Hyper IgM syndrome

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Hyper IgM syndrome
Classification and external resources
Immunoglobulin M
ICD-10	D80.5
ICD-9	279.05
eMedicine	ped/2457
MeSH	D053306

Hyper IgM syndrome is a family of autosomal recessive 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.

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.

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.

Pneumocystis pneumonia

Infections with Pneumocystis pneumonia are common in infants with Hyper IgM syndrome.

External links

GeneReviews/NCBI/NIH/UW entry on X-Linked Hyper IgM Syndrome or Immunodeficiency with Hyper-IgM, Type 1

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.

Immune disorders: Lymphoid and complement immunodeficiency (D80–D85, 279.0–4)

Primary

Antibody/humoral (B)

Hypogammaglobulinemia	X-linked agammaglobulinemia Transient hypogammaglobulinemia of infancy

Dysgammaglobulinemia	IgA deficiency IgG deficiency IgM deficiency Hyper IgM syndrome (2 3 4 5) Wiskott-Aldrich syndrome Hyper-IgE syndrome

Other	Common variable immunodeficiency ICF syndrome

T cell deficiency (T)

thymic hypoplasia: hypoparathyroid (Di George's syndrome)
euparathyroid (Nezelof syndrome
Ataxia telangiectasia)

peripheral: Purine nucleoside phosphorylase deficiency

Hyper IgM syndrome (1)

Severe combined (B+T)

x-linked: X-SCID
autosomal: Adenosine deaminase deficiency
Omenn syndrome
ZAP70 deficiency
Bare lymphocyte syndrome

Acquired

AIDS

Leukopenia:
Lymphocytopenia

Idiopathic CD4+ lymphocytopenia

Complement deficiency

C1-inhibitor (Angioedema/Hereditary angioedema)
Complement 2 deficiency/Complement 4 deficiency
MBL deficiency
Properdin deficiency
Complement 3 deficiency
Terminal complement pathway deficiency
Paroxysmal nocturnal hemoglobinuria
Complement receptor deficiency

M: LMC

cell/phys/auag/auab/comp, igrc

imdf/ipig/hyps/tumr

proc, drug (L3/4)

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