Clinical features of juvenile dermatomyositis
epidemiology and clinical manifestations of a child presenting with juvenile dermatomyositis (JDM)
JDM is an immune-mediated vasculitis that presents with an inflammatory myositis and a characteristic skin rash. The mean age of onset is 6 to 9 years, with 25% occurring in children aged <4 years. In whites, it is associated with human leukocyte antigen-DRB1∗0301. Muscle weakness, in particular of the proximal musculature (limbs, girdle, neck), is prominent (80%–100% of patients). The Gower maneuver is abnormal, and the child will be unable to do a sit-up as a result of weakness. The head may hang back as the child is lifted from a lying position, owing to weakness of the neck flexors. Skin manifestations are characteristic. The eyelids and face are edematous, and a heliotrope or mauvish rash is noted around the eyes (75%). Deep red patches (66%–95%), known as Gottron papules, are seen over the extensor surfaces of the finger joints, as well as over the elbows, knees, and ankle joints. These patches may ulcerate as a result of vasculitis. Telangiectasias may be found around the eyelids, and capillary dilatation and dropout can be found around nailfolds and gum margins . GI manifestations include dysphagia (18%–44%) and intestinal vasculitis causing abdominal pain, lower GI bleeding, and bowel perforation. Arthralgia or arthritis may occur (20%–60%), sometimes with swelling and contractures of the fingers resulting from tenosynovitis. The most common lung finding is a decreased carbon monoxide diffusing capacity in 50% of patients. Cardiac involvement is uncommon. Treatment of JDM with the combination of GCs plus another immunosuppressive (e.g., methotrexate) is more effective than GCs alone.
