Over 40 missense mutations in the gene encoding ROMK, KCNJ1, have been identified and linked to Bartter syndrome type II [4], a rare autosomal recessive disease presenting with fluid loss and electrolyte imbalance, i.e., renal salt wasting, polyuria, early post-natal hyperkalemia and subsequently hypokalemia [119]. The gene discussed is KCNJ1; the disease is Hyperkalemia.