From OMIM
XLP2 is an X-linked primary immune deficiency with symptom onset usually in the first years of life, although later onset may occur. Features are compatible with immune dysregulation and include hemophagocytic lymphohistiocytosis (HLH), often associated with chronic Epstein-Barr virus (EBV) infection, splenomegaly, fever, colitis or inflammatory bowel disease (IBD), and recurrent infections. Laboratory abnormalities are variable, but can include hypogammaglobulinemia, cytopenias, and low levels of a particular subset of T cells known as NKT (or iNKT) cells. Functional studies show increased sensitivity of T cells to apoptosis (activation-induced cell death, AICD), impaired cytokine production, including of TNF-alpha (TNFA; 191160), and general dysregulation of the immune pathway, such as increased levels of IL18 (600953). However, circulating levels of lymphocytes and NK cells are usually normal. Many patients die from fulminant HLH, and the only curative treatment is a hematopoietic stem cell transplant, although this procedure has been associated with a poor prognosis. Female mutation carriers are usually asymptomatic, although some female carriers may have less severe manifestations, which appears to depend on X-inactivation patterns (summary by Yang et al., 2012; review by Latour and Aguilar, 2015). Latour and Aguilar (2015) provided a detailed review of XIAP deficiency, including clinical features, molecular genetics, and pathophysiology. For a general phenotypic description and a discussion of genetic heterogeneity of X-linked lymphoproliferative syndrome, see XLP1 (308240).  http://www.omim.org/entry/300635

From MedlinePlus Genetics
Without treatment, most people with XLP survive only into childhood. Death usually results from hemophagocytic lymphohistiocytosis.

Cancers of immune system cells (lymphomas) occur in about one-third of people with XLP.

About one-third of people with XLP experience dysgammaglobulinemia, which means they have abnormal levels of some types of antibodies. Antibodies (also known as immunoglobulins) are proteins that attach to specific foreign particles and germs, marking them for destruction. Individuals with dysgammaglobulinemia are prone to recurrent infections.

People with XLP may respond to EBV infection by producing abnormally large numbers of T cells, B cells, and other lymphocytes called macrophages. This proliferation of immune cells often causes a life-threatening reaction called hemophagocytic lymphohistiocytosis. Hemophagocytic lymphohistiocytosis causes fever, destroys blood-producing cells in the bone marrow, and damages the liver. The spleen, heart, kidneys, and other organs and tissues may also be affected. In some individuals with XLP, hemophagocytic lymphohistiocytosis or related symptoms may occur without EBV infection.

XLP can be divided into two types based on its genetic cause and pattern of signs and symptoms: XLP1 (also known as classic XLP) and XLP2. People with XLP2 have not been known to develop lymphoma, are more likely to develop hemophagocytic lymphohistiocytosis without EBV infection, usually have an enlarged spleen (splenomegaly), and may also have inflammation of the large intestine (colitis). Some researchers believe that these individuals should actually be considered to have a similar but separate disorder rather than a type of XLP.

X-linked lymphoproliferative disease (XLP) is a disorder of the immune system and blood-forming cells that is found almost exclusively in males. More than half of individuals with this disorder experience an exaggerated immune response to the Epstein-Barr virus (EBV). EBV is a very common virus that eventually infects most humans. In some people it causes infectious mononucleosis (commonly known as "mono"). Normally, after initial infection, EBV remains in certain immune system cells (lymphocytes) called B cells. However, the virus is generally inactive (latent) because it is controlled by other lymphocytes called T cells that specifically target EBV-infected B cells.  https://medlineplus.gov/genetics/condition/x-linked-lymphoproliferative-disease