Complete heart block associated with paraneoplastic hypercalcemia: a case report

BACKGROUND: Complete heart block (CHB) means a lack of association between the atrium and the ventricle. Hypercalcemia is an electrolyte disorder that rarely causes CHB. CASE SUMMARY: Hereby, we report the case of a 59-year-old male who was admitted with general weakness. The electrocardiography (ECG) changes revealed CHB, short QT interval due to short ST segment, and generalized ST elevation. The initial calcium level was 15.8 mg/dL (high), and serum levels of parathyroid hormone (PTH), vitamin D, and phosphorus were normal. A chest computed tomography scan showed a large, central mass with cavitation in the right lung. After an initial diagnosis of lung cancer and paraneoplastic hypercalcemia, the patient was treated with normal saline, calcitonin, and zoledronic acid, whose calcium levels decreased to 10.4 mg/dL after 4 days. Pathological ECG findings were also resolved after the correction of serum levels of calcium. DISCUSSION: Hypercalcemia sometimes occurs as a paraneoplastic syndrome following the production of PTH-related peptide by malignant cells, including squamous cell carcinoma of the lung. Complete heart block associated with paraneoplastic syndrome has been reported so far in only one study.