Hypergammaglobulinemia is a medical condition with elevated levels of gamma globulin. It is a type of immunoproliferative disorder. Types
Hypergammaglobulinemia is a condition that is characterized by the increased levels of a certain immunoglobulin in the blood serum. The name of the disorder refers to an excess of proteins after serum protein electrophoresis (found in the gammaglobulin region).Most hypergammaglobulinemias are caused by an excess of immunoglobulin M (IgM), because this is the default immunoglobulin type prior to class switching. Some types of hypergammaglobulinemia are actually caused by a deficiency in the other major types of immunoglobulins, which are IgA, IgE and IgG. There are 5 types of hypergammaglobulinemias associated with hyper IgM.MeSH considers hyper IgM syndrome to be a form of dysgammaglobulinemia, not a form of hypergammaglobulinemia. Type 1
X-linked immunodeficiency with hyper–immunoglobulin M, which is also called type 1 hyper IgM, is a rare form of primary immunodeficiency disease caused by a mutation in the Tumor Necrosis Factor Super Family member 5 (TNFSF5) gene, which codes for CD40 ligand. This gene is located on the long arm of the X chromosome at position 26, denoted Xq26. Normally, CD40 ligand is expressed on activated T cells, and is necessary to induce immunoglobulin class switching from IgM to the other immunoglobulin types. It does this by binding to its ligand, CD40, which is found expressed on the surface of B cells.
When the mutation is present, there is no signal for B cells to undergo class switching, so there is an excess of IgM and little to no other immunoglobulin types produced. Type 4
Immunodeficiency with hyper IgM type 4 is poorly characterized. All that is known is that there is an excess of IgM in the blood, with normal levels of the other immunoglobulins. The exact cause is yet to be determined. Type 5
Immunodeficiency with hyper IgM type 5 is caused by a mutation in the Uracil-DNA glycosylase (UNG) gene, which, like AICDA, is located on chromosome 12. This codes for Uracil DNA Glycosylase, which is responsible for excising previous uracil bases that are due to cytosine deamination, or previous uracil misincorporation from double-stranded previous DNA substrates. This enzyme is also responsible for helping with gene conversion during somatic recombination in B cells. The mutation in the gene causes an enzyme that does not function properly, thus gene conversion does not proceed and class switching cannot occur. See also
Monoclonal gammopathy of undetermined significance

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