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Necrotizing myopathy with microvascular deposition of the complement membrane attack complex.
J De Bleecker1, V Vervaet, P Van den Bergh
1Department of Neurology, Ghent University Hospital, Ghent, Belgium. jan.debleecker@Ugent.be
Clinical Neuropathology
|April 13, 2004
Summary
Necrotizing myopathy, often lacking inflammation, is a recognized autoimmune condition. Muscle biopsies showing microangiopathy and MHC class I expression can indicate treatable myopathy, even without overt inflammation.
Area of Science:
- Neurology
- Immunology
- Pathology
Background:
- Necrotizing myopathy without significant inflammation is an emerging diagnostic category within inflammatory myopathies.
- It is distinct from established conditions like dermatomyositis, polymyositis, and sporadic inclusion-body myositis.
Observation:
- A case study of a patient with chronic, steroid-responsive myopathy and an overlap syndrome is presented.
- Muscle biopsy revealed thickened small blood vessels (capillaries and arterioles) with membrane attack complex deposition.
- Muscle fibers exhibited widespread major histocompatibility class I (MHC I) expression.
Findings:
- The observed microangiopathy and MHC I expression in muscle fibers suggest an autoimmune process.
- These findings occurred in a patient with an undifferentiated connective tissue disorder and a history of carcinoma, though the link remains unclear.
Implications:
- The study highlights that a lack of prominent inflammation on muscle biopsy does not rule out treatable autoimmune inflammatory myopathy.
- It underscores the importance of considering microvascular changes and MHC I expression in diagnosing atypical myopathies.