Juvenile-Onset Clinically Amyopathic Dermatomyositis

Juvenile-onset amyopathic dermatomyositis is an uncommon variant of juvenile-onset dermatomyositis (JDM), characterized by the hallmark cutaneous features of dermatomyositis for at least 6 months without clinical or laboratory evidence of muscle disease. Cutaneous calcinosis, vasculopathy, and interstitial lung disease frequently complicate the course of classic JDM (typical JDM with myositis) but are infrequent in amyopathic JDM. Recent literature suggests that approximately 75% of amyopathic JDM patients will remain free from muscle disease after years of follow-up, while approximately 25% of patients will evolve to having classic JDM. No clinical, laboratory, or ancillary parameters have been found to be predictive for this transition to muscle disease.

Treatment of the cutaneous disease of amyopathic JDM centers on photoprotection and topical therapies directed against inflammation. Oral antimalarials are effective for cutaneous disease not adequately controlled with topical care. Systemic corticosteroids, while central to the treatment of classic JDM, are controversial in the treatment of amyopathic JDM. Randomized controlled trials are not available to guide the management of this disease. Proponents for early aggressive systemic corticosteroid therapy for amyopathic JDM advocate that this intervention may decrease the likelihood of progression to classic JDM, and/or prevent disease-specific complications of JDM such as calcinosis. Opponents of early intervention with systemic corticosteroids favor expectant management directed toward controlling skin disease, citing the predictable adverse effects of systemic corticosteroids in the face of uncertain benefit. Other therapeutic options for severe and recalcitrant cutaneous disease, including methotrexate, intravenous immunoglobulin, and rituximab, are reviewed, as are treatment options for calcinosis cutis. In weighing the available evidence, the authors conclude that early aggressive treatment of amyopathic JDM with systemic immunosuppressant agents should be avoided in most cases as the risk of these medications will outweigh the measurable benefit. The reported literature suggests a good prognosis for amyopathic JDM. Ongoing clinical follow-up is recommended in all cases to allow early detection of subtle signs of muscle disease.