Mitochondrial diseases are a heterogeneous group of disorders caused by alterations in mitochondrial DNA (missense mutations, sporadic large-scale deletions or mutations in nuclear maintenance genes). In these rare and complex diseases, symptoms can vary from person to person and between different tissues in a individual. More than 350 genes have been identified.
A team of French clinicians involving doctors from the Institute of Myology report the case of a 34 year old patient with highly asymmetric segmental and oculomotor muscle damage. Biochemical and genetic analyses of mitochondrial DNA were instrumental in explaining this exceptional presentation.
This case demonstrates that the highly asymmetric distribution of muscle wasting correlates with levels of heteroplasmy that can vary drastically for a given muscle type. The authors suggest that this is a new pathophysiological mechanism that may explain the asymmetry in hereditary myopathies.