Pathophysiology
Polymyositis is believed to be an autoimmune disorder, where the body's immune system mistakenly attacks its own muscle tissues. The
pathophysiological mechanisms involve the presentation of muscle antigens by
major histocompatibility complex (MHC) class I molecules to CD8+ T cells, leading to cytotoxic damage.
Diagnostic Techniques
Histological examination remains a cornerstone for diagnosing polymyositis. A muscle biopsy is typically performed, and the tissue is stained using
hematoxylin and eosin (H&E) to visualize the inflammatory infiltrates and muscle fiber damage. Immunohistochemical staining is also used to identify specific cell types and molecules involved in the inflammatory process.
Differential Diagnosis
Distinguishing polymyositis from other inflammatory myopathies is crucial for proper treatment. For instance,
dermatomyositis often shows perivascular and perimysial inflammatory infiltrates, whereas polymyositis primarily involves endomysial inflammation. Inclusion body myositis, on the other hand, is characterized by the presence of
rimmed vacuoles within muscle fibers.
Treatment and Prognosis
Treatment of polymyositis typically involves immunosuppressive therapies, such as
corticosteroids,
methotrexate, and
azathioprine. The prognosis varies among patients, with some responding well to treatment and others experiencing a more chronic, debilitating course.
Conclusion
Polymyositis is a complex disorder with distinctive histological features that aid in its diagnosis and differentiation from other myopathies. Understanding the histological characteristics and underlying pathophysiological mechanisms is crucial for effective management and treatment of this condition.
