Endocrine Abstracts

JOINT1851

Familial hypocalciuric hypercalcemia is a genetic condition characterized by mild hypercalcemia, typically found in otherwise healthy and asymptomatic individuals. Differential diagnoses of hypercalcemia are usually based on the acuity and severity of presentation and concomitant level of serum parathyroid hormone. FHH arises from calcium-sensing receptor gene (CASR) mutations, leading to decreased receptor activity in response to serum calcium levels. This results in mild hypercalcemia, hypocalciuria, hypermagnesemia and hypophosphatemia, with normal or slightly elevated serum PTH levels. Here we describe a case of 19 yrs. old male referred by GP for having chronic fatigue for last few months. Initial investigations to find out the cause of fatigue, showed serum calcium level 2.71mmol/l (mildly higher than normal reference range) with normal phosphate of 1.14mmol/l and normal parathyroid level of 4.1 pmol/l. Subsequently, repeat blood test showed phosphate level of 0.77 mmol/l (low) with serum adjusted calcium level of 2.78 mmol/l. Family history includes father having high serum calcium level of 2.8 mmol/l which was not further investigated probably as he was asymptomatic. No other past medical history noted with no history of any current regular medications. He had low vitamin D previously which was treated with prophylactic dose of vitamin D only. His vital signs were stable with BP 118/68 mmhg, Pulse 70/min. Other systemic examination findings were unremarkable. His repeat blood test results in clinic showed Na 140 mmol/l, K 4.3 mmol/l, Creatinine 84 micromol/l, adjusted calcium level of 2.87 mmol/l, phosphate 0.86 mmol/l, 25 hydroxy vitamin D 50 nmol/l, PTH 3.6 pmol/l, TSH 1.6 mU/l, FT4 12.2 pmol/l. Urine test showed urinary calcium creatinine ratio of 0.08, with fasting urine calcium clearance of 0.0020. Considering his positive family history and presentation at an early age, genetic cause was suspected. Hence, a referral for a genetic test has been made. The genetic test results showed heterozygous for pathogenic CASR variant which can cause autosomal dominant familial hypocalciuric hypercalcemia type 1(FHH1). As he was otherwise healthy, reassurance given, and no further investigations or treatment have been offered. This case illustrates the importance of detailed history taking and appropriate clinical evaluation before deciding about further management for asymptomatic mild hypercalcemia. Appropriate clinical history and investigations including early referral for genetic test to diagnose Familial Hypocalciuric hypercalcemia will help to avoid unnecessary medical treatment or parathyroid surgery in selected cases.