Metastatic Small Cell Carcinoma of the Bladder Complicated by Paraneoplastic Acute Thrombocytopenia

Small cell carcinoma of the bladder is an extremely rare and aggressive disease with poor overall survival, as it is often diagnosed in later stages. Similarly, paraneoplastic thrombocytopenia is also a rare phenomenon infrequently described in the literature. Given its rarity but responsiveness to chemotherapy, awareness of atypical presentations helps facilitate appropriate treatment. A 76-year-old gentleman was admitted to an Australian regional hospital from a small remote hospital with complaints of five months of anorexia, lethargy, weight loss, and new-onset pleuritic chest pain with a past medical history of prostatomegaly and a distant history of localised seminoma treated with surgical resection and radiotherapy alone. Physical examination revealed new rapid atrial fibrillation and mild hypoxia alongside right upper quadrant tenderness and fullness. The patient underwent pleural drainage, cytology, and computed tomography, was subsequently diagnosed with small cell carcinoma of the bladder, and rapidly developed isolated thrombocytopenia that improved with inpatient chemotherapy with carboplatin/etoposide. He was eventually discharged home after a lengthy admission. On follow-up, he had cycle 2 of treatment as an outpatient before undergoing palliative treatment at the patient's small remote hospital. This highlights the importance of both prompt recognition and treatment of rapidly growing small cell carcinomas when they first present atypically with uncharacteristic paraneoplastic syndromes to reduce morbidity and mortality.