Endocrine Abstracts

A 37-year-old Caucasian man was referred for assessment of borderline hypocalcaemia (2.15 mmol/l) associated with hypophosphataemia (0.32 mmol/l) and elevated serum PTH (145 ng/l). Serum 25OH cholecalciferol was normal (39 mmol/l). Some weeks earlier he had been admitted to hospital as an emergency with severe, colicky right sided abdominal pain. The pain had settled spontaneously and no cause was found. He had subsequently suffered isolated attacks of strangury, dysuria and thought he had passed some grit per urethram. Urine calcium excretion was found to be elevated at 9.5 mmol/l. He had had hypertension for 7 years and this was well controlled with Nifedipine.

Subsequent investigations confirmed the initial findings. In addition, he was found to have mild/moderate hypokalaemia (lowest K⁺3.1 mmol/l) and 1, 25 (OH)₂ cholecalciferol was elevated at 158 pmol/l. The kidneys were of normal size and excretion urography was normal. There was no nephrolithiasis. He had borderline alkalosis (HCO₃ 29 mmol/l). Serum magnesium, renin, aldosterone and uric acid were normal. Screening for renal tubular disease failed to reveal aminoaciduria or urinary β₂-microglobulin. Urinary phosphate excretion was normal. An attempt to reduce urinary calcium excretion with bendroflumethiazide was abandoned because of marked and prompt hypokalaemia.

One possible explanation is that he has a variant of Dent’s syndrome which is an X-linked recessive disorder affecting the proximal renal tubule and is characterised by low-molecular weight proteinuria, hypercalciuria, hyperphosphaturia and nephrolithiasis. Hypokalaemia due to renal potassium wasting is also a common finding and one large case series from UK reported an association in some adults with essential hypertension. Although the unexplained findings of hypokalaemia and hypertension in our case could have been explained by Dent’s syndrome, the absence of low molecular weight proteinuria and of hyperphosphaturia would be atypical.