Muscle disease, HIV and zidovudine: the spectrum of muscle disease in HIV-infected individuals treated with zidovudine.

Eleven patients with AIDS or AIDS-related complex who developed muscle-related symptoms whilst taking zidovudine were investigated. The clinical details of a further ten patients who did not undergo muscle biopsy are also outlined. The clinical features, quantitative muscle strength testing, electromyographic findings, serial creatine kinase levels, muscle biopsy appearance on light microscopy and the effects of zidovudine withdrawal and rechallenge are described. The spectrum of muscle disease encountered included four cases of frank myopathy diagnosed using clinical, electrophysiological and histological criteria, four patients with mild weakness and myalgia in whom muscle biopsies were normal, three patients with myalgia only and a mild increase in the interstitial cell infiltrate shown by biopsy. The patients presenting with myopathy showed no improvement on withdrawal of zidovudine but responded to immunosuppressive therapy with steroids and, in one case, thalidomide prescribed incidentally. At present, it is not yet possible to clinically define a specific zidovudine-induced myopathy that is distinct from the other effects of HIV infection on muscle structure and function. Our experience suggests that zidovudine may be implicated as a myotoxin in some patients, particularly those with myalgia and mild weakness. In those patients with severe weakness, and with biopsy findings of necrosis and inflammation, the drug effects may be difficult to separate from the primary effects of HIV.