BSND and Bartter syndrome: Bartter syndrome is a rare genetic disorder caused by mutations in genes that encode various components of the renal tubular transport system, such as K+ channel (KCNJ1 gene), Cl– channel (CLCNKA and CLCNKB genes), their cotransporters (SLC12A1 gene), subunits of these channels (BSND gene), or regulators of the expression of certain transport channels (MAGED2 gene).