Immunodeficiency
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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). HIV destroys CD4+-T-lymphocytes (Helper T cells), leading to opportunistic infections.