Selective immunoglobulin A deficiency is also a primary immunodeficiency. Primary immunodeficiencies leading to phagocyte deficiency include chronic granulomatous disease and leukocyte adhesion deficiency syndrome. Primary immunodeficiencies leading to complement deficiency include hereditary angioedema, deficiency of C3, deficiency of membrane attack complex, and C2 or C4 deficiency secondary to autoimmunity. Primary immunodeficiencies leading to both T-cell and B-cell deficiency include severe combined immunodeficiency disease, Wiskott-Aldrich syndrome, immunodeficiency with ataxia-telangiectasia, and Major Histocompatibility Complex deficiency. Primary immunodeficiency leading to B-cell deficiency includes X-linked agammaglobulinemia, also called Bruton agammaglobulinemia. Primary immunodeficiencies leading to T-cell deficiency include DiGeorge syndrome, also known as congenital thymic aplasia, chronic mucocutaneous candidiasis, hyper-immunoglobulin M syndrome, and interleukin-12 receptor deficiency. Primary immunodeficiency is subdivided into types that cause T-cell deficiency, B-cell deficiency, both T-cell and B-cell deficiency, complement deficiency, phagocyte deficiency, and immunoglobulin A deficiency. Immunodeficiencies can be primary or secondary. Immunodeficiency results from a failure or absence of elements of the immune system, including lymphocytes, phagocytes, and the complement system.

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