Skin lesions of dermatomyositis (DM) are often pruritic. The characteristic lesions are the heliotrope rash and Gottron’s papules. The heliotrope rash consists of a periorbital violaceous to dusky erythematous rash, which may be edematous (Fig. 14-1). Gottron’s papules are erythematosus to violaceous papules or plaques found over bony prominences, particularly over the metacarpophalangeal joints, the proximal interphalangeal joints, and the distal interphalangeal joints (Fig. 14-2). Nail-fold changes consist of periungual telangiectasias and cuticular hypertrophy with small hemorrhagic infarcts. Patches of poikiloderma—mottled, atrophic, and telangiectatic skin—develop on exposed surfaces, such as the extensor arm and the anterior V of the neck. The scalp may be red and intensely pruritic with diffuse scale and alopecia. Calcinosis of the skin or muscle is unusual in adults but may occur in up to 40% of children with DM, particularly those who are not treated aggressively with corticosteroids and/or immunosuppressive agents.

More than 90% of patients with skin lesions eventually have myopathy, but the skin lesions may precede muscle disease by months to years. There are a small group of patients who never develop weakness and in whom repeated muscle enzyme testing is normal; these patients are said to have amyopathic DM. The myopathy of DM mainly affects the proximal muscle groups of
the shoulder and pelvic girdles and is usually symmetric. Initial complaints include weakness, fatigue, inability to climb stairs and raise the arms for hair grooming or shaving, and weakness in rising from a squatting or sitting position. Arthralgias or arthritis occur in up to 25% of patients. Dysphagia is present in 20% to 50% and can be either proximal or distal. Approximately 20% of patients with DM have an associated malignancy regardless of whether or not they have myositis. Malignancy usually appears within the first 3 years following diagnosis.