Pembrolizumab associated immune thrombocytopenia.

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment but are associated with immune-related adverse events (irAEs). Pembrolizumab, an anti-PD-1 antibody, is widely used in non-small cell lung cancer (NSCLC), yet immune thrombocytopenia remains a rare but potentially fatal complication. We report a case of a 55-year-old male with metastatic NSCLC who developed pembrolizumab-associated immune thrombocytopenia. The patient initially responded well to combination therapy with pembrolizumab, carboplatin, and pemetrexed, achieving a metabolic complete response. However, after several cycles, he experienced recurrent grade 3 thrombocytopenia. Immune thrombocytopenia was suspected and managed with corticosteroids, leading to platelet recovery. Upon pembrolizumab rechallenge, thrombocytopenia recurred, necessitating permanent discontinuation of pembrolizumab while continuing pemetrexed maintenance. This case underscores the need for early recognition and prompt management of ICI-induced thrombocytopenia to ensure patient safety while optimizing oncologic outcomes.