| A rare, genetic, primary immunodeficiency disorder characterized by an abnormal immune response to Epstein-Barr virus (EBV) infection, caused by hemizygous mutations in the X-linked XIAP gene, resulting in B cell lymphoproliferation and manifesting with various phenotypes which include EBV-driven hemophagocytic lymphohistiocytosis, hypogammaglobulinemia, recurrent splenomegaly, hepatitis, colitis, and intestinal bowel disease with features of Crohn's disease. Additional manifestations include variable auto-inflammatory symptoms such as uveitis, arthritis, skin abscesses, erythema nodosum, and nephritis. Neurological involvement is rare, and lymphoma is never observed. Laboratory findings include normal or increased activated T cells, low or normal iNKT cells, and normal or reduced memory B cells. |
