Genetic Testing to Identify Deaf Newborns

Late postnatal onset of hearing loss due to GJB2 mutations

“…unrelated) children homozygous for the 35delG mutation, documented to have normal hearing early in infancy with a later diagnosis of severe hearing loss. One child had a normal result on the newborn ABR screening test and a subsequent ABR at 15 months age obtained on parent's request indicated no responses at 90 dB [23]. Sibling 2 in the present report was similar to this case, with a similar age of diagnosis although the initial ABR showing near normal hearing (in Sibling 2) was done later, at 6 months of age.…”

“…Sibling 2 in the present report was similar to this case, with a similar age of diagnosis although the initial ABR showing near normal hearing (in Sibling 2) was done later, at 6 months of age. The second child reported by Green 2000 was documented to have normal free field audiogram at 5 months of age, and had confirmed severe hearing loss on ABR, 4 months later [23]. Comparatively, sibling 1 in the present report had normal hearing documented on a behavioural test twice, at 2 years 3 months and 2 years 8 months and describes the latest reported age of onset for GJB2 related hearing loss.…”

GJB2 and GJB6 Mutations

“…[16][17][18] Furthermore, the M34T allele has been observed in the general population with a high frequency of 1.2% to 1.5%. 15,19 This high allele frequency was confirmed in a large study 20 of the general population of the South of France (81 of 7032 chromosomes) and in a study 18 of normal-hearing individuals (4 of 232 chromosomes). Because M34T allele frequency is not significantly higher in patients with hearing loss than in the general population, this suggests that M34T is a common polymorphism.…”

Phenotype/Genotype Correlations in a DFNB1 Cohort With Ethnical Diversity

“…Some important gaps in our knowledge of DFNB1 have only become evident after studies combining universal newborn hearing and mutational screening. Most studies have shown that DFNB1 can be congenital, but this and other series 14,40 have reported on neonates with documented normal hearing tests at birth who were later diagnosed with severe or profound GJB2 deafness. Given the observed variability of DFNB1 in terms of the audiological profile (mild to profound, congenital vs. postnatal, bilateral vs. unilateral, stable vs. progressive HL), providing prognostic information regarding hearing impairment may be difficult in some cases.…”