Immune Thrombocytopenia Induced by Nivolumab in a Metastatic Non-Small Cell Lung Cancer Patient

phy and cranial magnetic resonance imaging were performed for staging. The tumor was shown to have invaded the third rib, the pleural nodules, and the left hilar region, revealing cT4N1M1a disease. The tumor did not have an EGFR mutation or ALK translocation. The patient progressed after 3 cycles of paclitaxel and carboplatin and was given single-agent nivolumab (3 mg/kg, every 2 weeks). Pre-treatment platelet counts were normal. At the end of the 6th nivolumab infusion, the platelet count suddenly decreased. Nivolumab was subsequently withheld, but the platelets continued to drop to a nadir of 5,000/mm3. However, leukocyte and hemoglobin levels were normal. The patient had no severe bleeding, bruising, or petechiae during this period. A peripheral smear demonstrated reduced platelets, a few giant platelets, and normal leukocytes/erythrocytes. Platelet transfusions were given for 4 weeks. After 5 weeks of persistent thrombocytopenia, a bone marrow biopsy was performed. This revealed hypercellularity and an increased rate of megakaryocytes. Hence, the patient had isolated thrombocytopenia in the absence of other causes and was diag