The coexistence of mitochondrial myopathy and polymyalgia rheumatica without giant cell arteritis is an interesting association. The frequency of this association was assessed in a prospective study.
Muscle biopsy specimens were obtained from 15 patients with polymyalgia rheumatica. When ragged red fibers (RRF) were observed, histochemical, ultrastructural, and biochemical studies were performed.
In five cases, we found the typical appearance of mitochondrial myopathy, with the presence of numerous RRF. Histochemical and biochemical results confirmed these mitochondrial myopathies, showing miscellaneous deficiencies of mitochondrial respiratory chain enzymes.
Persistence of histologic and biochemical abnormalities after steroid treatment in two patients seems to indicate that a subclinical mitochondrial myopathy preceded polymyalgia rheumatica. How a mitochondrial myopathy could induce or facilitate the emergence of a polymyalgia rheumatica remains unknown.