The hypokalemia mystery: distinguishing Gitelman and Bartter syndromes from 'pseudo-Bartter syndrome'.

The Gitelman and Bartter syndromes (GS and BS, respectively) are characterized by the constellation of hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemic hyperaldosteronism, low to normal blood pressure and juxtaglomerular apparatus hypertrophy. These are due to pathogenic variants in the genes that encode the thiazide-sensitive sodium–chloride cotransporter NCC (SLC12A3) in the distal convoluted tubule or transporters involved in sodium chloride reabsorption in the loop of Henle. ‘Pseudo-Bartter syndrome’ (PBS) is caused by extrarenal or acquired renal salt losses and shares the same plasma electrolyte profile and acid–base disturbances, making the distinction from the genetic forms very challenging. PBS has various etiologies, including diuretic and laxative abuse, self-induced vomiting and the side effects of some antimicrobials. Additionally, congenital chloride diarrhea, cystic fibrosis, Pendred syndrome and chloride-deficient diet can manifest as PBS. In this review we focus on factitious PBS secondary to diuretic abuse, laxative abuse or self-induced vomiting, whereby we point out some clinical and laboratory clues to help clinicians make the correct diagnosis.