Distal renal tubular acidosis in Filipino children, caused by mutations of the anion-exchanger SLC4A1 (AE1, Band 3) gene.

Aim: To describe the clinical features and genetic basis of distal renal tubular acidosis (dRTA) in Filipino children.

Methods: Clinical description and gene analysis of affected members of 7 families.

Results: In all affected children, the disease was associated with mutations of the SLC4A1 gene that codes for the bicarbonate/chloride anion-exchanger 1 (AE1, band 3) protein situated in the red cell membrane and the alpha-intercalated (proton-secreting) cell of the renal collecting duct. In 2 families, affected children were homozygous for a substitution of aspartic acid for glycine in residue 701 of the AE1 protein (G701D); in the other 5 families, affected children were compound heterozygotes of this mutation with the AE1 mutation (Delta400-408) that causes Southeast Asian ovalocytosis (SAO). All affected children had morphological red cell changes that closely resembled SAO, including the children who were homozygous for G701D and did not have the SAO mutation. Homozygous G701D thus produces morphological red cell changes that are not readily distinguishable from SAO. The parents of all 7 families were originally domiciled in the islands of the Visayas group in the central part of the Philippine archipelago.

Conclusion: Recessive renal tubular acidosis in Filipinos is usually caused by SLC4A1 mutations, commonly G701D.