Endocrine Abstracts

We report two brothers diagnosed with familial isolated hyperparathyroidism (FIHP) secondary to a CDC73 gene mutation. CDC73 mutation is a rare yet important cause of early-onset and aggressive hyperparathyroidism associated with parathyroid carcinoma, jaw tumours, and renal or uterine lesions, long-term surveillance for affected individuals is essential. Case 1: An 18-year-old male was referred to the Endocrinology Service following a presentation to a regional hospital with a three-month history of malaise, constipation, PR bleeding, muscle aches, polyuria and polydipsia. Work-up revealed PTH dependent hypercalcaemia, Ca 3.04 (2.15 – 2.50 mmol/l), PTH 2.33 (1.6-6.9 pmol/l). Imaging revealed a left parathyroid adenoma. Sigmoidoscopy showed multiple ulcers. IV zoledronic acid was given pre-op. He underwent partial parathyroidectomy, which was complicated by profound hungry bone syndrome necessitating a prolonged calcium infusion over 21 days and ICU admission. Genetic testing identified a heterozygous CDC73 mutation. Pathology showed a parathyroid adenoma. Case 2: Family screening subsequently identified his 19-year-old brother as asymptomatic but with elevated calcium (Ca 2.98 mmol/land PTH 2.52 pmol/l). Ultrasound confirmed a parathyroid adenoma. He also underwent pre-operative optimisation with IV fluids and zoledronic acid followed by partial parathyroidectomy. Parental genetics were also sent at this time. This case series emphasizes the value of considering genetic causes in young patients with hypercalcaemia and the critical role of family screening and lifelong follow-up in hereditary endocrine disorders.