This is a prospective cohort study to observe the efficacy and safety of Tofacitinib in children with Blau syndrome (BS). The investigators would analyze the rate of remission or low disease activity after treatment as well as changes in inflammatory markers, patients' and physician's global assessment of disease activity to determine the efficacy and safety of Tofacitinib.

Inclusion Criteria:

• Patients who have pathogenic mutation(s) in NOD2 gene;
• Patients who have clinical manifestations such as granulomatous dermatitis, arthritis, uveitis, vasculitis, interstitial lung disease and so on;
• Clinical remission was not achieved after ≥12 weeks of treatment with at least one immunosuppressant or biologics.

Exclusion Criteria:

Patients will not be included if meets any of the following criteria:

• Being treated with IL-1 inhibitor, or other biological agents;
• Pregnant and lactating women;
• Serious organ function failure, expected life time less than 6 months.