Autosomal Recessive Proximal Renal Tubular Acidosis

Autosomal recessive proximal renal tubular acidosis (AR pRTA) is a rare form of proximal renal tubular acidosis (pRTA; see this term) characterized by an isolated defect in the proximal tubule leading to the decreased reabsorption of bicarbonate and consequentially to urinary bicarbonate wastage along with additional characteristic clinical features.

Epidemiology

The precise prevalence is unknown but it is thought to be a rare disease.

Clinical description

As in other forms of pRTA, hyperchloremic acidosis is a presenting feature and onset usually occurs in childhood. Manifestations include ocular abnormalities (band keratopathy, glaucoma, and cataracts), intellectual disability and severe growth retardation. Other features like dental enamel defects, basal ganglia calcification and pancreatitis are sometimes present.

Etiology

AR pRTA is due to a mutation in the SLC4A4 gene on chromosome 4q13.3 that encodes the electrogenic sodium bicarbonate cotransporter 1 (kNBC1). This protein has three isoforms, with the kNBC1 isoform being expressed in the kidney and eyes.

Genetic counseling

AR pRTA is inherited autosomal recessively and genetic counseling is possible.