Objective: To analyze GJB2 235delC monoallelic mutation carrier individuals and test the possible presence and incidence of audiometric abnormalities among 30-60 years old carriers of the 235delC mutations.
Methods: A total of 32 unrelated subjects with nonsyndromic hearing loss were screened for the 235delC mutation. Tonal audiometric analysis was performed on the 235delC mutation carrier group and on a non-carrier control group.
Results: Audiometric evaluations in the control group showed the presence of thresholds within normal limits at all frequencies, while carriers of the 235delC mutation presented with decreased hearing at 1000 Hz and 2000 Hz (age 40-49 years and 50-59 years), and 4000 and 8000 Hz (age 30-59 years), P < 0.05. The hearing loss of carriers gradually increased with age.
Conclusions: GJB2 235delC heterozygous carriers may be a risk group for high-frequency hearing loss. Hearing thresholds may deteriorate in the intermediate frequencies over the age of 40.