Hyper IgM syndrome
| Hyper IgM syndrome | |
|---|---|
| Classification and external resources | |
 Immunoglobulin M |
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| ICD-10 | D80.5 |
| ICD-9 | 279.05 |
| eMedicine | ped/2457 |
| MeSH | D053306 |
Hyper IgM syndrome is a family of genetic disorders in which the level of Immunoglobulin M (IgM) antibodies is relatively high. The most common type is a result of a defect in a Th2 cell protein (CD40 ligand). The disorder causes immunodeficiencies, including a higher than normal susceptibility to various types of infections. Individuals with hyper-IgM syndrome typically also have a low number of neutrophils and platelets.
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[edit] Pathophysiology
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. Generally, in people with hyper IgM syndromes, the B cells keep making IgM antibodies because they can't switch to a different kind of antibody. This results in an overproduction of IgM antibodies and an underproduction of all other types, IgA, IgG, and IgE.
[edit] Types
Five types have been characterized:
- Hyper-IgM syndrome type 1, characterized by mutations of the CD40LG gene. In this type, T cells cannot tell B cells to switch classes.
- Hyper-IgM syndrome type 2, characterized by mutations of the AICDA gene. In this type, B cells cannot recombine genetic material to change heavy chain production, which is a required step in switching classes.
- Hyper-IgM syndrome type 3, characterized by mutations of the CD40 gene. In this type, B cells cannot receive the signal from T cells to switch classes.
- Hyper-IgM syndrome type 4, which is a defect in class switch recombination downstream of the AICDA gene that does not impair Somatic Hyper Mutation.[1]
- Hyper-IgM syndrome type 5, characterized by mutations of the UNG gene.
[edit] Pneumocystis pneumonia
Infections with Pneumocystis pneumonia are common in infants with Hyper IgM syndrome.
[edit] External links
[edit] References
- ^ Lougaris V, Badolato R, Ferrari S, Plebani A (2005). "Hyper immunoglobulin M syndrome due to CD40 deficiency: clinical, molecular, and immunological features". Immunol. Rev. 203: 48–66. doi:10.1111/j.0105-2896.2005.00229.x. PMID 15661021. http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0105-2896&date=2005&volume=203&spage=48.
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