In clinic, a 14 year-old female is seen for erythematous plaques over her knuckles, elbows, and knees. She also has a purplish rash on her eyelids and some erythema on her cheeks. When you ask her to stand up so you can examine her back, she has trouble getting up out of the chair.

What are the differences between the juvenile and adult forms of dermatomyositis?

In children, the differential diagnosis of a chronic inflammatory myopathy is much smaller than that seen in adults as polymyositis (2 - 8% of childhood idiopathic inflammatory myopathy) is much rarer than juvenile dermatomyositis (JDM) and inclusion body myositis and malignancy-associated myositis are exceedingly rare. Children with JDM are more likely than adults with DM to get calcinosis, lipodystrophy, and gastrointestinal and cutaneous ulcerations. Children with JDM get anti-synthetase antibodies 0 - 5% of the time, compared to 20 - 25% of adult patients.

What should you be worried about if a patient with JDM presents with acute onset of abdominal pain?

A small percentage of children with JDM may develop visceral vasculopathy which may lead to death. Severe abdominal pain, with or without melena or hematemesis, may signify vasculopathy of the gastrointestinal tract and resulting tissue ischemia or mesenteric infarction. The presence of cutaneous ulceration signifies a patient who is at higher risk for visceral ulceration and may warrant more aggressive therapy with cytotoxic agents.