Efficacy and Safety of Thalidomide for Pediatric PFAPA Syndrome

Inclusion Criteria: 1. Meet the 2019 Eurofever or 2020 CARRA diagnostic criteria for PFAPA syndrome. 2. Aged 3 to 18 years (inclusive) at the time of screening. 3. Have experienced at least 3 febrile episodes within the past six months. 4. History of responsiveness to glucocorticoid treatment during at least 3 previous episodes, but with continued recurrence. (Responsiveness is defined as normalization of body temperature within 24 hours after a maximum dose of 2 mg/kg \[up to 60 mg\] administered as a single or two divided doses). Exclusion Criteria: 1.Diagnosis of monogenic or other polygenic periodic fever syndromes. 2.Presence of immunodeficiency or neoplastic diseases. 3.Active bacterial, fungal, or viral infection during the screening period. 4.Prior treatment with immunosuppressive agents. 5.Prior use of thalidomide or colchicine. 6.Laboratory parameters at screening that meet any of the following (based on the most recent test result at the study hospital prior to the first dose): 1. White Blood Cell (WBC) count \< 4 × 10⁹/L, Hemoglobin (HGB) \< 100 g/L, or Platelet (PLT) count \< 100 × 10⁹/L. 2. Serum Alanine Aminotransferase (ALT) \> 2 times the Upper Limit of Normal (ULN). 3. Glomerular Filtration Rate (GFR/CCR) \< 60 mL/min/1.73m².