title: Molecular bases of hearing loss in multi-systemic mitochondrial cytopathy.
abstract: OBJECTIVE
  Hearing loss is a common clinical feature in classic mitochondrial syndromes. The purpose of this study was to evaluate the diverse molecular etiologies and natural history of hearing loss in multi-systemic mitochondrial cytopathies and the possible correlation between degree of hearing loss and neurological phenotype.
  
  
  METHODS
  In this retrospective study we evaluated the clinical features and molecular bases of hearing loss associated with multi-systemic mitochondrial cytopathy. Forty-five patients with sensorineural hearing loss and definite diagnosis of mitochondrial cytopathy according to the published diagnostic criteria were studied.
  
  
  RESULTS
  The sensorineural hearing loss was progressive and for the most part symmetrical with involvement of the higher frequencies. Both cochlear and retrocochlear involvement were found in this cohort. No correlation was found between the degree of hearing loss and the number and severity of neurological manifestations. Deleterious mtDNA point mutations of undisputed pathogenicity were identified in 18 patients. The A3243G mutation was the most frequently encountered among this group. MtDNA depletion, over-replication, and multiple deletions were found in further 11 cases.
  
  
  CONCLUSIONS
  This study reveals an expanding spectrum of mtDNA abnormalities associated with hearing loss. No correlation was found between the degrees of hearing loss and the severity of neurological manifestations.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: Fernando
authors.initials: F
authors.lastname: Scaglia
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Hsu
authors.forename: Haeyoung
authors.initials: H
authors.lastname: Kwon
authors.forename: Ren-Kui
authors.initials: RK
authors.lastname: Bai
authors.forename: Cherng-Lih
authors.initials: CL
authors.lastname: Perng
authors.forename: Hua-Mei
authors.initials: HM
authors.lastname: Chang
authors.forename: Pu
authors.initials: P
authors.lastname: Dai
authors.forename: E O'Brian
authors.initials: EO
authors.lastname: Smith
authors.forename: David A H
authors.initials: DA
authors.lastname: Whiteman
authors.forename: Annette
authors.initials: A
authors.lastname: Feigenbaum
authors.forename: Andrea
authors.initials: A
authors.lastname: Gropman
authors.forename: Lee-Jun C
authors.initials: LJ
authors.lastname: Wong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D028361:Mitochondrial Diseases / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D009154:Mutation
chemical_list: D004272:DNA, Mitochondrial