Clinical features of the prevalent form of the childhood deafness, DFNB1
, due to a connexin-26 gene defect: implications for genetic counselling.
Across all ethnic groups, the most common carrier frequencies for clinically significant disorders were for cystic fibrosis, DFNB1
nonsyndromic hearing loss and deafness, spinal muscular atrophy, familial Mediterranean fever, Smith-Lernli-Opitz syndrome, sickle cell disease/beta-thalassemia, and Gaucher disease.
In next two years, the first autosomal recessive non-syndromic locus, DFNB1 was mapped in a Tunisian family (Guilford et al.
The loci responsible for autosomal recessive hearing impairment have been designated as DFNB1, DFNB2 an and so on in the same order in which they were reserved or reported.
Genetic analysis of hereditary hearing loss in various populations show DFNB1 as leading cause approximately 30-50%, but DFNB1 mutation is not a major contributor in Pakistani deaf individuals (Santos et al.
Prevalence and evolutionary origins of the del(GJB6-D13S1830) mutation in the DFNB1 locus in hearing-impaired subjects: a multicenter study.
A novel deletion involving the connexin-30 gene, del(GJB6d13s1854), found in trans with mutations in the GJB2 gene (connexin-26) in subjects with DFNB1 non-syndromic hearing impairment.
Ainda para Smith e Van Camp , 50% dos casos de surdez autossomica recessiva podem ser atribuidos a mutacoes no loco DFNB1 (13q11-q12) e o restante aos outros locos autossomicos recessivos.
O loco DFNB1 contem dois genes associados com a DA, o gene GJB2 codificando a conexina 26 (OMIM 12011) e o GJB6 codificando a conexina 30 (OMIM 604418).
E consenso atual que as mutacoes no loco DFNB1 sejam claramente a causa mais comum de DA em muitas populacoes.
For example, the DFNB1 locus is shown to cause both syndromic (Palmoplantar Keratoderma--PPK, Keratitis Ichthyosis deafness--KID) as well as non syndromic hearing impairment.
In autosomal recessive, the first locus DFNB1 (Cx26 gene) was identified in two Tunisian consanguineous families with bilateral profound prelingual hearing impairment (10).