title: Homozygous and compound heterozygous mutations in the ATP6V1B1 gene in patients with renal tubular acidosis and sensorineural hearing loss.
abstract: Distal renal tubular acidosis (dRTA) is characterized by the inability to excrete acid in the renal collecting ducts resulting in inappropriately alkaline urine and hyperchloremic (normal anion gap) metabolic acidosis in the context of a normal (or near-normal) glomerular filtration rate. Inborn dRTA can be due to autosomal dominant or recessive gene defects. Clinical symptoms vary from mild acidosis, incidental detection of kidney stones or renal tract calcification to severe findings such as failure to thrive, severe metabolic acidosis, and nephrocalcinosis. The majority of patients with recessive dRTA present with sensorineural hearing loss (SNHL). Few cases with abnormal widening of the vestibular aqueduct have been described with dRTA. Mutations in three different genes have been identified, namely SLC4A1, ATP6V1B1, and ATP6V0A4. Patients with mutations in the ATP6V1B1 proton pump subunit develop dRTA and in most of the cases sensorineural hearing loss early in childhood. We present two patients from two different and non-consanguineous families with dRTA and SNHL. Direct sequencing of the ATP6V1B1 gene revealed that one patient harbors two homozygous mutations and the other one is a compound heterozygous. To our knowledge, this is the first case in the literature describing homozygosity in the same dRTA gene on both alleles.
authors.affiliation: Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland. nmohebbi@access.uzh.ch
authors.forename: N
authors.initials: N
authors.lastname: Mohebbi
authors.forename: R
authors.initials: R
authors.lastname: Vargas-Poussou
authors.forename: S C A
authors.initials: SC
authors.lastname: Hegemann
authors.forename: B
authors.initials: B
authors.lastname: Schuknecht
authors.forename: A D
authors.initials: AD
authors.lastname: Kistler
authors.forename: R P
authors.initials: RP
authors.lastname: Wüthrich
authors.forename: C A
authors.initials: CA
authors.lastname: Wagner
mesh_terms: D000141:Acidosis, Renal Tubular / Q000235:genetics*; D000328:Adult; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics; D001483:Base Sequence; D002648:Child; D004252:DNA Mutational Analysis; D005192:Family Health; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics*
chemical_list: C509766:ATP6V1B1 protein, human; D001457:Anion Exchange Protein 1, Erythrocyte; C454201:SLC4A1 protein, human; C490181:ATP6V0A4 protein, human; D025262:Vacuolar Proton-Translocating ATPases