An uncommon triad of toxicity: sinus bradycardia, cytopenia and gastrointestinal symptoms induced by thalidomide

Thalidomide, an immunomodulatory and antiangiogenic agent, is widely used in oncology but rarely causes cardiac conduction abnormalities such as sinus bradycardia. Chemotherapy with temozolomide may also result in cytopenia. Early recognition of these adverse effects is critical for patient safety. We report a 50-year-old female with malignant melanoma undergoing chemotherapy with thalidomide (400 mg/day) and temozolomide (150 mg/day) who presented with persistent nausea, recurrent vomiting, generalized weakness, and bradycardia. On admission, vital signs revealed sinus bradycardia (heart rate 40 beats/min) with prolonged QTc, and laboratory findings demonstrated mild anemia, leukopenia, neutropenia, thrombocytopenia, hyponatremia, and borderline hyperkalemia. Imaging and echocardiography were largely unremarkable except for mild tricuspid regurgitation and pulmonary hypertension. A diagnosis of thalidomide-induced bradycardia with chemotherapy-associated cytopenia was established. Thalidomide was discontinued, and the patient received supportive care including intravenous fluids, electrolyte correction, antiemetics, corticosteroids, thyroid hormone replacement, and cardiac monitoring. Atropine was administered for bradycardia as needed. Over 48 hours, the patient’s symptoms and laboratory abnormalities improved, with stabilization of heart rate and resolution of vomiting. This case highlights a rare but significant manifestation of thalidomide-induced sinus bradycardia with cytopenia and gastrointestinal symptoms in a patient receiving chemotherapy for malignant melanoma. Early recognition, prompt drug withdrawal, and comprehensive supportive care were crucial for recovery. Clinicians should remain vigilant for uncommon cardiac and hematologic adverse effects of thalidomide and coordinate multidisciplinary management to optimize patient outcomes.