Mitochondrial myopathy with dystrophic features due to a novel mutation in the MTTM gene.
BACKGROUND
A 61-year-old woman with a 5-year history of progressive muscle weakness and atrophy had a muscle biopsy characterized by a combination of dystrophic features (necrotic fibers and endomysial fibrosis) and mitochondrial alterations [ragged-red, cytochrome c oxidase (COX)-negative fibers].


METHODS
Sequencing of the whole mtDNA, assessment of the mutation load in muscle and accessible nonmuscle tissues, and single fiber polymerase chain reaction.


RESULTS
Muscle mitochondrial DNA (mtDNA) sequencing revealed a novel heteroplasmic mutation (m.4403G>A) in the gene (MTTM) that encodes tRNA(Met). The mutation was not present in accessible nonmuscle tissues from the patient or 2 asymptomatic sisters.


CONCLUSIONS
The clinical features and muscle morphology in this patient are very similar to those described in a previous patient with a different mutation, also in MTTM, which suggests that mutations in this gene confer a distinctive "dystrophic" quality. This may be a diagnostic clue in patients with isolated mitochondrial myopathy.
Department of Neurology, Columbia University Medical Center, College of Physicians & Surgeons, 630 West 168th Street, New York, New York, USA.
Lorenzo
L
Peverelli
Carl A
CA
Gold
Ali B
AB
Naini
Kurenai
K
Tanji
H Orhan
HO
Akman
Michio
M
Hirano
Salvatore
S
Dimauro
D004421:Dystonia / Q000150:complications / Q000235:genetics*; D005260:Female; D006801:Humans; D008875:Middle Aged; D017240:Mitochondrial Myopathies / Q000150:complications / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics*
D012343:RNA, Transfer
de novo mutation; dystrophic features; late-onset weakness; mitochondrial myopathy; mtDNA; tRNAMet