Which salt wasting nephropathy resembling Gitelman syndrome is associated with seizure and ataxia?
EAST syndrome (epilepsy, ataxia, sensorineural deafness, and tubulopathy) features renal salt wasting and electrolyte imbalance. The mode of inheritance is autosomal recessive and consanguinity has been described in some families. The responsible gene, KCNJ10 , is expressed in the basolateral membranes of the DCT, connecting tubule (CNT) and CD epithelia. The identified electrolyte and acid–base abnormalities are similar to those seen in Gitelman syndrome and include hypokalemia, hypomagnesemia, and metabolic alkalosis (see Table 72.2). Renin and aldosterone levels are both elevated. Patients typically crave salt, suggesting that they compensate for renal salt losses with an increased consumption of salt to maintain normal blood pressure values. In vitro studies suggest that loss-of-function mutations in KCNJ10 impair the activity of the Na-K-ATPase in the DCT (by decreased potassium “recycling”), located at the basolateral membrane of epithelia. The additional features seen in this syndrome are due to the expression of KCNJ10 in neuronal tissues and in cells of the inner ear.
