A secondary form of HLH, Hemophagocytic inflammatory syndrome (HIS), has been described in selected Inborn Errors of Immunity (IEI) as in defects of MAGT1, GATA2 WAS, and ADA2 genes, but also in patients with chronic granulomatous disease (CGD) and severe combined immunodeficiencies (SCID) (3, 4), as a deficit of ILRG2, RAG1, IL7RA, CD3E, and Adenosine Deaminase-SCID (ADA-SCID) (5, 6). Here, ADA is linked to severe combined immunodeficiency.