Cutaneous Features

Dermatomyositis has several classic cutaneous findings (Figure 27-1). Gottron’s papules are erythematous, raised, scaling plaques on the dorsal surface of the knuckles, elbows, and knees that are present in more than 90% of children at the time of diagnosis. Gottron’s papules are frequently confused with severe eczema if JDMS is not suspected. The classic heliotrope rash is a violaceous discoloration of the eyelids with associated eyelid edema; this is present in approximately 80% of children at diagnosis. About 40% of children also have a prominent erythematous malar rash. This rash can be ulcerative, cross the nasolabial folds, and extend onto the forehead. Raynaud’s phenomenon (Figure 27-2) and associated nailfold capillary changes are seen in up to 80% of patients. Nailfold changes are characterized by proximal nailfold erythema, capillary dilatation, tortuosity, or dropout. The measured density of capillaries per millimeter may be a useful tool for monitoring clinical activity. Skin ulcerations reflect significant vasculopathy of the skin and may be a sign of internal organ vasculopathy. Ulcerative skin lesions are associated with more severe disease and worse prognosis.

Figure 27-1 Cutaneous findings of juvenile dermatomyositis.

Figure 27-2 Raynaud’s phenomenon in juvenile dermatomyositis.

Calcinosis, or calcium deposition in the skin and subcutaneous tissues, occurs in up to 40% of patients within a few years of diagnosis. Risk factors for the development of calcinosis include delayed diagnosis or treatment, TNF-α-308a genotype, and an age younger than 5 years at the time of diagnosis. Calcinosis may regress after disease remission, but complete resolution may take years. The calcinosis associated with JDMS occurs in five distinct patterns: (1) superficial calcinosis on the extremities that does not interfere with function and often regresses spontaneously; (2) deep tumoral muscle calcification in the proximal muscle groups that may interfere with joint motion, may ulcerate, and may require surgical debridement; (3) diffuse and painful calcinosis along myofascial planes that limits joint motion; (4) mixed forms of the former three types; and (5) extensive exoskeleton-like calcium deposits that result in severe functional limitations.

Other less common skin manifestations associated with JDMS are “mechanics’ hands” (thickening of the margins of the palms and radial surfaces of the hands), the shawl sign (macular erythema on the posterior neck and shoulders), the V sign (macular erythema on the anterior neck and chest), and poikiloderma vasculare atrophicans (circumscribed violaceous erythema with associated telangiectasia, hypopigmentation or hyperpigmentation, and superficial atrophy). The scalp may also be involved with seborrhea-like scaling, atrophy, and alopecia. Lipodystrophy is often underappreciated and may be present in 20% to 50% of children; it may be associated with insulin resistance, decreased glucose tolerance, acanthosis nigricans, and elevated triglycerides.

Musculoskeletal Features

Classic JDMS is manifested by symmetric, proximal muscle weakness especially in the neck, hip flexors, and abdominal wall (Figure 27-3). Targeted muscle testing is necessary because children are often able to compensate well for their weaknesses. Children may have functional limitations at the time of presentation secondary to muscle involvement. For example, affected children may report problems with brushing or washing their hair, climbing stairs, and standing from a seated position (Gower’s sign). Dysphonia, difficulty swallowing, dysphagia, and reflux of food into the nasopharynx may be present due to weakness of the palate, cricopharyngeal muscles, and upper esophagus. Rarely, the myocardium can be involved. Joint contractures may be present as a result of muscle shortening. Muscle tenderness may also be a prominent feature.

Figure 27-3 Proximal muscle weakness in juvenile dermatomyositis.

Amyopathic JDMS has the cutaneous manifestations of JDMS in the absence of clinically apparent muscle disease. Often, imaging by magnetic resonance imaging (MRI) and detailed muscle testing reveals subtle subclinical disease in these cases.

Other Disease Manifestations

Pulmonary involvement is less common in children than adults and is associated with the presence of anti-Jo-1 antibody. Interstitial lung disease and spontaneous pneumothorax may rarely occur. Gastrointestinal vasculopathy is also a rare, but life-threatening, complication that can cause multiple perforations of the gastrointestinal tract. Involvement of the central nervous system may be manifested by edema, seizures, and hallucinations. Anasarca is a poor prognostic sign indicating severe disease that may respond very slowly to treatment and may not respond to corticosteroids alone.