Children and Adult Hemophagocytic Syndrome (HLHa)

Different study of HLHa patients : * Diagnosis criteria, because criteria are based on pediatric genetic studies. * Physiopathological studies: genetic studies have demonstrated the role of CD8+ cells, in particular because they have a genetic defect affecting their cytotoxic functions in HLH pediatric. the aim is to establish if the same defect is found in both some or in all of HLHa patients. If this is the case, to then establish whether hypomorphic genetic mutations are responsible.