The mitochondrial myopathies: 9 case reports and a literature review

Nine cases of mitochondrial myopathy are presented and the literature is reviewed. The clinical picture ranges from virtually pure ophthalmoplegia, through 'ophthalmoplegia plus' to predominantly central nervous system disturbance. Morphological mitochondrial abnormalities are likely to reflect generalised metabolic abnormalities of diverse aetiology, but producing common pathophysiological consequences. The association of mitochondrial myopathy with CNS disorders, which may ante-date muscle weakness, is emphasised. The myopathies constitute a clinical continuum within which the following syndromes may be delineated: (1) Kearns-Sayre syndrome (2) Luft's disease (3) a variant of Ramsay Hunt syndrome (4) relapsing febrile neurological deficits with headache and seizures. These may be specific diseases or artificially separated manifestations of some common metabolic disorder(s). There is a similarity between the CNS pathology, and also some clinical features, of Leigh's disease and the findings in certain of the mitochondrial myopathies. The review suggests that the following should be regarded as associations of mitochondrial myopathy and progressive external ophthalmoplegia (a) diabetes mellitus (b) cataracts, in which calcium deposits may, like basal ganglia calcification, be due to abnormal calcium metabolism. Diplopia, although unusual, does occur in progressive external ophthalmoplegia with mitochondrial myopathy.