Frequency of mitochondrial m.1555A > G mutation in Syrian patients with non-syndromic hearing impairment

Mitochondrial maternally inherited hearing impairment (HI) appears to be increasing in frequency. The incidence of mitochondrial defects causing HI is estimated to be between 6 and 33% of all hearing deficiencies. Mitochondrial m.1555A > G mutation is the first mtDNA mutation associated with non-syndromic sensorineural deafness and also with aminoglycoside induced HI. Its prevalence varied geographically between different populations.

We carried out PCR, restriction enzyme based screening, and sequencing of 337 subjects (including 132 patients diagnosed clinically with hereditary deafness) from 54 families from Syria for m.1555A > G mitochondrial mutation.

Mitochondrial m.1555A > G mutation was detected in one of fifty-four families (1.85%), six out of the 132 (4.5%) of all patients with NSHI and one propositus of the 205 individuals with normal hearing (0.48%).

This is the first study to report prelingual deafness causative gene mutations identified by sequencing technology in Syrian families. It is obvious from the results that the testing for the m.1555A > G mutation is useful for diagnosis of hearing loss in Syrian patients and should also be considered prior to treatment with aminoglycosides in predisposed individuals.