Classic ataxia-telangiectasia (A-T) is characterized by progressive cerebellar ataxia beginning between ages one and four years, oculomotor apraxia, choreoathetosis, telangiectasias of the conjunctivae, immunodeficiency, frequent infections, and an increased risk for malignancy, particularly leukemia and lymphoma. Individuals with A-T are unusually sensitive to ionizing radiation. Non-classic forms of A-T have included adult-onset A-T and A-T with early-onset dystonia.

The phenotypic spectrum of X-linked severe combined immunodeficiency (X-SCID) ranges from typical X-SCID (early-onset disease in males that is fatal if not treated with hematopoietic stem cell transplantation [HSCT] or gene therapy) to atypical X-SCID (later-onset disease comprising phenotypes caused by variable immunodeficiency, immune dysregulation, and/or autoimmunity). Typical X-SCID. Prior to universal newborn screening (NBS) for SCID most males with typical X-SCID came to medical attention between ages three and six months because of recurrent infections, persistent infections, and infections with opportunistic organisms. With universal NBS for SCID, the common presentation for typical X-SCID is now an asymptomatic, healthy-appearing male infant. Atypical X-SCID, which usually is not detected by NBS, can manifest in the first years of life or later with one of the following: recurrent upper and lower respiratory tract infections with bronchiectasis; Omenn syndrome, a clinical phenotype caused by immune dysregulation; X-SCID combined immunodeficiency (often with recurrent infections, warts, and dermatitis); immune dysregulation and autoimmunity; or Epstein-Barr virus-related lymphoproliferative complications.

Immunodeficiency-67 (IMD67) is an autosomal recessive primary immunodeficiency characterized by recurrent severe systemic and invasive bacterial infections beginning in infancy or early childhood. The most common organisms implicated are Streptococcus pneumoniae and Staphylococcus aureus; Pseudomonas and atypical Mycobacteria may also be observed. IMD67 is life-threatening in infancy and early childhood. The first invasive infection typically occurs before 2 years of age, with meningitis representing up to 41% of the bacterial infections. The mortality rate in early childhood is high, with most deaths occurring before 8 years of age. Affected individuals have an impaired inflammatory response to infection, including lack of fever and neutropenia, although erythrocyte sedimentation rate (ESR) and C-reactive protein may be elevated. General immunologic workup tends to be normal, with normal levels of B cells, T cells, and NK cells. However, more detailed studies indicate impaired cytokine response to lipopolysaccharide (LPS) and IL1B (147720) stimulation; response to TNFA (191160) is usually normal. Patients have good antibody responses to most vaccinations, with the notable exception of pneumococcal vaccination. Viral, fungal, and parasitic infections are not generally observed. Early detection is critical in early childhood because prophylactic treatment with IVIg or certain antibiotics is effective; the disorder tends to improve naturally around adolescence. At the molecular level, the disorder results from impaired function of selective Toll receptor (see TLR4, 603030)/IL1R (see IL1R1, 147810) signaling pathways that ultimately activate NFKB (164011) to produce cytokines (summary by Ku et al., 2007; Picard et al., 2010; Grazioli et al., 2016). See also IMD68 (612260), caused by mutation in the MYD88 gene (602170), which shows a similar phenotype to IMD67. As the MYD88 and IRAK4 genes interact in the same intracellular signaling pathway, the clinical and cellular features are almost indistinguishable (summary by Picard et al., 2010).

A rare genetic primary immunodeficiency with characteristics of increased susceptibility to fungal infections that typically manifest as recurrent, chronic mucocutaneous candidiasis, systemic candidiasis with meningoencephalitis and deep dermatophytosis. Dermatophytes invade skin, hair, nails, lymph nodes and brain, resulting in erythematosquamous lesions, nodular subcutaneous or ulcerative infiltrations, severe onychomycosis and lymphadenopathy.

Any common variable immunodeficiency in which the cause of the disease is a mutation in the MS4A1 gene.

Any common variable immunodeficiency in which the cause of the disease is a mutation in the CD81 gene.

Immunodeficiency-18 is an autosomal recessive primary immunodeficiency characterized by onset in infancy or early childhood of recurrent infections. The severity is variable, encompassing both a mild immunodeficiency and severe combined immunodeficiency (SCID), resulting in early death without bone marrow transplantation in some patients. Immunologic work-up of the IMD18 SCID patients shows a T cell-negative, B cell-positive, natural killer (NK) cell-positive phenotype, whereas T-cell development is not impaired in the mild form of IMD18 (summary by de Saint Basile et al., 2004).

IMD52 is an autosomal recessive primary immunodeficiency with variable manifestations, including severe combined immunodeficiency, hematologic autoimmune disorders, progressive lymphopenia and hypogammaglobulinemia, and lymphoproliferation with splenomegaly. Patients develop severe recurrent infections from infancy, and most die without bone marrow transplantation. The variable clinical features result from a defect in T-cell receptor signaling (summary by Keller et al., 2016 and Bacchelli et al., 2017).

X-linked lymphoproliferative disease (XLP) has two recognizable subtypes, XLP1 and XLP2. XLP1 is characterized predominantly by one of three commonly recognized phenotypes: Inappropriate immune response to Epstein-Barr virus (EBV) infection leading to hemophagocytic lymphohistiocytosis (HLH) or severe mononucleosis. Dysgammaglobulinemia. Lymphoproliferative disease (malignant lymphoma). XLP2 is most often characterized by HLH (often associated with EBV), dysgammaglobulinemia, and inflammatory bowel disease. HLH resulting from EBV infection is associated with an unregulated and exaggerated immune response with widespread proliferation of cytotoxic T cells, EBV-infected B cells, and macrophages. Dysgammaglobulinemia is typically hypogammaglobulinemia of one or more immunoglobulin subclasses. The malignant lymphomas are typically B-cell lymphomas, non-Hodgkin type, often extranodal, and in particular involving the intestine.

ZAP70-related combined immunodeficiency (ZAP70-related CID) is a cell-mediated immunodeficiency caused by abnormal T-cell receptor (TCR) signaling. Affected children usually present in the first year of life with recurrent bacterial, viral, and opportunistic infections, diarrhea, and failure to thrive. Severe lower-respiratory infections and oral candidiasis are common. Affected children usually do not survive past their second year without hematopoietic stem cell transplantation (HSCT).

Infantile-onset multisystem autoimmune disease-3 (ADMIO3) is an autosomal recessive disorder of immune dysregulation characterized by the onset of various systemic autoimmune manifestations in the first months or years of life. Features may include hypothyroidism, type 1 diabetes mellitus, systemic inflammatory manifestations (fever, hepatomegaly), and autoimmune cytopenias. Laboratory studies show normal levels of T, B, and NK cells, but CD4+ (see 186940) T cells demonstrate hyperproliferation when stimulated in vitro (Janssen et al., 2022). For a discussion of genetic heterogeneity of ADMIO, see ADMIO1 (615952).