Prevalence of the c.35delG and p.W24X mutations in the GJB2 gene in patients with nonsyndromic hearing loss from North-West Romania.

Objective: In Central and South-Eastern European countries, the most frequent mutation types responsible for congenital nonsyndromic sensorineural hearing loss (NSHL) are c.35delG and p.W24X (15-55.8% and 2.5-4.3%, respectively). The aim of the study was to determine for the first time in Romania the prevalence of c.35delG and p.W24X mutations in patients with NSHL.

Material: 75 unrelated children with NSHL from Transylvania (North-West Romania).

Methods: a. Audiological examination (otoscopy, tympanogram, acoustic otoemission and tonal audiogram or auditory evoked potentials); b. detection of the c.35delG (semi-nested-PCR, RFLP and ARMS-PCR analysis) and p.W24X (ARMS-PCR analysis) mutations.

Results: Audiological examination allowed the diagnosis of hearing loss of various degrees: moderate in 8 patients (10.7%), severe in 14 cases (18.7%), profound in 53 patients (70.6%). The number of reported mutation cases as against the number of alleles indicates a 33.3% frequency rate for c.35delG mutation and respectively 5.3% for p.W24X mutation. All 22 patients with 35delG/c.35delG genotype (19 patients), c.35delG/p.W24X genotype (2 patients) or p.W24X/p.W24X genotype (1 patient) presented profound/severe hearing loss.

Conclusion: Our study confirms that the frequency rate of the two mutations analyzed in patients with NSHL from North-West Romania is comparable to that seen in other Central and South-Eastern European countries. The homozygote or compound heterozygote states represent a major risk factor for profound or severe deafness. Audiological screening in newborns and genetic testing in confirmed congenital hypoacusis cases are compulsory for early therapeutic intervention (hearing prosthesis or cochlear implant) and genetic counselling.