Asociación de la mutación A1555G del gen MTRNR1 y otosclerosis en una misma familia: diagnóstico diferencial con la otosclerosis coclear

Introduction and objective: The A1555G mitochondrial DNA mutation of the MTRNR1 gene is responsible for sensorineural hearing loss that is accentuated with exposure to aminoglycosides. Otosclerosis is common in our environment. Some patients with otosclerosis have severe impairment of the inner ear. We report a family that had association of otosclerosis and the A1555G mutation that initially were confused with the presence of a cochlear otosclerosis. Method:Ten members of a family with hearing loss, in several of them triggered by aminoglycosides exposition, were included in our study. A clinical and genetic study to rule out the most common mutations involve in hearing loss in Spanish population was carried out. Results: All of them were carriers of the A1555G mutation in homoplasmy. Three had normal audiometry test. Of the remainder, 4 had sensorineural hearing loss for high frequencies and the other 3 had mixed hearing loss that suggesed the presence of otosclerosis. A CT scan of the temporal bone was normal in those three patients. Two patients were treated with a cochlear implant. Discussion: CT is a help to get the difference between cochlear otosclerosis, middle ear otosclerosis and A1555G mutation, and that is very important because people who have this mutation is susceptible to aminoglycoside ototoxicity and besides if they have a severe deafness, the treatment could be a cochlear implant if there are not anatomical abnormalities. Conclusions: In patients with suspected cochlear otosclerosis and maternally history of hearing loss, with a normal CT scan of the temporal bone, the presence of the A1555G mitochondrial DNA mutation should be rudes out. Introducción y objetivo: La mutaciónn A1555G del gen MTRNR1 ADN mitocondrial es responsable de hipoacusia neurosensorial que se acentúa con la exposición a aminoglucósidos. La otosclerosis es frecuente en nuestro medio. Algunos pacientes con otosclerosis presentan afectación severa de oído interno. Se describe una familia con mutación A1555G asociada a otosclerosis, lo que hizo sospechar inicialmente la presencia de una otosclerosis coclear. Material y método: Diez miembros de una misma familia, varios de ellos con hipoacusia subjetiva, en algunos casos desencadenada por aminoglucósidos, fueron incluidos en nuestro estudio. Se les realizó un estudio genético para descartar las mutaciones más frecuentes en la población española. Resultados: Todos ellos eran portadores de la mutación A1555G del gen MTRNR