Hereditary Non-Syndromic Hearing Loss: Influence of Different Variables

Non-syndromic hearing loss (NSHL) was studied in twenty-five patients us- ing a clinical, audiological, cytogenetic and neurobiochemical evaluation. The study group was divided into five sub- groups according to seventy of hear- ing loss. Positive parental consangui- nity 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 ex- posed to environmental factors were excluded from the study. Abnormal karyotyping was present in three cas- es, one case showed chromosome 15p+ , another case showed chromo- somal del 11 q22.1 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 sig- nificant lowering of five plasma amino acid levels (glutamic acid, aspartic acid, histidine, 3-methylhistidine and carnosine). There was significant cor- relation 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 thera- peutic intervention and proper genetic counseling.