Mutations in adenosine triphosphate ATP6V1 (B1 H<sup>+</sup>-ATPase subunit), ATPV0A4 (a4 H<sup>+</sup>-ATPase subunit), SLC4A1 (anion exchanger 1), and FOXI1 (forkhead transcription factor) cause distal renal tubular acidosis type I. Carbonic anhydrase II mutations affect several nephron segments and give rise to a mixed proximal and distal phenotype.