Juvenile Dermatomyositis: New Clues to Diagnosis and Therapy

To identify clues to disease activity and discuss therapy options.

The diagnostic evaluation includes documenting symmetrical proximal muscle damage by exam and MRI, as well as elevated muscle enzymes-aldolase, creatine phosphokinase, LDH, and SGOT-which often normalize with a longer duration of untreated disease. Ultrasound identifies persistent, occult muscle inflammation. The myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) are associated with specific disease course variations. Anti-NXP-2 is found in younger children and is associated with calcinosis; anti-TIF-1γ+ juvenile dermatomyositis has a longer disease course. The diagnostic rash-involving the eyelids, hands, knees, face, and upper chest-is the most persistent symptom and is associated with microvascular compromise, reflected by loss of nailfold (periungual) end row capillaries. This loss is associated with decreased bioavailability of oral prednisone; the bioavailability of other orally administered medications should also be considered. At diagnosis, at least 3 days of intravenous methyl prednisolone may help control the HLA-restricted and type 1/2 interferon-driven inflammatory process. The requirement for avoidance of ultraviolet light exposure mandates vitamin D supplementation.

This often chronic illness targets the cardiovascular system; mortality has decreased from 30 to 1-2% with corticosteroids. New serological biomarkers indicate occult inflammation: ↑CXCL-10 predicts a longer disease course. Some biologic therapies appear promising.