Update in juvenile myositis

PURPOSE OF REVIEW: This update on childhood idiopathic inflammatory myopathies (IIMs) reviews recent progress in the field of translational science and clinical research over the past 12–18 months. RECENT FINDINGS: Several new studies, including results from the international genome-wide association study, point to abnormalities of the adaptive immune system in childhood IIMs. Circulating T-follicular helper cells promote plasma cell differentiation and have been found in high levels in juvenile dermatomyositis (JDM), which may account the frequency of autoantibodies seen in this disease. One of the latest to be identified in JDM targets the protein NXP-2 and is associated with an increased risk of calcinosis in young patients. The first randomized controlled clinical trial in refractory adult and childhood IIMs was reported this year. B-cell depletion with the anti-CD20 antibody, rituximab, failed to achieve its primary end point, but patients with JDM did show good improvement in disease activity. A new international definition of disease remission in JDM has been agreed, which will aid disease assessment in future therapeutic trials. SUMMARY: The challenges of studying a rare disease such as JDM have been overcome by several collaborative studies and have led to significant progress in understanding the cause, treatment and prognosis of childhood IIMs.