Background: Dermatomyositis (DM) presenting during childhood or adolescence classically encompasses hallmark cutaneous changes, proximal muscle weakness, and laboratory evidence of myositis. When cutaneous manifestations of DM are present without muscle weakness for > 6 months, the term 'clinically amyopathic DM' applies (syn. DM sine myositis).
Objectives: To review the clinical and epidemiological features of published cases of juvenile-onset clinically amyopathic DM, with comparison with adult-onset clinically amyopathic DM and juvenile-onset classical DM.
Methods: Systematic review of the published literature.
Results: We identified 68 cases of juvenile-onset clinically amyopathic DM published during 1963-2006. The disease in 18 of 68 (26%) patients subsequently evolved to classical DM. Overall, the mean age at diagnosis was 10.8 years (range 2-17) with nearly equal male/female ratio and mean follow-up of 3.9 years. Among cases with diagnostic testing, 10 of 19 had a positive antinuclear antibody titre, two of nine had elevated erythrocyte sedimentation rate and two of 51 had elevated creatine kinase (CK). Of patients with normal CK, three of 22 had abnormal electromyography, one of 19 had abnormal muscle biopsy, and one of nine had abnormal magnetic resonance imaging. Calcinosis was reported in three of 68. No cases of severe vasculopathy (resulting in ulceration), interstitial lung disease or internal malignancy were reported.
Conclusions: This review suggests a good prognosis for children with clinically amyopathic DM. A minority of patients with negative muscle enzymes had positive ancillary testing for myositis, and these patients rarely developed muscle weakness. Predictive factors for progression to classical DM were not identified. Symptomatic treatment of cutaneous involvement and close clinical monitoring may be an alternative to aggressive immunosuppression.