• (1) Age ≥ 5 years old;

• (2) Diagnosis of juvenile dermatomyositis (JDM) according to Bohan and Peter criteria;

• (3) Meeting the classification criteria for RJDM, and meeting condition ① and any one of ② to ⑤ conditions:

⁃ Intolerance or inadequate response to glucocorticoids (prednisone 1-2mg/kg/d or equivalent dose of other hormones) and at least two immunosuppressants, with hormone therapy lasting for at least 6 months;

‣ Rapid progression of the disease and/or involvement of organs such as lungs, heart, and gastrointestinal tract;

∙ Calcification of subcutaneous or muscular and articular tissues;

• Repeated skin rashes or ulcers;

⁃ Repeated or persistent muscle weakness (muscle magnetic resonance imaging indicating widespread, diffuse edema or a Children's Myositis Assessment Scale (CMAS) score \< 48, and at least two abnormal results among the following five core measurement indicators: Physician's Global Assessment (PhGA) ≥ 2cm, Patient's Global Assessment (PtGA) ≥ 2cm, Disease Activity Score (DAS) ≥ 2 points, Child Health Assessment Questionnaire (C-HAQ) total score ≥ 0.25 points, and muscle enzyme level \> 1.5 times the upper limit of normal (ULN));

• (4)Patients with immune-mediated necrotizing myopathy who are positive for SRP or HMGCR antibodies meet the criteria for RJDM and can be directly included;

• (5) Basic normal function of important organs:

⁃ Cardiac function: Left ventricular ejection fraction (LVEF) ≥55%, with no significant abnormalities observed in the electrocardiogram;

‣ Renal function: eGFR ≥ 30mL/min/1.73m2;

∙ Liver function: AST and ALT ≤3.0 ULN, total bilirubin ≤2.0×ULN (excluding those caused by primary diseases);

• Pulmonary function: SpO2 ≥92%;

• (6) Female subjects of childbearing age have a negative result in the urine pregnancy test and agree to take effective contraceptive measures during the trial until one year after infusion;

• (7) The patient or their guardian agrees to participate in this clinical trial and signs an informed consent form, indicating their understanding of the purpose and procedures of the clinical trial and their willingness to participate in the study.