Hereditary non-syndromic hearing loss: influence of different variables

ABSTRACT

Non-syndromic hearing loss [NSHL] was studied in twenty-five patients using a clinical, audiological, cytogenetic and neurobiochemical evaluation. The study group was divided into five subgroups according to severity of hearing loss. Positive parental consanguinity was present in 84% of cases and similarly affected family members were present in 76%. All patients had no congenital malformations and were not dysmorphic. Patients possibly exposed to environmental factors were excluded from the study. Abnormal karyotyping was present in three cases, one case showed chromosome 15p 4, another case showed chromosomal del 11q22.1 and in the third case [47,XY] there was marker chromosome 15. Fluorescence in situ Hybridization [FISH] technique was performed on the case which showed marker. The study group showed significant lowering of five plasma amino acid levels [glutamic acid, aspartic acid, histidine, 3-methylhistidine and carnosine]. There was significant correlation between severity of hearing loss and each of the following patient's age, glutamic acid, aspartic acid, 3-methylhistidine and carnosine. Identification of NSHL early after birth, as well as, amino acid screening is essential, to allow for faster therapeutic intervention and proper genetic counseling