Abstract
In 2010, a 48–year–old woman underwent extended thymectomy and radiation therapy for treatment of thymoma. In 2011, she came to our department because of ptosis and muscle weakness in her upper limbs and was diagnosed with generalized myasthenia gravis (MG) on the basis of an anti–acetylcholine receptor antibody level of 85 nmol/L. She underwent corticosteroid pulse therapy and plasma exchange, and her MG symptoms gradually improved. Subsequently, she was in remission for over 10 years under treatment with small amounts of dexamethasone and tacrolimus. In October 2021, she received combination anti–programmed cell death protein–1/CTLA–4 antibody therapy after surgical treatment for stage IV transverse colon cancer at our Department of Surgery. Then, she presented with generalized muscle weakness with elevated serum creatinine kinase, ptosis, and worsening of swallowing function and was diagnosed with myositis and MG crisis as an immune–related adverse event (irAE). The dexamethasone dosage was increased, and intravenous immunoglobulin was administered ; however, respiratory failure progressed, and she was placed on an artificial ventilator. On day 12 after the start of symptoms, hematemesis occurred, and upper endoscopy led to a diagnosis of gastroenteritis as an irAE. Thereafter, liver enzymes rapidly increased, and because no other diseases were involved, a diagnosis of hepatitis by an irAE was made. Plasma exchange therapy was performed, but the patient did not respond to treatment, and oral mycophenolate mofetil for hepatitis was not effective. She subsequently developed pneumonia due to cytomegalovirus and died on day 94 after the start of symptoms. This case highlights that physicians must be aware that patients with MG may experience a variety of irAEs when treated with immune–checkpoint inhibitors, even when they are in remission.
