Inheritance of non-syndromal genetic deafness.

This study was carried out on 35 patients with undifferentiated genetic hearing loss attending the Human Genetics Clinic, Medical Research Institute, Alexandria University. Their ages ranged from three months to 25.5 years. Females were commonly affected than males. The high parental consanguinity (75%) with high inbreeding coefficient (0.04) declared the role played by consanguinity, which is an important risk factor, in the occurrence of the abnormality. The type of hearing loss in all patients is sensorineural. The diagnosis of deaf patients was done by means of pedigree analysis and audiometric criteria. They were classified according to their diagnosis into four cases with dominant inheritance, 21 cases having congenital deafness showed recessive inheritance with a recurrence risk of 0.277+/-(1.96) (0.10), one case with childhood deafness also showed recessive inheritance and one case with X-linked inheritance. Six cases were isolated cases, their mode of inheritance was indefinite except one case which may have suggested dominant inheritance. Two cases of ototoxicity in childhood also suggesting genetic causes were included. Genetic counselling was offered to the deaf parents to help the family to accept and adjust to the birth of a deaf child. The nature of the condition, prognosis and recurrence risk were explained to the parents.