A Novel CDC73 Gene Mutation in Hyperparathyroidism Jaw Tumor Syndrome Associated With Ectopic-pelvic Kidney

A 21-year-old woman presented with polyuria, fragility fractures, and a history of recurrent renal calculi, which was also present in her maternal aunt. Examination revealed an oval palpable mass in the neck. Biochemistry revealed a grossly elevated serum calcium, PTH, and serum alkaline phosphatase with low serum phosphorous, suggestive of primary hyperparathyroidism. Ultrasonography of the neck and parathyroid scintigraphy localized a large lesion arising from the right posterior and inferior aspect of the thyroid gland, suggesting a parathyroid tumor. Parathyroid carcinoma was suspected based on the severe clinical manifestations. A computed tomography scan of the abdomen revealed cysts in the kidneys, bilateral medullary nephrocalcinosis, left ectopic-pelvic kidney, and lytic lesions in the iliac bone. The patient underwent a right inferior parathyroidectomy with normalization of serum calcium postoperatively. Histopathologic examination revealed a parathyroid adenoma, which was contrary to the expectation. Whole exome sequencing in the index case revealed a novel 99-bp heterozygous insertion, likely pathogenic variant in the exon 2 of CDC73 gene causing hyperparathyroidism jaw tumor syndrome. Here, we report a rare case of hyperparathyroidism jaw tumor syndrome that presented with severe hypercalcemia, renal cysts, and an ectopic-pelvic kidney without jaw tumor or uterine abnormalities.