In medicine, immunodeficiency (or immune deficiency) is a state where the immune system's ability to defend the organism from infectious disease is compromised or entirely absent. Most cases of immunodeficiency are either congenital or acquired.

Congenital immune deficiency

A number of rare diseases feature a heightened susceptibility to infections from childhood onward. Many of these disorders are hereditary and autosomal recessive. Examples include myeloperoxidase deficiency, Wiskott-Aldrich syndrome, chronic granulomatous disease, and severe combined immunodeficiency.

Acquired immune deficiency

Although elderly people are generally more susceptible to infections, this can be increased in the presence of a number of blood disorders (see hematology); important examples are multiple myeloma and chronic lymphatic leukemia (CLL).

Immune suppression is a common side-effect of many drugs, most importantly chemotherapy. This feature is used to suppress immune activity in autoimmune disorders with DMARDs. Any drug that causes neutropenia and/or agranulocytosis can cause immune suppression and sepsis.

Immune deficiency is also the hallmark of Acquired Immunodeficiency Syndrome (AIDS). The HIV virus destroys CD4⁺-T-lymphocytes (Helper T cells), leading to opportunistic infections.

See also

• Immune system