Abstract

AIM. To investigate genetic background and aetiology in Estonian children with hearing loss (HL) and to describe their phenotype.

METHODS. The study group included 233 children with HL. They were investigated by APEX gene array analysis, which covers 201 mutations in eight dif ferent genes (GJB2, GJB3, GJB6, GJA1, SLC26A4, SLC26A5, 12S-rRNA and tRNA (Ser)).

RESULTS. A total of 115 pat ients had a mutation in at least one allele of the GJB2 gene (49%). Seventy-three (31%) were homozygous for the c.35delG mutation and seven (3%) were homozygous for the p.M34T mutat ion. Five pat ients (2%) had congenital cytomegalovirus infection established by DNA analysis. Syndromic HL was confirmed in seven patients. Whole genome array analysis was performed in 28 patients with different developmental problems; in 4 of them we identified four potentially pathogenic chromosomal deletions.

CONCLUSION. The most f requent GJB2 allele causing HL in Estonian children was c.35delG (75%) followed by p.M34T (12%); the other alleles were found rarely (0.2–2%). The etiology of HL was established or specified in 140 investigated children of the study population (60%).