Antiepileptic drug myopathy

Toxic myopathies: muscle biopsy features

Several drugs and toxic substances can cause muscular abnormalities and are frequent causes of acquired myopathies. We present a series of 32 patients, predominance of young adult patients, diagnosed with toxic myopathy. The most common substances inducing myopathy were corticosteroids (56.2%) followed by the propoxyphene, neuroleptics, zidovudine and drug-induced hypokalemia. The investigation showed normal serum creatine kinase levels in 65.4%, myopathic pattern of the needle electromyography in 40% and the more frequent histological diagnosis of the muscle biopsy was type 2 fiber atrophy (59.3%). Clinical features, etiology, course of the disease, serum levels of muscular enzymes, electromyographic features and, especially, muscle biopsy features are discussed.

Iatrogenic and toxic myopathies

There has been increasing awareness of the adverse effects of therapeutic agents and exogenous toxins on the structure and function of muscle. The resulting clinical syndrome varies from one characterized by muscle pain to profound myalgia, paralysis, and myoglobinuria. Because toxic myopathies are potentially reversible, their prompt recognition may reduce their damaging effects or prevent a fatal outcome. Interest in the toxic myopathies, however, derives not only from their clinical importance but also from the fact that they serve as useful experimental models in muscle research. Morphological and biochemical studies have increased our understanding of the basic cellular mechanisms of myotoxicity. Toxins may produce, for instance, necrotizing, lysosomal-related, inflammatory, anti-microtubular, mitochondrial, hypokalemia-related, or protein synthesis-related muscle damage.

Phenytoin-induced dermatomyositis: case report and literature review

A muscle biopsy done to evaluate for ragged red fibers in a patient with progressive myoclonic epilepsy unexpectedly showed prominent inflammation and perifascicular atrophy. Brain biopsy demonstrated Lafora bodies. Lafora body disease is a progressive, fatal myoclonic epilepsy presenting usually in the first or second decade with mental regression, generalized and myoclonic seizures,1,2 ataxia, spasticity, and involuntary movement. It is an autosomal recessive3 disorder localized to chromosome 6q. Phenytoin is herein implicated in the pathogenesis of dermatomyositis.