[Morphological changes of mitochondrial myopathies].

By means of the modified trichromic method of Gomori, introduced by Engel and Cunningham in 1963 [1], it has been possible to demonstrate the presence of ragged-red fibers (RRF) in the mitochondrial myopathies. At present, to study these disorders in muscle biopsies, one may also use morphological, ultrastructural, histochemical, fluorescent, immunological and molecular biology methods. However, the alterations thus demonstrated in striated muscle are not always present in all these diseases due to mitochondrial alterations. At the same time, the multisystemic nature of these diseases also implies alterations in the central nervous system.