To describe the clinical and muscle pathological characters of juvenile myositis patients with perifascicular atrophy (PFA).

A series of 21 consecutive muscle biopsies with clinically and pathologically confirmed juvenile myositis were studied. All biopsies had PFA of muscle fibers.

Clinical manifestation: 11/21 had typical dermatomyositis rash, 9/21 possible dermatomyositis because of atypical rash, 1/21 mixed connective tissue disease; 9/21 had weakness complaint; 9/21with normal creatine kinase (CK) level, 4/21 low grade rise, 8/21 apparently elevated, 10/11 definite dermatomyositis patients with normal or low grade level; 6/21 combined with interstitial lung disease, 2 with EB virus infection, 1 with cytomegalo virus infection. Muscle pathology: 4 specimens with atypical PFA also had enzyme abnormality in nicotinamide adenine dinucleotide, succinate dehydrogenase and cytochrome c oxidase staining, 9/12 cases had membrane attack complement deposition intramuscular capillaries, and they had prominent regional mitochondrial abnormalities, protrude PFA and focal muscle damage. Skin biopsy of one case showed perivasculitis in dermis.

PFA could be seen in juvenile dermatomyositis and mixed connective tissue disease, and PFA could not increase the CK level. The capillary and intermediate-sized vessels damage may cause chronic ischemia, which could explain the PFA with mitochondrial abnormalities.

Dermatomyositis; Muscular atrophy; Complement membrane attack; Mitochondria; Biopsy