Hypokalaemia is one of the commonly encountered fluid and electrolyte abnormalities in clinical medicine, especially in the elderly population. In young adults with persistent hypokalaemia, however, it is important to rule out inherited tubular disorders. The most frequent inherited tubulopathy is Gitelman’s syndrome, an autosomal recessive trait with incidence of 25 per million people. It is due to mutation of SLC12A3 gene, which encodes thiazide sensitive sodium chloride co-transporter (NCC) expressed in the distal convoluted tubule. It is characterized by significant hypomagnesemia, low urinary calcium excretion, and secondary aldosteronism, which is responsible for hypokalemic metabolic alkalosis.
A 25 year old male with a history of gout and traumatic fractures was referred for ongoing issues with headache, fatigue and persistent hypokalaemia in spite of being on a potassium supplement. He was on no potassium depleting agents. Serum potassium was 2.9 mmol/L one year previously. Serum potassium was 3.0 with serum magnesium 0.67 mmol/L (0.7-0.95mmol/L) serum bicarbonate 35 mmol/L (22-26mmol/L) and urinary calcium excretion xx ( RR?). ECG showed sinus rhythm and T-wave flattening. His brother was also found to have hypokalaemia .
A diagnosis of Gitelman syndrome was established. He was treated with oral potassium supplementation (64 mmol/day) and magnesium sulphate 146mg/day. Liberal dietary salt intake was encouraged. of Serum potassium had normalized on 3 months follow-up (3.8 mmol/L).
Gitelman syndrome should be considered in the differential diagnosis of for persistent hypokalaemia, especially in an otherwise healthy young adult.