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Ultrastructural changes in polymyositis
Abstract:
Muscle biopsies from 32 cases with polymyositis and dermatomyositis were examined by electron microscopy. Most of the changes of the muscle fibres were non-specific and little structural difference was seen in the various clinical types. The muscle fibres sometimes showed rough endoplasmic reticulum, annulate lamellae and prominent Golgi apparatus. Thin and thick filamentous inclusions were present both in the sarcoplasm and nuclei of some muscle fibres. Thick filamentous inclusions were seen in chronic cases and were sometimes associated with annulate lamellae. Regeneration of muscle was often conspicuous. The endothelial cells of the blood vessels were hypertrophied; some cells contained granulotubular inclusions, rod-shaped bodies (Weibel-Palade bodies) and filamentous material. The basement membrane of the vessels was often multi-layered. The cells infiltrating the interstitial tissue included macrophages, lymphocytes, transformed lymphocytes, plasma cells, monocytes, mast cells and only occasional eosinophils and basophils. Lymphocytes, macrophages and a few plasma cells were seen between the plasma and basement membranes of degenerating muscle fibres. Changes were also noted in some intramuscular nerves, motor end-plates and a muscle spindle.
Insights
Electron microscopy revealed non-specific muscle fiber changes in polymyositis and dermatomyositis. Chronic cases showed thick filamentous inclusions, and vascular and inflammatory cell changes were prominent in these inflammatory myopathies.
Area of Science:
- Neurology
- Pathology
- Immunology
Background:
- Polymyositis and dermatomyositis are idiopathic inflammatory myopathies.
- Understanding the ultrastructural pathology is crucial for diagnosis and understanding disease mechanisms.
Purpose of the Study:
- To investigate the ultrastructural changes in muscle biopsies from patients with polymyositis and dermatomyositis using electron microscopy.
- To identify specific ultrastructural markers associated with disease type and chronicity.
Main Methods:
- Electron microscopy examination of muscle biopsies from 32 patients diagnosed with polymyositis or dermatomyositis.
- Detailed analysis of muscle fiber ultrastructure, vascular changes, and inflammatory cell infiltrates.
Main Results:
- Muscle fibers showed non-specific changes, with minimal structural differences between clinical types.
- Presence of rough endoplasmic reticulum, annulate lamellae, Golgi apparatus, and thin/thick filamentous inclusions in muscle fibers.
- Thick filamentous inclusions, often associated with annulate lamellae, were observed in chronic cases.
- Hypertrophied endothelial cells with inclusions, multi-layered basement membranes, and diverse inflammatory cell infiltrates (macrophages, lymphocytes, plasma cells) were noted.
- Changes were also observed in intramuscular nerves, motor end-plates, and muscle spindles.
Conclusions:
- Ultrastructural findings in polymyositis and dermatomyositis are largely non-specific but reveal characteristic inclusions in chronic stages.
- Significant vascular and inflammatory cell alterations contribute to the pathology of these inflammatory myopathies.
- Electron microscopy provides valuable insights into the complex cellular and subcellular changes occurring in the muscle tissue.