Juvenile dermatomyositis (jDM) is the most common idiopathic inflammatory myopathy of childhood [
1]. This systemic autoimmune disease is associated with typical changes in the skin, vasculopathy, and muscle weakness that is usually trunk accentuated [
2]. The exact etiology of jDM is still unclear. It is discussed that based on a genetic predisposition, external environmental factors trigger an autoimmune response [
3]. In the pathogenesis of vasculopathy in jDM, activation of type I interferon-induced genes seems to play an important role [
4,
5]. In 60–90% of patients with jDM, myositis-specific antibodies, such as anti-TIF 1-γ (p155), anti-NXP2/(p140/MJ), anti-MDA5, as well as myositis-associated antibodies, such as anti-La (‘SSB’), anti-Ro (‘SSA’), and anti-Sm, can be detected and helpful in establishing the diagnosis [
6,
7].
Melanoma differentiation-associated protein 5 (MDA5) is physiologically involved as a pattern recognition receptor in the recognition of viral nucleic acid sequences. Here, the ongoing signaling cascade leads to activation of the type I interferon response [
8,
9]. It has been shown that different autoantibodies are associated with different clinical phenotypes. MDA5 autoantibodies are associated with an increased risk of skin ulceration, arthritis, interstitial lung disease (ILD), as well as an amyopathic or hypomyopathic course in jDM [
6]. Sontheimer et al. define hypomyopathic dermatomyositis as “dermatomyositis-specific skin disease and no clinical evidence of muscle disease (i.e., weakness) that are found to have subclinical evidence of myositis upon laboratory, electrophysiological and/or radiological evaluation” [
10]. A review from 2022 [
11] reported that up to 80% of patients with clinically amyopathic dermatomyositis can develop ILD. If MDA5 autoantibodies are present, the association with ILD is even higher (up to 95%). The ILD in MDA5 autoantibody positive jDM is critical due to its treatment refractory course and high mortality rates (6-month mortality up to 50%). Therapy of jDM is based on the administration of glucocorticoids, intravenous immunoglobulins (IVIG), and cDMARDs (such as methotrexate, mycophenolate mofetil, and azathioprine). In severe courses or refractory disease, drugs such as rituximab, TNF-alpha inhibitors, or cyclophosphamide are used [
1,
12,
13]. Given the crucial role of the JAK STAT pathway in the pathophysiology of the disease, JAK inhibitors represent a reasonable therapeutic option in jDM. Several case reports describe a positive effect of JAK inhibition (ruxolitinib, tofacitinib, baricitinib) in refractory jDM [
14‐
16].