Developments in the classification and treatment of the juvenile idiopathic inflammatory myopathies

The juvenile idiopathic inflammatory myopathies(JIIM) are rare, heterogeneous autoimmune diseases that share chronic muscle inflammationand weakness. JIIM broadly includes three major clinicopathologic groups: juvenile dermatomyositis, juvenile polymyositis, and overlap myositis. A growing spectrum of clinicopathologic groups and serologic phenotypes defined by the presence of myositis-specific or myositis-associated autoantibodies are now recognized, each with differing demographics, clinical manifestations, laboratory findings, and prognoses. With the first multi-center collaborative studies and controlled trials using standardized preliminarily validated outcome measures, the therapy of juvenile myositishas advanced. Although daily oral corticosteroids remain the backbone of treatment, disease-modifying anti-rheumatic drugs (DMARDs) are almost always used as adjunctive therapy. Methotrexateis the conventional DMARD for the initial therapy, either alone or combined with intravenous pulse methylprednisolone, and/or intravenous immunoglobulin for patients with moderate to severe disease. Cyclosporine may be added to these or serve as an alternative to methotrexate. Other drugs and biologic therapies, including mycophenolatemofetil, tacrolimus, cyclophosphamide, rituximab, and infliximab, might benefit selected patients with recalcitrant disease, unacceptable steroid toxicity, or patients with risk factors for poor prognosis. The treatment of cutaneous disease, calcinosis, and the role for rehabilitation are also discussed.