PT - JOURNAL ARTICLE AU - António José Cruz AU - Alexandra Castro TI - Gitelman or Bartter type 3 syndrome? A case of distal convoluted tubulopathy caused by CLCNKB gene mutation AID - 10.1136/bcr-2012-007929 DP - 2013 Jan 22 TA - BMJ Case Reports PG - bcr2012007929 VI - 2013 4099 - http://casereports.bmj.com/content/2013/bcr-2012-007929.short 4100 - http://casereports.bmj.com/content/2013/bcr-2012-007929.full AB - A 32-year-old woman with no significant medical history was sent to our consultation due to hypokalaemia (<3.0 mmol/l). Her main complaints were longstanding polyuria and nocturia. Physical examination was normal. Basic investigations showed normal renal function, low serum potassium (2.7 mmol/l) and magnesium (0.79 mmol/l), metabolic alkalosis (pH 7.54; bicarbonate 32.5 mmol/l), elevated urinary potassium (185 mmol/24 h) and normal urinary calcium (246 mg/24 h). Thiazide test revealed blunted response. Chronic vomiting and the abuse of diuretics were excluded. Genetic tests for SLC12A3 gene mutation described in Gitelman syndrome (GS) came negative. CLCNKB gene mutation analysis present in both GS and Bartter (BS) type 3 syndromes was positive. The patient is now being treated with potassium and magnesium oral supplements, ramipril and spironolactone with stable near-normal potassium and magnesium levels. This article presents the case of a patient with hypokalaemia caused by CLCNKB gene mutation hard to categorise as GS or BS type 3.