Anifrolumab for Refractory Juvenile Dermatomyositis: A Multicenter Pediatric Case Series

Objectives Refractory juvenile dermatomyositis (JDM) and idiopathic inflammatory myopathies pose significant therapeutic challenges, with a subset of patients failing to respond to the standard therapy of corticosteroids and immunosuppressants. Anifrolumab, a monoclonal antibody targeting the type I interferon receptor, has demonstrated effectiveness in treatment-resistant pediatric myositis, yet evidence is limited to a recent few case reports.[1] We aimed to detail the efficacy and safety of anifrolumab in treating 4 pediatric cases with refractory inflammatory myositis. Methods We retrospectively and prospectively reviewed the medical records of patients with childhood-onset inflammatory myositis who experienced persistent disease activity and were treated with anifrolumab. This study involved 2 tertiary medical centers: Hospital Sant Joan de Déu in Barcelona and the Hospital for Sick Children in Toronto. Data on demographics, disease manifestations and severity, laboratory findings, treatment details, and responses to therapy were collected. Results Four patients, 3 females and 1 male, aged 3.5 to 10 years at the time of diagnosis, were identified (Table 1). The median time from diagnosis to starting anifrolumab was 12 months (IQR 7.8 to 31). All presented with muscle weakness and cutaneous features, and patient 1 also had ulcerative skin disease, bowel perforation, and pulmonary infections. Patients 1 and 4 were positive for anti-NXP2 antibody, while patients 2 and 3 had positive anti-p155. Prior to commencing on anifrolumab infusions, all patients received prednisone, methylprednisolone pulses, and intravenous immunoglobulins (IVIG), along with 2 or more of methotrexate, tacrolimus, mycophenolate mofetil (MMF), and cyclophosphamide. Patient 1 also needed 3 surgeries due to bowel perforation. Clinical responses were evaluated after 6 anifrolumab infusions (5mg/kg q4 weeks) for patient 1, 3 infusions for patients 2 and 4, and 2 infusions for patient 3. All 4 patients demonstrated clinically meaningful improvement in their skin involvement and overall disease activity. Patient 4 experienced a halt in the progression of the calcinosis lesion, while patient 1 also saw significant improvement in muscle strength and no recurrence of gastrointestinal involvement. The prednisone dosage was substantially reduced in patients 2 and 3, while it was discontinued in case 1. No anifrolumab-related adverse effects were observed. Table 1: Demographics, Clinical Characteristics and Treatment History of Patients Conclusion This study highlights the promising efficacy of anifrolumab in the management of refractory JDM, with clinically meaningful improvement in cutaneous and other involvement, along with a favorable safety profile. These findings provide additional support for the systemic inhibition of type I interferon in managing the disease and emphasize the need for prospective studies. References [1.] Barrutia-Etxebarria A. Pediatr Dermatol 2026;43:116-20.