Noninfectious environmental agents associated with myopathies

Increasing attention is being focused on environmental agents as possible factors in the etiology of certain connective tissue disorders. As our awareness in this area increases, the number and diversity of these agents is expanding yearly and now includes, in addition to infectious agents, a variety of foods and dietary supplements, drugs, occupational and other toxic exposures, biologics, and medical devices. Some of these agents have been associated with the development of muscle disease through mechanisms that involve alterations in the vascular supply to muscle, depletion of electrolytes, direct toxic effects on mitochondria or other metabolic processes, or activation of the immune system. Individual host susceptibility factors, including preexisting organ dysfunction and particular metabolizer or immunogenetic phenotypes, also appear to be important for development of the clinical syndromes identified as environmentally associated myopathies. Although data in this area are limited, they suggest that when susceptible individuals are exposed to selected agents, physiologic alterations occur that lead to myopathy. Physician awareness of chemicals implicated with myopathy and dissection of their pathogenetic mechanisms through human and animal studies may aid in the identification of additional toxic agents, minimize new cases in the future, and lead to a better understanding of the idiopathic myopathies.