Gallbladder carcinoma with hypoparathyroidism-induced hypocalcemia: A rare presentation.

Abstract

Gallbladder carcinoma (Ca GB) is an aggressive malignancy usually diagnosed at advanced stages, with poor prognosis. Hypocalcemia is a known complication in oncology, most often secondary to tumor lysis syndrome, bisphosphonate therapy, or vitamin D deficiency. Hypoparathyroidism-induced hypocalcemia, however, is exceedingly rare and has  not been documented in gallbladder cancer. Case Presentation: We report a 37-year-old male who presented with abdominal pain, jaundice, anorexia, and weight loss. Imaging revealed irregular gallbladder wall thickening extending into the extrahepatic bile duct with partial encasement of the right hepatic artery, consistent with stage T4 Ca GB. He underwent PTBD drainage and received gemcitabine-based chemotherapy. Following eight cycles, he presented with acute bilateral lower limb weakness. Laboratory evaluation demonstrated severe hypocalcemia (serum calcium 4.3 mg/dL), low PTH (13 pg/mL), and low vitamin D (14 ng/mL), consistent with hypoparathyroidism-induced hypocalcemia. He was treated with calcitriol and calcium supplementation, with marked symptomatic improvement. Discussion: While hypocalcemia in cancer patients is common, the etiology is usually multifactorial and rarely due to hypoparathyroidism. Possible mechanisms include autoimmune destruction of parathyroid tissue or cytokine-mediated paraneoplastic effects. Hypoparathyroidism has been reported in thyroid and lung cancer, but not previously in Ca GB. This case highlights the importance of considering endocrine dysfunctions in patients presenting with neuromuscular weakness during cancer therapy. Conclusion: This case represents a rare association of gallbladder carcinoma with hypoparathyroidism-induced hypocalcemia. Early recognition and management are essential to prevent morbidity. Reporting such unique presentations expands understanding of paraneoplastic manifestations in gastrointestinal malignancies.