Screening for the mitochondrial A1555G mutation among Egyptian patients with non-syndromic, sensorineural hearing loss.

Background & aim: Hearing loss is the most frequent form of neurosensory deficit in humans. Although the majority of hereditary hearing loss is due to nuclear gene mutations, it has become clear the significant contribution of mitochondrial genes. The first mitochondrial mutation shown to cause non-syndromic hearing loss in humans was the A1555G mutation in the small ribosomal RNA gene (12S rRNA). It has been detected in hundreds of families of different ethnic backgrounds, making it one of the prevalent genetic causes of hearing loss currently identified. However, there are major differences between ethnic groups regarding the frequency of this mutation. Few studies have been made in Arab countries, especially in Egypt. Here we report the prevalence of the mitochondrial mutation A1555G among patients with non-syndromic hearing loss (NSHL) and in healthy individuals with normal hearing in the Egyptian population.

Subjects & methods: The study was conducted on 97 patients with SNHL and 300 unrelated healthy Egyptian individuals, with normal hearing, as normal control subjects. Polymerase chain reaction followed by restriction enzyme digestion was used to screen the DNA samples of all subjects for the A1555G mutation.

Results: Participants included 97 cases with SNHL, 46 males and 51 females. Their ages ranged from 1 month to 65 years with the mean age 6.2 years (SD ± 8.2). Paternal consanguinity was reported in 46% (35/76) of the studied families. The A1555G mutation was found in one of the 97 patients (1.3%), while it has not been detected in the 300 control samples.

Conclusion: Our findings indicate that, even in absence of exposure to aminoglycosides, the mitochondrial A1555G mutation is one of the potential causes of non-syndromic SNHL in the Egyptian population.