[Progressive hearing impairment with deletion in GJB2 gene despite normal newborn hearing screening]

Hearing impairment is the most common sensorineural disease in humans. About 1-3 per 1 000 neonates suffers at birth or in the first years from high-grade to severe hearing impairment. About half of the cases are due to genetic alterations. Most commonly, the GJB2 gene (connexin-26) is concerned with the mutation c.35delG. MATERIAL AND METHODES: All patients showed a severe to profound hearing impairment to the course. DNA isolation, amplification and sequencing was performed using standard techniques.

In the studied patient population we have 142 pa-tients with a homozygous deletion mutation in GJB2 gene (c.35delG) and 29 patients who are heterozygous for this mutation on one allele and heterozygous for another loss-of-function mutation in GJB2 gene. Of these 171 patients were 16 (9.3%) on an inconspicuous newborn hearing screening using Otoacoustic Emissions (OAE). Total was observed a progression of hearing impairment in 31 of these patients (18.1%).

This fact suggests that homozygous deletion mutation c.35delG does not always contribute to an congenital hearing impairment, but to a progressive hearing loss that might develop over the first months and years of life. Additionally, we have to re-evaluate the value of OAE for newborn hearing screening, keeping in mind that one positive result is no warranty for a normal development of hearing function, but a result that should be checked in the course. We recommend annual hearing tests to the paediatrician and with a known familial hearing loss and other risk factors pedaudiological controls.