Abrupt respiratory insufficiency presenting initially as myasthenia gravis crisis with thymic carcinoma – a case report

Abstract

Myasthenia gravis (MG) is frequently complicated by respiratory insufficiency, which is known as an MG crisis. It can appear as the initial presenting symptom of myositis-MG overlap. Here we report a case of a 67-year-old woman with previously underdiagnosed MG, who presented with acute respiratory insufficiency. A bulky mass in the right lung was pathologically suspected to be a lymphoepithelioma-like carcinoma of the thymus. Due to high expression of programmed death-ligand 1 (PD-L1) (70%–80%) on the tumor, the immune checkpoint inhibitor (ICI) pembrolizumab was administered as second-line therapy. However, the patient died of ICI-induced myocarditis, which was confirmed by autopsy. Immunohistochemistry showed an overexpression of PD-L1 on the myocardial sarcolemma as well as the diaphragm. PD-L1 overexpression on the diaphragm might have contributed to the pathogenesis of myositis-MG overlap with acute respiratory insufficiency.