Chapter 055. Immunologically Mediated Skin Diseases (Part 7)

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Dermatomyositis The cutaneous manifestations of dermatomyositis (Chap. 383) are often distinctive but at times may resemble those of systemic lupus erythematosus (SLE) (Chap. 313), scleroderma (Chap. 316), or other overlapping connective tissue diseases (Chap. 316). The extent and severity of cutaneous disease may or may not correlate with the extent and severity of the myositis. The cutaneous manifestations of dermatomyositis are similar whether the disease appears in children or the elderly, except that calcification of subcutaneous tissue is a common late sequela in childhood dermatomyositis. The cutaneous signs of dermatomyositis may precede or follow the development of myositis by weeks...

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Chapter 055. Immunologically Mediated Skin Diseases (Part 7) Dermatomyositis The cutaneous manifestations of dermatomyositis (Chap. 383) are often distinctive but at times may resemble those of systemic lupus erythematosus (SLE) (Chap. 313), scleroderma (Chap. 316), or other overlapping connective tissue diseases (Chap. 316). The extent and severity of cutaneous disease may or may not correlate with the extent and severity of the myositis. The cutaneous manifestations of dermatomyositis are similar whether the disease appears in children or the elderly, except that calcification of subcutaneous tissue is a common late sequela in childhood dermatomyositis.
The cutaneous signs of dermatomyositis may precede or follow the development of myositis by weeks to years. Cases lacking muscle involvement (i.e., dermatomyositis sine myositis) have also been reported. The most common manifestation is a purple-red discoloration of the upper eyelids, sometimes associated with scaling ("heliotrope" erythema; Fig. 55-3) and periorbital edema. Erythema on the cheeks and nose in a "butterfly" distribution may resemble the malar eruption of SLE. Erythematous or violaceous scaling patches are common on the upper anterior chest, posterior neck, scalp, and the extensor surfaces of the arms, legs, and hands. Erythema and scaling may be particularly prominent over the elbows, knees, and the dorsal interphalangeal joints. Approximately one-third of patients have violaceous, flat-topped papules over the dorsal interphalangeal joints that are pathognomonic of dermatomyositis (Gottron's sign or Gottron's papules; Fig. 55-4). These lesions can be contrasted with the erythema and scaling on the dorsum of the fingers in some patients with SLE, which spares the skin over the interphalangeal joints. Periungual telangiectasia may be prominent. Lacy or reticulated erythema may be associated with fine scaling on the extensor surfaces of the thighs and upper arms. Other patients, particularly those with long-standing disease, develop areas of hypopigmentation, hyperpigmentation, mild atrophy, and telangiectasia known as poikiloderma. Poikiloderma is rare in both SLE and scleroderma and thus can serve as a clinical sign that distinguishes dermatomyositis from these two diseases. Cutaneous changes may be similar in scleroderma and dermatomyositis and may include thickening and binding down
of the skin of the hands (sclerodactyly) as well as Raynaud's phenomenon. However, the presence of severe muscle disease, Gottron's papules, heliotrope erythema, and poikiloderma serve to distinguish patients with dermatomyositis. Skin biopsy of erythematous, scaling lesions of dermatomyositis may reveal only mild nonspecific inflammation but sometimes may show changes indistinguishable from those found in SLE, including epidermal atrophy, hydropic degeneration of basal keratinocytes, edema of the upper dermis, and a mild mononuclear cell infiltrate. Direct immunofluorescence microscopy of lesional skin is usually negative, although granular deposits of immunoglobulin(s) and complement in the epidermal basement membrane zone have been described in some patients. Treatment should be directed at the systemic disease. Topical glucocorticoids are sometimes useful; patients should avoid exposure to ultraviolet irradiation and use photoprotective measures such as broad-spectrum sunscreens. Figure 55-3
Dermatomyositis. Periorbital violaceous erythema characterizes the classic heliotrope rash. (Courtesy of James Krell, MD.) Figure 55-4
Gottron's sign. Dermatomyositis often involves the hands as erythematous flat-topped papules over the knuckles (Gottron's sign). Periungual telangiectases are also evident.[newpage]