X-linked lymphoproliferative syndrome 2

The X-linked lymphoproliferative syndrome (XLP) is a rare, inherited immunodeficiency that is characterized by lymphohystiocytosis, hypogammaglobulinaemia and lymphomas, and that usually develops in response to infection with Epstein-Barr virus (EBV). Mutations in the signalling lymphocyte activation molecule (SLAM)-associated protein SAP, a signalling adaptor molecule, underlie 60% of cases of familial XLP. Another procent of cases is due to defects in in the gene that encodes the X-linked inhibitor-of-apoptosis XIAP (BIRC4) required for the survival and/or differentiation of NKT cells and also a potent regulator of lymphocyte homeostasis in vivo. BIRC4 are the cause of lymphoproliferative syndrome x-linked type 2 (XLP2).

Alternative names


Lymphoproliferative syndrome X-linked type 2, XIAP deficiency


  • Other well-defined immunodeficiency syndromes




#300635 Lymphoproliferative syndrome, x-linked, 2; XLP2

#308240 Lymphoproliferative syndrome

*300079 Baculoviral IAP repeat-containing protein 4; BIRC4

Cross references

Phenotypically related immunodeficiencies

IDR factfile for X-linked lymphoproliferative disease (Duncan disease)


XLP affects about 3 out of every 1,000,000 males,