Refractory Hypocalcemia from Combined Autosomal Dominant Hypocalcemia Type 2 and Postsurgical Hypoparathyroidism

A 49-yr-old female with a history of chronic hypocalcemia, diagnosed twenty years earlier, had serum calcium concentrations that ranged between 6.4 and 8.5 mg/dL (nl, 8.6-10.3 mg/dL) with inappropriately low to low-normal parathyroid hormone (PTH) concentrations. She did not report symptoms of hypocalcemia such as paresthesias, muscle cramping, or tetany. More recently, a thyroid nodule was discovered, and the patient subsequently underwent total thyroidectomy for papillary thyroid cancer. Parathyroid autotransplantation was not performed since parathyroid glands were not identified during the surgery. After total thyroidectomy, the patient developed a more severe symptomatic, refractory hypocalcemia with undetectable PTH concentrations. Postoperative pathologic examination identified a single hypercellular parathyroid gland. Despite medical treatment, including frequent and regular calcium gluconate infusions, serum calcium concentrations remained persistently low. A genetic evaluation identified a pathogenic GNA11 variant (c.178C > T, p.Arg60Cys), consistent with autosomal dominant hypocalcemia type 2 (ADH2). This case expands the understanding of ADH2 and raises important questions about optimal treatment strategies in patients with coexisting genetic and postsurgical hypoparathyroidism.