Genetic Disorders of Membrane Transport III. Congenital chloride diarrhea

Congenital chloride diarrhea (CLD) is a recessively inherited disorder of intestinal electrolyte absorption that involves, specifically, Cl-/HCO-3 exchange. CLD is caused by mutations in a chromosome 7 gene, first known as DRA (for downregulated in adenoma). The disease occurs in all parts of the world but is more common in some populations with genetic founder effects. More than 20 mutations in the gene are known to date. The CLD (or DRA) gene encodes a transmembrane protein belonging to the sulfate transporter family with three known members in humans, all associated with a distinct genetic disease. Members of the gene family can transport other anions as well that may turn out to be physiologically more important than sulfate transport. The gene family is well conserved in many prokaryotic and eukaryotic species and is expected to be much larger than presently known.