Novel use of anifrolumab in a young patient with Jo-1-positive juvenile dermatomyositis

Refractory Jo-1-positive juvenile dermatomyositis with calcinosis cutis shows favourable response to anifrolumab. Dear Editor, Anifrolumab is a monoclonal antibody targeting subunit 1 of the type 1 interferon (IFN) receptor. Experience with anifrolumab in patients with JDM is limited to predominantly adult or adolescent patients treated with a higher dose (300 mg/month) for skin and muscle disease, without calcinosis cutis and without longitudinal IFN signature assessments reported [1–3]. Two patients with anti-transcription intermediary factor 1γ–positive JDM and rapid response to anifrolumab were published in June 2025 [4]. Anifrolumab is currently approved for the treatment of SLE in adults and a study of anifrolumab in paediatric SLE is currently under way. This case report describes the changes in disease activity and expression of type 1 IFN-stimulated genes in whole blood over 7 months with off-label use of anifrolumab (150 mg/month) in an 8-year-old girl with refractory skin involvement combined with severe calcinosis cutis. Jo-1-positive JDM was first diagnosed at the age of 4 years, with Gottron’s papules, skin erythema (Fig. 1C) and MRI-confirmed myositis present. The initial treatment included methylprednisolone pulse therapy, oral prednisolone and methotrexate. Six months later, hydroxychloroquine was added. The treatment was ineffective, leading to an increased oral prednisolone dose after 12 months of therapy. Off-label tofacitinib, initiated 16 months after diagnosis, with a starting dose of 3.75 mg twice daily, followed by an increase to 4 mg twice daily after 14 months of treatment, significantly improved myositis [Childhood Myositis Assessment Scale (CMAS): 37–51 (maximum 52)] and the 20-item DAS [DAS20: 15 to 9 (worst 20)]. Minimal change in the IFN signature (median of the whole blood expression of six type 1 IFN-stimulated genes measured by real-time PCR: IFI27, IFI44L, IFIT1, ISG15, RSAD2, SIGLEC1; normal