Objective: To determine the spectrum of connexin 26 (Cx26) mutations and th
eir phenotypes in children with sensorineural hearing loss (SNHL) or mixed
hearing loss (MHL).
Design: Children with SNHL or MHL were prospectively tested for mutations i
n the entire coding region of the Cx26 gene.
Patients: Children with SNHL or MHL with no obvious etiology for the hearin
g loss.
Results: Between December 1, 1998, and July 1, 2000, 107 patients with SNHL
or MHL from 99 families underwent Cx26 testing. Most patients were aged 1
week to 16 years (61 boys and 46 girls). Thirty (30%) of 99 probands had Cx
26 mutations: biallelic mutations were detected in 18 (9 homozygous and 9 c
ompound heterozygous) and single mutations were detected in 12. Twelve prev
iously reported mutations (35delG, 167delT, E47X, L90P, M34T, G12V, V37I, R
143W, V84L, V153I, V27I, and 310del14) and 3 novel mutations (E129K, T8M, a
nd N206S) were found. Hearing loss in patients with biallelic Cx26 mutation
s ranged from unilateral high frequency to bilateral profound. Four childre
n, 2 with biallelic mutations, had temporal bone abnormalities.
Conclusions: Connexin 26 mutations are common in children with SNHL, and it
is likely that the homozygous and compound heterozygous mutations cause th
e SNHL. However, pathogenicity is less certain where only a single Cx26 mut
ation is present. Patients with biallelic Cx26 mutations had a slightly hig
her incidence of milder hearing loss than ire previous studies. Children wi
th SNHL or MHL should be tested for Cx26 mutations early in their evaluatio
n.