Hyper IgM syndrome

Hyper IgM syndrome
Immunoglobulin M
Classification and external resources
Specialty	hematology
ICD-10	D80.5
ICD-9-CM	279.05
eMedicine	ped/2457
MeSH	D053306
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Hyper IgM syndromes is a group of primary immune deficiency disorders characterized by defective CD40 signaling; via B cells affecting class switch recombination (CSR) and somatic hypermutation. Immunoglobulin (Ig) class switch recombination deficiencies are characterized by elevated serum Immunoglobulin M (IgM) levels and a considerable deficiency in Immunoglobulins G (IgG), A (IgA) and E (IgE). As a consequence, people with HIGM have decreased concentrations of serum IgG and IgA and normal or elevated IgM, leading to increased susceptibility to infections.

Five types of hyper IgM syndrome have been characterized:

Among the presentation consistent with hyper IgM syndrome are the following:

Different genetic defects cause HIgM syndrome, the vast majority are inherited as an X-linked recessive genetic trait and most sufferers are male.

IgM is the form of antibody that all B cells produce initially, before they undergo class switching due to exposure to a recognized antigen. Healthy B cells efficiently switch to other types of antibodies as needed to attack invading bacteria, viruses, and other pathogens. In people with hyper IgM syndromes, the B cells keep making IgM antibodies because they can't switch to a different antibody. This results in an overproduction of IgM antibodies and an underproduction of IgA, IgG, and IgE.

In the mechanism one sees that CD40, protein is a receptor for cells of the human immune system, furthermore, is important in immune and inflammatory response. When CD40L is not working properly, this then leads to defective T-cell interaction with monocytes. Consequently, resulting cell-mediated immune response is affected, therefore certain infections have a greater opportunity to invade the human body.

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