Pembrolizumab-Induced Secondary Hypocorticism Manifesting as a Transitory Ischemic Attack

Pembrolizumab is a monoclonal antibody directed against the programmed cell death-1 (PD1) receptor, which binds to PD1 receptors on T lymphocytes and blocks their inactivation by tumor cells. Pembrolizumab is not free from side effects, a rare one of which is hypocorticism. Here we present a patient with pembrolizumab-induced hypocorticism manifested by a cerebrovascular event. The patient is a 67-year-old male with a history of urothelial carcinoma of the left kidney and urothelial carcinoma of the urinary bladder. These malignancies were treated with resection and adjuvant chemotherapy. Pembrolizumab was added 6 months before admission. After the fifth cycle, he suffered loss of appetite, persistent nausea and recurrent vomiting, an itchy rash, expressive aphasia for a few seconds during which he was suddenly unable to pronounce words and sentences, and massive positional vertigo due to arterial hypotension. His serum cortisol level was significantly low. Hypocorticism was successfully treated with hydrocortisone. This case demonstrates that pembrolizumab can be complicated by hypocorticism even after uneventful previous administration and that hypocorticism can manifest with symptomatic arterial hypotension, cerebral hypoperfusion, and positional vertigo. Treating physicians should be aware that secondary hypocorticism is a potentially serious adverse reaction due to the cumulative toxicity of pembrolizumab.