Amyopathic dermatomyositis associated with malignancy

A 77-year-old woman presented with a photosensitive macular eruption, poikiloderma, diffuse alopecia, and a heliotrope eruption (Fig. 1), along with periungual telangiectasias (Fig. 2), Gottron's papules, and Gottron's sign. She had no evidence of muscle weakness, calcinosis, sclerodactyly, or synovitis. Laboratory studies revealed: creatine phosphokinase (CK) 27 U/L (Normal: 0-170), aldolase 4.0 U/L (0-6), positive antinuclear antibody (ANA) (titer 1:640, speckled), negative double-stranded DNA, negative other autoantibodies (including SSA, SSB, Smith, RNP, and Jo-1), normal complement levels, C-reactive protein < 1.0 mg/L (0-8), Westergren erythrocyte sedimentation rate 19 mm/per hour (0-20), normal complete blood count and thyroid function tests. Despite the high-titer ANA and the photosensitive eruption, no other clinical or laboratory manifestations of systemic lupus erythematosus were present. A punch biopsy from sun-exposed lesional skin was consistent with dermatomyositis (DM), showing a thinned epidermis with hydropic degeneration of the basal cell layer and pigmentary incontinence. The upper dermis was edematous and there was a perivascular lymphocytic infiltrate and extensive dermal mucin deposition. Direct immunofluorescence testing revealed IgM positivity on colloid bodies; IgG, IgA, C3, and fibrin were negative. Initial electromyographic (EMG) and magnetic resonance imaging (MRI) studies of proximal muscle groups were normal. Sequential muscle evaluation, including strength-testing, serum enzyme levels, and EMG, has remained normal over the past 2 years. Initial screening for malignancy that included chest roentgenogram, mammography, and gynecologic evaluation, was negative. In addition, flexible sigmoidoscopy to the splenic flexure was normal. One year after the onset of her skin lesions, she developed an enlarged inguinal lymph node that revealed adenocarcinoma on biopsy. Subsequent evaluation identified a region of the colon that had been previously visualized by endoscopy as the primary tumor site. She is currently undergoing therapy for her malignancy and, while her eruption remains unchanged, remains amyopathic.