Cytopathies mitochondriales et dysfonction des muscles striés squelettiques : le point en 2010

The main role of the mitochondrial respiratory chain is to product adenosine triphosphate (ATP), which is required for metabolic needs of almost all cells of the body. The constituent proteins of the respiratory chain are partly encoded by the mitochondrial genome and partly by the nuclear genes. Mitochondrial cytopathies correspond to a deficiency or a dysfunction of the respiratory chain, resulting in an energetic crisis. Clinical features are highly variable, since many organs or tissues can be affected or alternately only one, such as skeletal muscle. Biological diagnosis is divided in four levels: in vivo functional exploration, biochemical exploration of the mitochondrial respiratory chain, also called OXPHOS system, morphological and immunohistochemical explorations, molecular diagnosis, which implies the study of the two genomes, mitochondrial and nuclear. Isolated strategy is unable to give a diagnosis. The comparison of all results and investigations obtained by the four levels may lead to a conclusion. Mitochondrial disorders take sometimes the appearance of a muscle phenotype: exercise intolerance, myalgia, myoglobinuria. Then, they represent an etiological chapter of the metabolic myopathies. There is also a mitochondrial myotoxicity related to particular drugs.