Progressive hearing loss, and recurrent sudden sensorineural hearing loss associated with GJB2 mutations--phenotypic spectrum and frequencies of GJB2 mutations in Austria.
Mutations of GJB2 (encoding connexin 26) are the most common cause of hearing loss (HL) in different populations, and a broad spectrum of GJB2 mutations has been identified. We screened 204 consecutive patients with non-syndromic sensorineural hearing loss for GJB2 mutations. Causative GJB2mutations were identified in 31 (15.2%) patients, and two common mutations, c.35delG and L90P (c.269T>C), accounted for 72.1% and 9.8% of GJB2 disease alleles. In four additional patients (2.0%) only one recessive GJB2 mutation was identified, making genetic counselling difficult. No genotype-phenotype correlation was established. We found, however, that homozygotes for truncating mutations were more likely to have a more severe degree of HL compared with other genotypes. Moreover, we showed by co-segregation studies that L90P is a GJB2 disease allele, and that compound heterozygotes for L90P and any recessive mutation share a mild to moderate phenotype. GJB2-associated HL was linked with progressive HL or with recurrent sudden sensorineural hearing loss (SSNHL) in three of 15 cases being analysed retrospectively. We extended the phenotypic spectrum of GJB2-related disease and recommend GJB2 mutation screening also in cases of progressive HL, and recurrent SSNHL. In addition, a carrier frequency of 1/110 (0.9%) for the most common Caucasian mutation in this gene, c.35delG, was determined in 1,212 blood donors from West-Austria, supporting the prevailing hypothesis of a Mediterranean founder mutation. Based on population and patient data, an overall GJB2 mutation carrier frequency of 1.3% was estimated for West-Austria.
Institute of Medical Biology and Human Genetics, University of Innsbruck, Schöpfstr. 41, A-6020 Innsbruck, Austria. Andreas.Janecke@uibk.ac.at
Andreas R
AR
Janecke
Almut
A
Hirst-Stadlmann
Barbara
B
Günther
Barbara
B
Utermann
Thomas
T
Müller
Judith
J
Löffler
Gerd
G
Utermann
Doris
D
Nekahm-Heis
D000293:Adolescent; D000328:Adult; D001317:Austria; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D018450:Disease Progression; D005260:Female; D005787:Gene Frequency; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012008:Recurrence
D017630:Connexins; D017931:DNA Primers; C000607042:GJB2 protein, human; D000072259:Connexin 26