A case of myasthenia gravis with anti–titin antibody–positive recurrent myocarditis after discontinuation of tacrolimus

Abstract

A 69–year–old man presented with ptosis and diplopia was diagnosed with myasthenia gravis with positive anti–acetylcholine receptor antibodies and malignant thymoma in 2004. The symptoms were subsequently improved by prednisolone and tacrolimus. In January 2021, He was treated with antifungals for chronic necrotizing pulmonary aspergillosis and discontinued tacrolimus because of the unstable blood concentration level. After three months, he was hospitalized for myasthenia gravis crisis with acute myocardial injury. The resumption of tacrolimus with intravenous high–dose immunoglobulin and steroid pulse therapies ameliorated both MG and heart symptoms. After that, anti–titin antibodies were detected. Anti–titin antibodies, a type of anti–striated muscle antibody, have been thought to be involved in the pathogenesis of myocarditis in myasthenia gravis. Anti–striated muscle antibodies may be a predictor of cardiac complications, and measurement of anti–striated muscle antibodies may be useful.