MELAS
MELAS - Mitochondrial Encephalopathy, Lactic Acidosis, Stroke-Like Episodes - mtDNA deletion
Clinical Features
The disease was first described in 1984 as a mitochondrial encephalomyopathy, lactic acidosis with stroke-like episodes, but the genetic defect was only identified in 1990. Only a small part of the patients show the complete clinical picture. Diabetes mellitus and deafness is a frequent manifestation of the disease, but variable additional symptoms, like cardiomyopathy, epilepsy and ataxia might be also present. The onset of the disease can vary from early childhood to adult age. The severity of the symptoms show correlation with the heteroplasmy rate of the mutation, however further genetic and/or epigenetic factors might also influence the phenotype.
Genetic Information
The 3243 A>G mutation in the mtDNA tRNA Leu gene was first described in 1990 by Goto et al.. Less frequently, other mtDNA mutations were also described in patients with the phenotype of a MELAS syndrome.
Prevalence
The prevalence of the 3243A>G mutation in Finnland is 16.3 : 100 000. In another study, in North-East of England the prevalence of all mtDNA mutations was found to be 12.6 : 100 000.
Diagnostic
Indication
Method
1. Mutation analysis of the mtDNA tRNA Leu by DNA sequencing.
2. Mutation analysis for further mtDNA mutations in ND5 and tRNA genes by DNA sequencing.
Sample Requirement
2 - 4 ml of EDTA-blood or muscle DNA
Duration
1 - 2 weeks
OMIM