[A Case of Lung Cancer Associated with Drug-Induced Immune Thrombocytopenia]

A Stage IV lung adenocarcinoma was diagnosed in the left upper lobe of an 81-year-old man 2.5 years ago. Following another form of chemotherapy, he then received docetaxel as fourth-line therapy. After 21 days of therapy, although his white blood cell count recovered, his platelet count decreased to 20,000/mL and continued to decrease. Subsequently, he was closely monitored without therapy, and eventually, his platelet count returned within the normal range after 112 days. Blood biochemistry and bone marrow paracentesis findings suggested the presence of paraneoplastic syndrome, idiopathic thrombocytopenic purpura, and drug-induced immune thrombocytopenia. It was difficult to distinguish between the presence of myelosuppression, carcinoma with bone marrow invasion, and paraneoplastic syndrome. This is believed to have resulted from a docetaxel-induced immune thrombocytopenia because, although the platelet count decreased after docetaxel chemotherapy, it eventually returned to normal levels without therapy.