Subacute sclerosing panencephalitis (SSPE) is a fatal neurodegenerative disease caused by persistent central nervous system infection with the measles virus (summary by Torisu et al., 2004).

X-linked agammaglobulinemia (XLA) is characterized by recurrent bacterial infections in affected males in the first two years of life. Recurrent otitis is the most common infection prior to diagnosis. Conjunctivitis, sinopulmonary infections, diarrhea, and skin infections are also frequently seen. Approximately 60% of individuals with XLA are recognized as having immunodeficiency when they develop a severe, life-threatening infection such as pneumonia, empyema, meningitis, sepsis, cellulitis, or septic arthritis. S pneumoniae and H influenzae are the most common organisms found prior to diagnosis and may continue to cause sinusitis and otitis after diagnosis and the initiation of gammaglobulin substitution therapy. Severe, difficult-to-treat enteroviral infections (often manifesting as dermatomyositis or chronic meningoencephalitis) can be prevented by this treatment. The prognosis for individuals with XLA has improved markedly in the last 25 years as a result of earlier diagnosis, the development of preparations of gammaglobulin that allow normal concentrations of serum immunoglobulin G to be achieved, and more liberal use of antibiotics.

IGHD3 is characterized by agammaglobulinemia and markedly reduced numbers of B cells, short stature, delayed bone age, and good response to treatment with growth hormone (summary by Conley et al., 1991). For general phenotypic information and a discussion of genetic heterogeneity of IGHD, see 262400.

Bare lymphocyte syndrome type II (BLS II) is an inherited disorder of the immune system categorized as a form of combined immunodeficiency (CID). People with BLS II lack virtually all immune protection from bacteria, viruses, and fungi. They are prone to repeated and persistent infections that can be very serious or life-threatening. These infections are often caused by "opportunistic" organisms that ordinarily do not cause illness in people with a normal immune system.\n\nBLS II is typically diagnosed in the first year of life. Most affected infants have persistent infections in the respiratory, gastrointestinal, and urinary tracts. Because of the infections, affected infants have difficulty absorbing nutrients (malabsorption), and they grow more slowly than their peers. Eventually, the persistent infections lead to organ failure. Without treatment, individuals with BLS II usually do not survive past early childhood.\n\nIn people with BLS II, infection-fighting white blood cells (lymphocytes) are missing specialized proteins on their surface called major histocompatibility complex (MHC) class II proteins, which is where the condition got its name. Because BLS II is the most common and best studied form of a group of related conditions, it is often referred to as simply bare lymphocyte syndrome (BLS).

Familial hemophagocytic lymphohistiocytosis-2 (FHL2) is an autosomal recessive disorder of immune dysregulation with onset in infancy or early childhood. It is characterized clinically by fever, edema, hepatosplenomegaly, and liver dysfunction. Neurologic impairment, seizures, and ataxia are frequent. Laboratory studies show pancytopenia, coagulation abnormalities, hypofibrinogenemia, and hypertriglyceridemia. There is increased production of cytokines, such as gamma-interferon (IFNG; 147570) and TNF-alpha (191160), by hyperactivation and proliferation of T cells and macrophages. Activity of cytotoxic T cells and NK cells is reduced, consistent with a defect in cellular cytotoxicity. Bone marrow, lymph nodes, spleen, and liver show features of hemophagocytosis. Chemotherapy and/or immunosuppressant therapy may result in symptomatic remission, but the disorder is fatal without bone marrow transplantation (summary by Dufourcq-Lagelouse et al., 1999, Stepp et al., 1999, and Molleran Lee et al., 2004). For a general phenotypic description and a discussion of genetic heterogeneity of FHL, see 267700.

Any primary immunodeficiency disease in which the cause of the disease is a mutation in the BCL10 gene.

Familial Hemophagocytic lymphohistiocytosis (FHL) is a rare primary immunodeficiency characterized by a macrophage activation syndrome with an onset usually occurring within a few months or less common several years after birth.

X-linked lymphoproliferative disease (XLP) in general is characterized by an inappropriate immune response to Epstein-Barr virus (EBV) infection leading to hemophagocytic lymphohistiocytosis (HLH) or severe mononucleosis, dysgammaglobulinemia, and lymphoproliferative disease (malignant lymphoma). The condition primarily affects males. XLP has two recognizable subtypes, XLP1 (due to pathogenic variants in SH2D1A) and XLP2 (due to pathogenic variants in XIAP). HLH / fulminant infectious mononucleosis is the most common presentation regardless of subtype. HLH is characterized as an acute illness with prolonged and high fever, bi- or trilineage cytopenias, and hepatosplenomegaly, which is often severe or fatal. Death is generally secondary to liver failure or multisystem organ dysfunction. In those with XLP1, dys- or hypogammaglobulinemia can lead to varying degrees of humoral immune dysfunction associated with bronchiectasis and recurrent respiratory infections that, if untreated, may result in death. Lymphoproliferative disease (malignant lymphoma) and other lymphoproliferative diseases are specific to XLP1 and often develop in childhood, usually following EBV exposure. Rarer findings in those with XLP1 can include aplastic anemia, vasculitis, and lymphoid granulomatosis. Males with XLP2 are more likely to have HLH without EBV infection, recurrent episodes of HLH (which is not typically seen in those with XLP1), splenomegaly, and gastrointestinal disease, including enterocolitis and perirectal abscesses or fistulae. Rarely, individuals with XLP2 and inflammatory bowel disease have been reported to develop inflammatory liver disease, which can progress to fatal liver failure. Transient hypogammaglobulinemia has been rarely observed in those with XLP2. To date, neither lymphoproliferative disease nor common variable immunodeficiency has been reported in males with XLP2. Heterozygous females rarely have symptoms. There are, however, increasing numbers of reports of affected females with unfavorable (skewed) X-chromosome inactivation favoring the X chromosome with the pathogenic variant who develop HLH, inflammatory bowel disease, and erythema nodosum.