A case of autoimmune hepatitis with thymoma and myasthenia gravis

A 44-year-old woman presented with cough, facial edema, and progressive fatigue. Computed tomography (CT) showed an anterior mediastinal mass, and laboratory findings showed liver injury. She was diagnosed with thymoma and scheduled for thymectomy after radiation and chemotherapy. However, she was referred to our department due to exacerbation of liver injury. Autoimmune hepatitis (AIH) was suspected based on the findings of elevated anti-nuclear antibody and immunoglobulin G levels. Histological findings of a liver biopsy confirmed the diagnosis of AIH. After oral steroid therapy initiation, she had diplopia and ptosis. Five days after steroid treatment, bulbar symptoms, such as nasal voice and dysarthria, appeared. A physical examination and electrophysiological tests confirmed myasthenia gravis (MG), and to prevent MG crisis, immunoadsorption plasmapheresis and tacrolimus were started by the neurologist. MG symptoms and liver damage gradually improved, she was then treated with chemotherapy and radiation for thymoma and underwent thymectomy, now showing no relapse of AIH or MG. We report the first case of MG developing immediately after the introduction of prednisolone for AIH complicated with thymoma.