Objective: To analyze the average age, sex distribution, duration of follow-up, clinical course, serologic abnormalities, and incidence of possibly associated malignancy in patients with amyopathic dermatomyositis.
Design: Retrospective study.
Setting: University hospitals.
Patients: Thirteen patients with amyopathic dermatomyositis.
Results: The 13 patients represented 8.2% of 157 patients with dermatomyositis seen retrospectively in a 10-year period by the Italian Group of Immunodermatology of the Italian Society of Dermatology and Venereology. Gottron papules and sign and periungual telangiectasias were found in approximately 50% of cases (papules in 7 patients, Gottron sign and periungual telangiectasias in 6), while periorbital violaceous erythema was seen in 70% (9 patients). Arthralgias occurred in 2 patients and Raynaud phenomenon in 4. An elevated erythrocyte sedimentation rate was detected in 6 patients, hepatitis B virus antigen in 3, speckled antinuclear antibodies in 7, and anti-Ro and antimitochondrial antibodies in 1 case each. None of our patients had evidence of internal malignancy. Neither cardiopulmonary nor esophageal dysfunction was demonstrated. Electromyography showed a protopathic muscle abnormality in 3 patients. Muscle biopsy disclosed myositis and a neurogenic myopathy in another one.
Conclusions: Amyopathic dermatomyositis is a rare disease. So far, only 2 series of a few cases each have been reported. The "amyopathic" subset of dermatomyositis is peculiar in that its cutaneous lesions are predominant for long periods or even permanently, although they are indistinguishable from those of classic dermatomyositis. The minimal or absent muscle disease and the rarity of serum immunologic findings imply a favorable prognosis in white patients.