Abstract
Objective: 1) Characterize the mitochondrial sequence variants present in a national hereditary deafness DNA repository. 2) Define clinical presentation and audiometric characteristics of the various subgroups.
Method: Retrospective record review of 86 patients with mitochondrial sequence variants compiled in a national hereditary deafness DNA repository from 1997-2008.
Results: Of the 86 patients with mitochondrial sequence variants, 21 (24.4%) had the m. 7445A>G mutation, 18 (20.9%) had the m.1555 A>G, 18 (20.9%) had the m.961 T>G mutation, and 29 (33.7%) had a different mutation at the m961 position, most of which (62%) were the m. 961delT+C(n) variant. The majority of patients had bilateral severe to profound hearing loss. Fifty-three (62%) patients were female and a family history of hearing loss was documented in 60 (69.7%) patients. Deafness was diagnosed before 3 years old in 26 patients.
Conclusion: Mitochondrial deafness can be caused by a variety of genetic mutations with a wide spectrum of clinical presentations. Because of the increased aminoglycoside susceptibility in some forms, it is important to make an accurate diagnosis prior to exposure.
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