Michael Chidi Ukaegbu, Clement Nwawolo, Tobechukwu E. Okeke, Patricia O. Iheme, Jamey P. Mairiga


Background: Connexin 26 mutation is known to cause non-syndromic sensorineural hearing loss (SNHL) in many populations however, mutation differs according to races. The objectives of the study are to determine the distribution of Non-syndromic SNHL by mode of inheritance, severity of hearing loss, frequency of hearing loss, age of onset and also determine the contribution of CX 26 and CX 30 genes mutation in pathogenesis of Non-syndromic SNHL in Lagos State Nigeria.

Materials & Methods: Patients who registered for hearing loss treatment at Ear Nose and Throat unit (ENT) of Lagos University Teaching Hospital (L.U.T.H), Idi-Araba Logos Nigeria from January 01, 2020 to December 31, 2021 were enrolled for the study. This study examined the mode of inheritance of non-syndromic SNHL using three generations pedigree. Data on the age, sex, region of the country where the patient comes from, age at onset of hearing loss, number of affected ears and family history of the patients were obtained through a structured questionnaire. Individuals whose hearing loss was as a result of environmental influence were excluded. The frequency and severity of hearing loss was obtained from the pure tone audiometry.

Results: A total of 148 patients (98.7 %) had autosomal recessive mode of inheritance while only 2 patients (1.3 %) had autosomal dominant mode of inheritance. None had neither maternal nor sex-linked mode of inheritance. Among the 102 patients that did audiological evaluations (48 did not undergo audiological evaluations), 43 patients (42.1 %) had moderately severe SNHL, 28 (27.4 %) had severe SNHL, 24 (23.5 %) had profound SNHL, 7 (6.8 %) had moderate SNHL while none had mild SNHL. Fifty four patients (53 %) had high frequency SNHL, 30 (29.4 %) had middle frequency SNHL while 18 (17.6 %) had low frequency SNHL.

Conclusion: The results of the study demonstrate that autosomal recessive mode of inheritance is the commonest mode of inheritance of non syndromic SNHL in the studied population. A novel mutation, Leu 56 His which caused non-syndromic SNHL, was discovered through sequencing.


Gap junction beta 2 gene; Connexin 26; Autosomal recessive non syndromic hearing loss; Deafness; Mutation.

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