Rapid and sustained response to JAK inhibition in a child with severe MDA5 + juvenile dermatomyositis

Background Juvenile dermatomyositis (jDM) is the most common idiopathic inflammatory myopathy of childhood. Amyopathic or hypomyopathic courses have been described. Case presentation We present the case of a 4-year-old patient with MDA5 antibody positive jDM and interstitial lung disease. In our patient, typical symptoms of jDM with classical skin lesions, arthritis, proximal muscle weakness, and ulcerative calcifications were observed. Due to the severity of the disease and the pulmonary changes, therapy with the Janus kinase (JAK) inhibitor ruxolitinib was added to the therapy with corticosteroids, intravenous immunoglobulins (IVIG) and hydroxychloroquine leading to a fast and sustained remission. Conclusion While there is growing evidence that JAK inhibition is a promising therapeutic option in jDM our case report shows that this approach may also be effective in MDA5-positive jDM with high risk features.