Dermatomyositis is an idiopathic inflammatory myopathy.
The role of the complement system in dermatomyositis pathogenesis is not fully understood.
Purpose of the Study:
To investigate the involvement of the complement system in dermatomyositis.
To determine if complement deposition occurs in the intramuscular microvasculature.
Main Methods:
Immunocytochemical studies using an antibody against the terminal C5b-9 membrane attack complex.
Analysis of muscle biopsy specimens from patients with childhood and adult dermatomyositis, polymyositis, and denervation atrophy.
Main Results:
The terminal C5b-9 membrane attack complex was found in the intramuscular microvasculature of 83% of childhood dermatomyositis patients and 26% of adult dermatomyositis patients.
No membrane attack complex deposition was observed in control specimens, including those with polymyositis and denervation atrophy.
Evidence of complement system deposition, binding, and activation within the intramuscular microvasculature.
Conclusions:
The complement system is activated within the intramuscular microvasculature in dermatomyositis.
These findings support the presence of vasculopathy in dermatomyositis.
Complement plays a primary role in mediating vessel injury, especially in childhood dermatomyositis.