Study of a Brazilian Family Presenting Non-syndromic hearing loss with mitochondrial inheritance

Abstract

We hereby report on the audiological and genetic findings in individuals from a Brazilian family, with the following mitochondrial mutation A1555G in the 12SrRNA gene (MT-RNR-1). Nine individuals underwent speech, audiologic (tonal audiometry and logoaudiometry) and genetic evaluations. Eight individuals among the A1555G carriers were affected by hearing impairment and one person had normal hearing thresholds till the end of the present study. The audiologic evaluation results indicated normal hearing thresholds all the way to bilateral profound hearing loss with post-lingual onset and variable configuration. Two affected siblings presented progressive hearing loss. It was impossible to precise the time of hearing loss onset; however, the impairment was present in both children and adults. The genetic study revealed the A1555G mitochondrial mutation in the 12SrRNA gene. Given the prevalence of mitochondrial mutations as a cause of hearing loss, it is fundamental to perform the etiopathologic diagnosis in order to postpone the onset or avoid hearing impairment progression. This kind of hearing impairment represents a challenge to the professionals since there are no physical traits that indicate genetic transmission.

Molecular Investigation of the A1555G Mitochondrial Mutation in Brazilian Patients~!2009-04-10~!2010-01-19~!2010-06-18~!

“…The second study has been carried out in one family only with 9 cases with deafness. The A1555G mutation has been found in all of them, but the association between deafness and use of aminoglycosides was not stablished [28]. Such results, different from the present study, may be explained by the highly heterogeneous ethnic composition of the Brazilian population, due to the miscegenation among several ethnic groups; resulting, thus, in different prevalence in the various Brazilian regions.…”

Etiologic and diagnostic evaluation: Algorithm for severe to profound sensorineural hearing loss in Brazil

“…According to previous studies, this is a common cause of genetic HL in Brazil. It was found in approximately 2% of unselected subjects with HL, and was recommended for inclusion in molecular diagnostic testing for HL (Mingroni-Netto et al, 2001;Pupo et al, 2008b). A lower occurrence of this mutation was observed in the present work, probably because only individuals with severe to profound SNHL participated in the study.…”

Complete Mitochondrial Genome Analysis and Clinical Documentation of a Five-Generational Indian Family with Mitochondrial 1555A>G Mutation and Postlingual Hearing Loss

“…Etiology can be due to genetic or environmental factors or a combination of both; it is broadly divided found in many nonsyndromic hearing loss pedigrees of different ethnic origin with variable clinical phenotypes (Hutchin et al, 1993;Shoffner et al, 1994;Matthijs et al, 1996;ElSchahawi et al, 1997;Gardner et al, 1997;Pandya et al, 1997;Casano et al, 1998;Lehtonen et al, 2000;Malik et al, 2003;Young et al, 2005;Mkaouar-Rebai et al, 2006;Pupo et al, 2008;Bae et al, 2012). On rare occasions, this mutation has also been reported in individuals with Waardenburg syndrome, digital and neural tube defects (Nye et al, 2000;Silan et al, 2011).…”