The success of immune checkpoint inhibitors (ICIs) has revolutionized oncology, with an increasing number of patients receiving treatment every year. However, this progress has been accompanied by a rise in immune-related adverse events (irAEs). One such irAE is thrombotic thrombocytopenic purpura (TTP), a rare and potentially life-threatening complication. This report presents a unique case of TTP following a single dose of pembrolizumab, a PD-1 inhibitor. A 76-year-old man with suspected advanced renal cell carcinoma received pembrolizumab as initial treatment. Eleven days later, the patient developed severe thrombocytopenia, bleeding problems, and hemolytic anemia. The following day, ADAMTS13 activity levels were measured at 3.8% (reference range: 40–130%), confirming the diagnosis of TTP. Given the patient’s poor overall condition and limited life expectancy, plasma exchange was not initiated. The patient passed away 15 days after receiving pembrolizumab. This case highlights that even a single dose of pembrolizumab can precipitate TTP, underscoring the need for clinician vigilance. A brief review of previously reported cases of PD-1 inhibitors associated with TTP is included.
Palega et al. (2026) studied this question.