Type Description X-linked<unk>  Most cases of<unk>  are due to mutations in the IL2RG gene encoding the common gamma chain (γc) (CD132), a protein that is shared by the receptors for interleukins IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. These interleukins and their receptors are involved in the development and differentiation of T and B cells. Because the common gamma chain is shared by many interleukin receptors, mutations that result in a non-functional common gamma chain cause widespread defects in interleukin signalling. The result is a near complete failure of the immune system to develop and function, with low or absent T cells and NK cells and non-functional B cells.The common gamma chain is encoded by the gene IL-2 receptor gamma, or IL-2Rγ, which is located on the X-chromosome. For this reason, immunodeficiency caused by mutations in IL-2Rγ is known as X-linked<unk> . The condition is inherited in an X-linked recessive pattern. Adenosine deaminase deficiency The second most common form of<unk>  after X-SCID is caused by a defective enzyme, adenosine deaminase (ADA), necessary for the breakdown of purines. Lack of ADA causes accumulation of dATP. This metabolite will inhibit the activity of ribonucleotide reductase, the enzyme that reduces ribonucleotides to generate deoxyribonucleotides. The effectiveness of the immune system depends upon lymphocyte proliferation and hence dNTP synthesis. Without functional ribonucleotide reductase, lymphocyte proliferation is inhibited and the immune system is compromised. Purine nucleoside phosphorylase deficiency An autosomal recessive disorder involving mutations of the purine nucleoside phosphorylase (PNP) gene. PNP is a key enzyme in the purine salvage pathway. Impairment of this enzyme causes elevated dGTP levels resulting in T-cell toxicity and deficiency. Reticular dysgenesis Inability of granulocyte precursors to form granules secondary to mitochondrial adenylate kinase 2 (AK2) malfunction. Omenn syndrome The manufacture of immunoglobulins requires recombinase enzymes derived from the recombination activating genes RAG-1 and RAG-2. These enzymes are involved in the first stage of V(D)J recombination, the process by which segments of a B cell or T cell's DNA are rearranged to create a new T cell receptor or B cell receptor (and, in the B cell's case, the template for antibodies).Certain mutations of the RAG-1 or RAG-2 genes prevent V(D)J recombination, causing<unk> . Bare lymphocyte syndrome Type 1: MHC class I is not expressed on the cell surface. The defect is caused by defective TAP proteins, not the MHC-I protein. Type 2: MHC class II is not expressed on the cell surface of all antigen presenting cells. Autosomal recessive. The MHC-II gene regulatory proteins are what is altered, not the MHC-II protein itself. JAK3 Janus kinase-3 (JAK3) is an enzyme that mediates transduction downstream of the γc signal. Mutation of its gene causes<unk> . DCLRE1C DCLRE1C "Artemis" is a gene required for DNA repair and V(D)J recombination. A recessive loss-of-function mutation found the Navajo and Apache population causes<unk>  and radiation intolerance.
Severe combined immunodeficiency
Common variable immunodeficiency
X-linked severe combined immunodeficiency
X-linked agammaglobulinemia
Primary immunodeficiency
Combined immunodeficiencies
Chronic granulomatous disease
Adult-onset immunodeficiency syndrome