clinical approach to muscle diseases

muscle diseases constitute a large variety of both acquired and hereditary disorders that can affect muscle structure, metabolism, or the function of the muscle channel. a successful clinical approach to a patient with a suspected myopathy is based on a thorough medical history and neurological examination. associated clinical symptoms such as myoglobinuria, contractures, myotonia, cardiac disease, and respiratory insufficiency can be extremely helpful in limiting the differential diagnosis. in addition, a phenotypic approach to diagnosis according to the patients predominant pattern of weakness is essential for guiding the physician in selecting the most appropriate diagnostic studies. although muscle biopsy remains a useful tool, molecular genetic studies are now available for the noninvasive diagnosis of many muscle diseases. muscle diseases are disorders in which there is a structural or functional abnormality of skeletal muscle. muscle diseases can be distinguished from other disorders of the motor unit (including motor neuron diseases, neuromuscular junction disorders, and peripheral neuropathies) by characteristic clinical and laboratory features. 1-the first goal, therefore, in approaching a patient with a suspected muscle disease is to identify the correct site of the lesion. 2-the second goal is to determine whether the muscle disease is due to an acquired or a hereditary disorder to provide accurate genetic counseling. 3-finally, the third goal in our clinical approach is to determine if there is a specific treatment. certainly in most hereditary muscle diseases, there is no curative therapy, and the clinicians focus must be on aggressive symptom management and the provision of appropriate adaptive equipment to maximize the patients functional abilities and enhance quality of life. despite the tremendous increase in the number and sophistication of diagnostic tests, the most important element of evaluating a patient with a suspected muscle disease remains a thorough history and physical examination. the findings on the physical examination, particularly the distribution of muscle weakness, should provide additional information in determining the correct diagnosis. many muscle diseases have features so characteristic that they can be diagnosed with relative certainty at the bedside. the results of laboratory studies, including creatin kinase, electrodiagnostic studies, muscle biopsy, and/or molecular genetic studies should play a confirmatory diagnostic role. although the basic components of the history are similar for patients with other medical conditions, certain features are unique to the patient with a suspected myopathy.