Endocrine Abstracts

It is estimated that one episode of severe hypokalaemia will occur each week, in a hospital serving a population of 150 000. Proper management of hypokalaemia is important as severe forms may cause fatal cardiac dysrhythmias. However, recognition of hypokalaemia may be difficult as it is mild in the majority and also asymptomatic. We present a patient who was had asymptomatic hypokalaemia, with an identical twin with a similar problem.

A 45-year-old previously well woman presented with asymptomatic hypokalaemia. She had a twin sister who had type 1 diabetes and was on potassium supplements for significant hypokalaemia (she refused further investigations and died of unknown causes elsewhere). She was on Sando K and Factor 50 (no incriminating chemicals) prescribed for chloasma, and denied the use of other prescription or proprietary medication. She was normotensive, her systems examination was normal, and there were no signs of endocrinopathy. Investigations confirmed significant hypokalaemia while on supplements – 2.5–2.7 mmol/l; inappropriate urinary potassium loss (113 mmol/24 h); low magnesium of 0.53 (0.7–1 mmol/l); normal suppression of cortisol after overnight dexamethasone; normal aldosterone and renin levels (while hypokalaemic); normal renal, bone and liver profiles. Arterial pH was 7.476, bicarbonate 30.4 and base excess was 6.8. Molecular analysis demonstrated a SLCA123 mutation.

Hereditary ‘channelopathies’ should be considered in subjects with hypokalaemic alkalosis after excluding vomiting, upper gastrointestinal loss, Conn’s syndrome and diuretic use. Our patient had the common mutation associated with Gitleman’s syndrome – incidence about 25/million population, and presents usually in asymptomatic adults. Aldosterone and renin were relatively normal in our patient as she was profoundly hypokalaemic. Her electrolytes normalized on magnesium supplements and spironolactone. The cause for her twin sister’s hypokalaemia is speculative as she refused investigations.