Renal Tubular Acidosis, Proximal, with Ocular Abnormalities and Mental Retardation

Alternative Names

  • RTA, Proximal, Autosomal Recessive
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Other congenital malformations

OMIM Number

604278

Mode of Inheritance

Autosomal Recessive

Gene Map Locus

4q13.3

Description

The symptoms of proximal RTA with ocular abnormalities and mental retardation include severe hyperchloremic acidosis, keratopathy, low renal threshold for bicarbonate reabsorption, nystagmus, cataract, glaucoma, growth, and mental retardation.

Diagnosis can be made on the basis of the presence of symptoms as well as biochemical indicators. These symptoms and complications are treated symptomatically when possible.

Molecular Genetics

roximal renal tubular acidosis (pRTA) with ocular abnormalities is caused by mutations in the SLC4A4 (NBC1) gene. Studies indicate that at least 50% reduction of SLC4A4 activity is required to cause severe proximal renal tubular acidosis. The protein encoded by SLC4A4 plays an essential role in bicarbonate absorption from renal proximal tubules, and the gene is widely expressed in several ocular tissues. The latter notion may explain the accompanying ocular abnormalities.

Epidemiology in the Arab World

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Subject IDCountrySexFamily HistoryParental ConsanguinityHPO TermsVariantZygosityMode of InheritanceReferenceRemarks
604278.1.1United Arab EmiratesUnknown Renal tubular acidosis; Ocular hyperten...NM_001098484.3:c.2230G>AHomozygousAutosomal, RecessiveAl-Shamsi et al. 2016

Other Reports

Jordan

Horita et al. (2005) identified three new missense mutations in NBC1 from patients with pRTA and ocular abnormalities. One of these mutations was uncovered in a 12-year-old Jordanian (Bedouin) girl born to consanguineous first-cousin parents. She had a severe pRTA with growth delay and ocular complications. Her height (130 cm) was less than the third percentile and she was operated on for glaucoma and cataracts. The patient was found to have the missense c.2643C>T mutation leading to p.R881C in the Na+-HCO3? co-transporter.

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