Pembrolizumab-associated thrombotic microangiopathy in a patient with urothelial cancer: a case report and literature review

Pembrolizumab, a highly selective humanized monoclonal IgG4κ isotype antibody against PD-1, is one of the immune checkpoint inhibitors approved for treatment of various cancers. The most frequent immune-related adverse events include skin, gastrointestinal, and endocrine abnormalities. In rare cases, however, adverse events on the kidney do occur. We here report a case of acute kidney injury presenting thrombocytopenia and hemolytic anemia with the presence of schistocytes, which developed in a 68-year-old man with urothelial cancer, 7 months after initiation of pembrolizumab treatment (10 cycles) and 3 weeks after treatment cessation. The patient had previously undergone unilateral nephrectomy and prior treatment with combined gemcitabine and carboplatin regimen. Although corticosteroid, hemodialysis, and plasma exchange were initiated, the patient died within a few days of respiratory failure. Pathological examination at autopsy revealed multiple carcinomas including the lung, liver, and spine, together with the diagnosis of thrombotic microangiopathy by electron microscopy findings of the renal tissue. To our knowledge, this is the first report describing severe thrombotic microangiopathy in a patient possibly associated with pembrolizumab, leading to death. Physicians should be aware of this potential side effect in patients presenting acute kidney injury and thrombocytopenia.