is a group of similar kidney disorders that cause an imbalance of potassium, sodium, chloride, and other molecules in the body. In some cases, the condition manifests before birth with increased amniotic fluid surrounding the affected fetus (polyhydramnios). Affected infants typically do not grow and gain wait as expected. Dehydration, constipation and increased urine production result from losing too much salt (sodium chloride) in the urine, and weakening of the bones can occur due to excess loss of calcium. Low levels of potassium in the blood (hypokalemia) can cause muscle weakness, cramping, and fatigue. It is caused by mutations in any one of at least 5 genes and is inherited in an autosomal recessive manner. The different types of Bartter syndrome are classified according to the specific gene that causes the condition. Treatment depends on the type of the syndrome present but chiefly focuses on preventing the loss of too much potassium from the body. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.