A Germline ZFX Missense Variant in a Patient With Primary Hyperparathyroidism.

A 51-year-old woman with a history of primary hyperparathyroidism (PHPT) with prior parathyroidectomy, osteoporosis, and learning disability was referred for hypercalcemia discovered after a fall. Family history was negative for PHPT, pituitary, enteropancreatic neuroendocrine, or jaw tumors. Dysmorphic facies, multiple cutaneous melanocytic nevi, café au lait macules, long fingers, and scoliosis were observed. Laboratory evaluation showed an elevated parathyroid hormone (PTH) level, hypercalcemia, and hypophosphatemia, all consistent with PHPT. Preoperative imaging revealed a right inferior candidate parathyroid lesion. The patient underwent right inferior parathyroidectomy with normalization of PTH, calcium, and phosphorus. Genetic testing showed a likely pathogenic de novo heterozygous germline missense variant p.R764W in the ZFX gene that encodes a zinc-finger transcription factor previously shown to harbor somatic missense variants in a subset of sporadic parathyroid tumors. Germline variants in ZFX have been reported in patients with an X-linked intellectual disability syndrome with an increased risk for congenital anomalies and PHPT. Further research may determine if genetic testing for ZFX could be of potential benefit for patients with PHPT and developmental anomalies, even in the absence of a family history of parathyroid disease.