RESUMO
Muscle diseases are an expanding field, mainly due to the progress in genetics and biochemistry. Evaluation starts with a thorough history of the patient's symptoms and signs. The leading clinical manifestations are weakness, atrophy, myalgia, fatigue, more rarely myotonia and in the child hypotonia or walking difficulty. A detailed family history might give clues to an underlying genetic etiology. Diagnostic workup begins with the measurement of serum creatine kinase. Electroneuromyography is an important investigation procedure which includes motor and sensory nerve conduction studies and concentric needle electromyography. Muscle biopsy is performed in all patients with clinical evidence of myopathy. A fine-needle technique is generally used, more often than a surgical biopsy. Molecular analysis of candidate genes is becoming a major diagnostic tool in many muscle disorders. Muscle imaging, in particular MR, provides diagnostic and follow-up information, especially in dystrophic, metabolic and inflammatory myopathies. Exercise testing can be useful in some metabolic myopathies. There is no standard protocol for the choice and course of investigations which must always be based on a detailed clinical evaluation. It is important to establish a precise diagnosis in order to inform the patient about the nature and the evolution of the disease, the therapeutic options and to propose, when indicated, genetic counseling.