MRI-guided biopsy in inflammatory myopathy: initial results.

The purpose of this report is to describe our initial experience with techniques employing magnetic resonance imaging (MRI) to guide the choice of muscle to be biopsied in patients suspected of having inflammatory myopathy. Five patients with a clinical diagnosis of inflammatory myopathy (IM) were studied. Four were imaged prior to biopsy. Four had repeated examinations, either immediately following biopsy or to evaluate disease progression. Use of MRI to localize muscle lesions was associated with abnormal pathologic findings in all cases, including histopathologic demonstration of lymphocyte infiltration in three cases of idiopathic polymyositis; nonspecific myopathic changes were seen in one patient with probable dermatomyositis and in one patient with chronic inflammatory polyneuropathy and high serum creatine kinase levels (> 45,000 IU/ml). The precise location of the area sampled by biopsy was visible in only one of four postbiopsy images. MRI shows promise in identifying pathologic muscle in patients suspected of having one of the inflammatory myopathies; however, further refinement of localization techniques may be needed to optimize histopathologic diagnoses.