This study aimed to investigate the efficacy and safety of different doses of ruxolitinib as a salvage therapy for refractory/relapsed hemophagocytic lymphohistiocytosis(HLH).

Inclusion Criteria:

1. meet hemophagocytic lymphohistiocytosis (HLH)-04 diagnostic criteria;
2. treated with HLH-94 no less than 2 weeks before enrollment and did not achieve at least PR; or relapsed patients after remission；
3. Life expectancy exceeds 1 month;
4. Age≥1 year old and ≤75 years old, gender is not limited；
5. Before the start of the study, total bilirubin ≤ 10 times the upper limit of normal; serum creatinine ≤ 1.5 times normal；
6. Serum human immunodeficiency virus(HIV) antigen or antibody negative；
7. Hepatitis C virus (HCV) antibody is negative, or HCV antibody is positive, but HCV RNA is negative；
8. Both hepatitis B virus (HBV) surface antigen and HBV core antibody were negative. If any of the above is positive, peripheral blood hepatitis B virus DNA titer should be detected, and less than 1×103 copies/ml can enter the group；
9. Informed consent.

Exclusion Criteria:

1. Pregnancy or lactating Women；
2. Allergic to ruxolitinib；
3. Active bleeding of the internal organs；
4. uncontrollable infection；
5. Serious mental illness;
6. Non-melanoma skin cancer history;
7. Patients unable to comply during the trial and/or follow-up phase;
8. Participate in other clinical research at the same time.