Endocrine Abstracts

Background: Familial hypocalciuric hypercalcemia (FHH) is a rare disorder inherited as an autosomal dominant trait, characterized by an inactivating mutation in the calcium-sensing receptor (CASR) gene. This most often presents clinically as a mild, persistent, and asymptomatic hypercalcemia with normal to mildly elevated serum parathyroid hormone, which rarely requires management with pharmacologic agents^[1].

Case Presentation: We present a case of a 36 years old female who presented with 3 months history of polyuria and polydipsia along with worsening joint pains on the background of Ehlers Danlos syndrome. She was found to have moderate hypercalcemia of 3.24 mmol/l (normal range: 2.20-2.60 mmol/l) with borderline raised parathyroid hormone of 7.5 pmol/l (normal range:1.3–7.3 pmol/l) and adequate Vitamin D of 71.1 nmol/l. Her urinary calcium creatinine excretion ratio was low, in keeping with FHH. She had genetic testing which was consistent with Familial hypocalciuric hypercalcemia type 1. Over the course of few months, her symptoms and hypercalcemia did not improve despite adequate fluid resuscitation and IV Zolendronic acid. She had ultrasound neck and Sestimibi parathyroid scan to pick up any coexisting parathyroid adenoma, which came back negative. Her ultrasound renal and bone densitometry did not show any evidence of end organ damage. Eventually she was commenced on cinacalcet 30 mg twice daily which led to normalisation of hypercalcemia and the symptoms over the next few weeks.

Conclusion: This case highlights the diagnostic and management challenges posed by such presentation which is usually not expected in patients with Familial hypocalciuric hypercalcemia. This shows that FHH can present with moderate symptomatic hypercalcemia which require pharmacological intervention.

Reference: 1. Kurian, R., Chandrashekar, G.M., Chandra, L., Kant, R., Chandrashekar, G. and Antony, M.A., 2021. Severe symptomatic hypercalcemia in a patient with familial hypocalciuric hypercalcemia. Cureus, 13(11).