TOXIC MYOPATHIES - ETIOLOGIC, HISTOLOGICAL AND CLINICAL-STUDY OF 74 CASES

BACKGROUND: Toxic myopathies are a frequent cause of acquired myopathy in adults. The type of drugs or toxins involved varies greatly accord ing to the epidemiologic context in which they are evaluated. An etiol ogical, clinical and histological review of the toxic myopathies diagn osed in a group of study of muscular diseases in a third level hospita l was carried out. METHODS: An eight year retrospective study of clini cal and histological review of patients in whom muscle biopsy was perf ormed to diagnose toxic myopathies in the Hospital Clinic i Provincial of Barcelona was performed. RESULTS: The most frequent causes of toxi c myopathy with clinical relevance were those due to the consumption o f zidovudin, ethanol, prednisone, heroin, and neuroleptic, hypolipemia nt and diuretic drugs, with other causes being less frequent. In 52 % of the cases an elevation of muscle enzymes (creatinkinase) was observ ed. In 51 % it was attributed to the administration of a drug at thera peutic dosis, in 34 % to voluntary intoxication (attempt at autolysis or drug dependence) and in 15 % the cases were accidental. The histolo gic study of the muscle biopsy was normal in 10 % of the cases and cha nges indicative of a determined etiology were observed in 65 % and wer e nonspecific in the remaining 25 %. More than a half of the patients were asymptomatic at 3 months of initiation of the symptoms. CONCLUSIO NS: Toxic myopathies often follow a paucisymptomatic form. Most have a nonspecific histologic substrate and improve upon suppression of the producing cause. The performance of muscle biopsy gives positive or ne gative clinically useful information in 60 % of the cases, by discardi ng other possible causes of myopathy.