Treatment of Non Severe Hemophagocytosis Lymphohistiocytosis With ITACITINIB

Inclusion Criteria: * Patients age \> 18 years, * Patient is willing to provide written informed consent prior to enrolment and agrees to follow the protocol * Patient known to have systemic juvenile idiopathic arthritis are classified as having HLH * Negative pregnancy test for woman of childbearing potential, woman of childbearing potential should have reliable contraception for the duration of the study * Be either affiliated to, or a beneficiary of, a social security category Exclusion Criteria: * Organ failure: confusion, organic kidney failure KDIGO 2 criteria, liver failure (Factor V \< 50%), heart failure, respiratory failure. * Fibrinogen \< 0.50 g/l, platelets \<20G/L * Indication to intensive care unit transfer on an organ failure requiring assistance (dialysis, Ventilation (assisted or VNI), shock regardless of the origin. * Breastfeeding women * Patient participating in another investigational therapeutic study * Women with a positive pregnancy test or not willing to take contraceptive measures * Known allergies, hypersensitivity, or intolerance to any of the ITACITINIB or excipients, or similar compounds * Current or history of recurrent infections, including HBV, HCV * Participants with active HBV or HCV infection that requires treatment or who are at risk for HBV reactivation (ie Positive HBs Ag serology) * Candidates positive for HCV antibody and positive PCR RNA HCV * HIV infection with positive viral charge * Protected adults (including individual under guardianship by court order) * Vulnerable adults, under a safeguard of justice measure * Adults deprived of their liberty by judicial or administrative decision * Persons under psychiatric care without their consent * Persons admitted to social institution for purposes other this research * Adults under legal protection (guardianship or curatorship) * Persons unable to express their consent