[Drug-induced and toxic myopathies].

A large number of drugs and toxins may induce myopathic changes in several ways, they are probably more common than realized. The clinical and pathological features depend on the causative agent and on individual susceptibility to a given compound. Based on their pathologic mechanisms, there are 6 main categories of toxic myopathies: necrotizing myopathy mainly due to lipid-lowering drugs (fibrates and statines); vacuolar myopathy, usually associated with antimalarial agents; inflammatory myopathy induced by thiol derivatives; mitochondrial myopathy; steroid myopathy, and hypokaliemic myopathy. Toxic myopathies are usually reversible after discontinuation of the offending agent. Their prompt recognition may reduce their damaging effects or prevent a fatal outcome. Muscle biopsy can be very useful for the diagnosis of toxic myopathies.