Is it really an inflammatory myopathy? Value of immunohistochemistry of muscle tissue in the differential diagnosis of myositis

Overview

The correct diagnosis of idiopathic inflammatory myopathies is of importance with respect to the available treatment. On the other hand, the potentially toxic immunosuppressive treatment of a patient suffering by other than inflammatory myopathy may result in undesired affection of the patient’s health. It is increasingly recognized that there exist both the clinical and the muscle histopathologic overlap between the features of inflammatory myopathies and some of the hereditary muscular dystrophies. Recent progress in understanding the pathogenesis of many myodystrophies included in the differential diagnosis of inflammatory myopathies led to the development of new strategies in muscle biopsy analysis. In the current report, the available methods in diagnostic myopathology are presented, the value of immunohistochemistry in the differential diagnosis between inflammatory myopathies and myodystrophies is exemplified by three case reports (manifest carrier of a dystrophinopathy, calpainopathy and merosindeficient congenital myodystrophy) and followed by the discussion. A review of the diagnosis should always be considered in cases with atypical presentation of an inflammatory myopathy as well as in cases lacking the specific response to the immunotherapy.

Key words:
myositis, inflammatory myopathy, muscular dystrophy, immunohistochemistry