Various types of immune related adverse effects (irAEs) are known due to immune checkpoint inhibitor (ICI), and appropriate diagnosis with prompt treatment is necessary. However, myocarditis as an irAE is extremely rare and the symptoms are not characterized. Here, we present a case of myocarditis due to combination therapy of pembrolizumab (PEM) and enfortumab vedotin (EV) which rapidly advanced five days after the administration.

Medical records were retrospectively reviewed.

An 81-year-old woman complained of gross hematuria. CT showed a left renal tumor with infiltration to the renal pelvis. With the preoperative diagnosis of a left renal cell carcinoma cT3aN0M0, a left laparoscopic nephrectomy was performed. However, the pathological diagnosis showed invasive urothelial carcinoma with glandular differentiation. Postoperative CT showed multiple metastasis to bilateral lungs and lymph nodes. EV + PEM was selected as a systemic therapy. Five days after administration, she came to the outpatient unit with complaints of dyspnea on exertion and palpitation. On the same day, she experienced cardiac arrest. Cardiac ultrasonography showed severe hypokinesis, but no significant stenosis of coronary arteries was recognized by coronary angiography. She was admitted to an intensive care unit with percutaneous cardiopulmonary support. With a clinical diagnosis of severe myocarditis due to ICI, steroids, and immune suppressants were administered, and plasma exchange was performed, however, she passed away after 15 days of treatment. The autopsy showed severe necrosis of cardiac muscle.

Dyspnea on exertion after administration of ICI could be a symptom of myocarditis as irAE. Prompt diagnosis with treatment could rescue the patient.