MtDNA population variation in Myalgic encephalomyelitis/ Chronic fatigue syndrome in two populations: a study of mildly deleterious variants, by Marianne Venter, Cara Tomas, Ilse S Pienaar, Victoria Strassheim, Elardus Erasmus, Wan-Fai Ng, Neil Howell, Julia L Newton, Francois H Van der Westhuizen, Joanna L Elson in Scientific Reports 2019; 9: 2914 [Published online Feb 27 2019]
Myalgic Encephalomyelitis (ME), also known as Chronic Fatigue Syndrome (CFS) is a debilitating condition. There is growing interest in a possible etiologic or pathogenic role of mitochondrial dysfunction and mitochondrial DNA (mtDNA) variation in ME/CFS.
Supporting such a link, fatigue is common and often severe in patients with mitochondrial
disease. We investigate the role of mtDNA variation in ME/CFS. No proven pathogenic mtDNA mutations were found. We then investigated population variation. Two cohorts were analysed, one from the UK (n = 89 moderately affected; 29 severely affected) and the other from South Africa (n = 143 moderately affected).
For both cohorts, ME/CFS patients had an excess of individuals without a mildly deleterious population variant. The differences in population variation might reflect a mechanism important to the pathophysiology of ME/CFS.
In conclusion, this is the first paper to demonstrate mitochondrial genetic differences between ME/CFS patients and controls. It also demonstrates the power of mtDNA analysis focused on variants likely to be of a functional effect to detect differences between case and control cohorts where the traditional haplogroup association method frequently fails to do so.
Future studies need to include larger cohorts from multiple centres, within and between nations, with standardized sample handling. These studies need to take a multi-disciplinary approach linking genetics, including mtDNA copy number analysis and bioenergetics. Given the changing nature of the disease, longitudinal studies would seem to be essential to further understanding by allowing us to determine how mtDNA varation and mitochondrial dysfunction relates to fluctuations in symptom severity.