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

Tomoyuki Ikeuchi, Katsuyuki Tomita, Hirokazu Touge, Karen Makishima, Masaharu Fukuki, Akira Yamasaki


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.

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Case Reports in Clinical Pathology

ISSN 2331-2726(Print)  ISSN 2331-2734(Online)

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