A 44-year-old woman presented with 6 month history of muscle pain in her thighs, arms, forearms, and shoulders associated with weakness, and a macular rash on her upper and lower extremities. She recalled a weight loss of 30 lb (13.5 kg), fever, and decreased appetite. Physical examination revealed macular erythematous patches over the dorsal surface of the hands (fig 1A), especially over the metacarpophalangeal and proximal interphalangeal joints, knees (fig 1B), elbows (fig 1C), toes with dystrophic cuticles (fig 1D), and medial malleoli. She also experienced muscle pain upon palpation of her thighs, arms and shoulders. Blood tests showed elevated creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase concentrations.

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Figure 1

Macular erythematous patches (Gottron’s papules) over the dorsal surface of the hands (A), especially over the metacarpophalangeal and proximal interphalangeal joints, knees (B), elbows (C), and toes with dystrophic cuticles (D).

The most probable diagnosis is dermatomyositis, which is identified by a characteristic rash accompanying muscle weakness. Characteristic is the Gottron rash (fig 1), a raised violaceous rash or papules at the knuckles, which is prominent in metacarpophalangeal and interphalangeal joints.1^,2 Others skin manifestations include a heliotrope rash (blue-purple discoloration) on the upper eyelids, in many cases associated with oedema, and an erythematous rash on the face, neck, and anterior chest (in many patients in the shape of a V sign), or on the back and shoulders (shawl sign), knees, elbows, and malleoli; the rash can be exacerbated after exposure to the sun and is pruritic in some cases.2 The lateral and palmar areas of the fingers may become rough with cracked, “dirty” horizontal lines, resembling “mechanics’ hands”.

Dermatomyositis can be associated with cancer. There is a threefold increase in the risk of malignant disease following diagnosis of dermatomyositis. The most common cancers are those of the ovaries, gastrointestinal tract, lung, breast, and non-Hodgkin lymphomas.3 The risks of ovarian, pancreatic, and lung cancer remain high up to 5 years after diagnosis of dermatomyositis, and the increased risk of pancreatic and colorectal cancer extend past the 5 year follow-up period.3

Treatment is based on immunosuppressive agents, including high dose corticosteroids, azathioprine or methotrexate (combined from the outset or added later), intravenous immunoglobulin (IVIg), and the use of mycophenolate, cyclosporin or cyclophosphamide.4