Skeletal muscle immunopathology

The inflammatory myopathies are a heterogeneous group of diseases currently categorized by clinical findings, laboratory data, and routine histopathologic features. In the ten years since the direct immunofluorescent (DIF) findings in idiopathic inflammatory myopathy were described, there have been a variety of series reporting DIF findings in various rheumatic and non-rheumatic diseases. This paper reviews this experience and attempts to relate the observations to immunologic mechanisms applicable to skeletal muscle. The potential contributions of direct immunohistochemical methodologies have yet to be realized, because 1) there is a paucity of data actually correlating these findings to clinicopathologic data in patients and experimental models and 2) these techniques have been limited to probing for the humoral response. The future expanded use of this technique should include histochemically tagged antisera to T-lymphocyte antigens, macrophages, biologic modifiers, and suspected etiologic agents.