[Unexplained chronic hypokalaemia in a young woman]

The 27 year old female patient presented with chronic hypokalaemia known for 6 years and current potassium values of 1.8 mmol/l. She reported having diarrhea for a few days, fever was denied.

Physical examination revealed dry skin and mucosa and a slim nutritional status, laboratory investigations showed a hypokalaemic, hypochloraemic alkalosis and hypomagnesaemia. Our first suspicion was an eating disorder or abuse of diuretics or laxatives. Urine analysis showed a high concentration of potassium and chloride, a screening for diuretics was negative. Due to the electrolyte constellation we assumed a Gitelman's Syndrome which was confirmed by genetic testing.

After intravenous substitution of potassium and cessation of diarrhea the potassium values stabilised at 2.5 - 3.0 mmol/l. After being discharged she continued oral substitution of potassium and no such period of severe hypokalaemia occurred again.

Establishing a diagnosis for patients with chronic hypokalaemia may present difficulties. Urine analysis can help to find reasons for electrolyte disorders. Via measurement of urinary chloride concentration repetitious vomiting as stigmatising diagnosis could be excluded. Urine analysis also led to the diagnosis Gitelman syndrome, an inherited renal tubular disorder, which is suspected to count for 50 % of unexplained chronic hypokalemia.