrolizumab for stage IV nonsmall cell lung cancer. He experienced worsening dyspnea and physical examination revealed right ptosis. Further tests showed elevated troponin-I and creatine kinase levels, as well as ECG abnormalities. The patient was admitted to the ICU and received treatment for myocarditis and MG. He was discharged on a methylprednisolone taper and remained stable. The case was reported as an instance of pembrolizumab-induced triple M syndrome, which resulted in third-degree atrioventricular block, left bundle branch block, and complete heart block. [Extracted from the article]