[Diagnostic principles in myopathies].
Myopathies include a broad range of disorders. Diagnostic steps in muscle disorders should therefore be followed sequentially, in order not to miss important information and to avoid unnecessary and cost intensive diagnostic procedures. Specific care should be applied in taking patient's history to ascertain myopathy related complaints, triggers and concomitant diseases possibly being accompanied by a myopathy. Clinical examination may reveal a distribution pattern already suggestive for a specific disorder. An elevated creatine kinase, often leading to neurological evaluation, should at least be repeated once after resting. Metabolic myopathies might be detected by exercise testing. Electromyography, muscle imaging and, usually as the last diagnostic step, muscle biopsy represent further diagnostic tools in the assessment of myopathies. In some disorders molecular genetic techniques can be applied.