Juvenile idiopathic inflammatory myopathy : A muscle pathology perspective.

Abstract

Autoimmune myositis had been classified into dermatomyositis and polymyositis based mainly upon the presence or absence of skin rash. However, recent advances in muscle pathology and serology have revealed the presence of at least three independent subtypes in juvenile autoimmune myositis : dermatomyositis, immune-mediated necrotizing myopathy, and antisynthetase syndrome, each of which has distinct pathogenesis while the existence of pathologically-defined polymyositis has become questionable. Most of the pediatric patients who are clinically diagnosed with polymyositis actually have either immune-mediated necrotizing myopathy, antisynthetase syndrome, or dermatomyositis sine dermatitis.