A new study recently published in the Chinese Medical Journal reviewed the diagnostic resources currently available for a mitochondrial disease called mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). The study is entitled “Progress in Diagnosing Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like Episodes” and was conducted by researchers at The First Affiliated Hospital of Dalian Medical University in China.
Mitochondria are small organelles considered the powerhouses of the cells where the energy for the body is produced. Mitochondrial diseases are rare disorders caused by DNA mutations in mitochondrially-expressed genes. One of the most common mitochondrial diseases is MELAS, a progressive neurodegenerative disorder that can affect several body systems, especially the nervous system and muscles. MELAS can have different clinical manifestations and disease course, which often leads to misdiagnosis. Usually, early symptoms of the disease include muscle weakness and pain, exercise intolerance, seizures, recurrent headaches, loss of appetite and vomiting. Individuals severely affected by the disease also experience stroke-like episodes starting before the age of 40. Currently, there is no approved or effective therapy for this disease.
The research team reviewed data from published articles between 1984 and 2014 available in the PubMed database. The search term used was “MELAS” and the articles selected focused primarily on the disease diagnosis based on clinical features, muscle biopsy, blood biochemistry, genetics and neuroimaging.
The team reports that the predominant feature of MELAS is stroke-like episodes. High levels of lactate may also be indicative of the disease. Researchers claim that advanced serial functional magnetic resonance imaging (MRI) is a resource that can provide valuable information for the diagnosis of MELAS, along with muscle biopsy and genetic analysis. Muscle biopsy allows a positive diagnosis through the identification of characteristic ragged red fibers and mosaic appearance of cytochrome oxidase negative fibers. In terms of genetic analysis, it has been previously reported that around 80% of the MELAS cases are due to the mutation m.3243A>G of the mitochondrial transfer RNA (Leu (UUR)) gene (MT-TL1), so genetic test of the mitochondrial DNA sequence can allow a precise diagnosis.
The research team concluded that MELAS can affect multiple systems in the body having a wide heterogeneity of clinical symptoms and recurrent episodes. The team suggests that a MELAS diagnosis should be based on clinical manifestations, serial MRI findings, muscle biopsy and genetic results. The authors believe that all these parameters may help clinicians to make a better early diagnosis of the condition. This is especially important as the prognosis of patients with MELAS is known to be linked to a timely diagnosis.