• Source: Hyper-IgM syndrome type 2

Hyper IgM syndrome type 2 is a rare disease. Unlike other hyper-IgM syndromes, type 2 patients identified thus far did not present with a history of opportunistic infections. One would expect opportunistic infections in any immunodeficiency syndrome. The responsible genetic lesion is in the AICDA gene found at 12p13.




Hyper IgM syndromes


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 IgM levels and a considerable deficiency in Immunoglobulins G (IgG), A (IgA) and E (IgE). As a consequence, people with HIGM have an increased susceptibility to infections.




Signs and symptoms


Hyper IgM syndrome can have the following syndromes:

Infection/Pneumocystis pneumonia (PCP), which is common in infants with hyper IgM syndrome, is a serious illness. PCP is one of the most frequent and severe opportunistic infections in people with weakened immune systems.
Hepatitis (hepatitis C)
Chronic diarrhea
Hypothyroidism
Neutropenia
Arthritis
Encephalopathy (degenerative)




Cause



Different genetic defects cause HIgM syndrome, the vast majority are inherited as an X-linked recessive genetic trait and most with the condition are male.
IgM is the form of antibody that all B cells produce initially before they undergo class switching. 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 can not switch to a different antibody. This results in an overproduction of IgM antibodies and an underproduction of IgA, IgG, and IgE.




Pathophysiology


CD40 is a costimulatory receptor on B cells that, when bound to CD40 ligand (CD40L), sends a signal to the B-cell receptor. When there is a defect in CD40, this leads to defective T-cell interaction with B cells. Consequently, humoral immune response is affected. Patients are more susceptible to infection.




Diagnosis


The diagnosis of hyper IgM syndrome can be done via the following methods and tests:

MRI
Chest radiography
Pulmonary function test
Lymph node test
Laboratory test (to measure CD40)




Treatment


In terms of treatment for hyper IgM syndrome, there is the use of allogeneic hematopoietic cell transplantation. Additionally, anti-microbial therapy, use of granulocyte colony-stimulating factor, immunosuppressants, as well as other treatments, may be needed.




References

Kata Kunci Pencarian:

• Hyper IgM syndrome
• Hyper-IgM syndrome type 2
• Hyper-IgM syndrome type 5
• Hyper-IgM syndrome type 1
• Hyper-IgM syndrome type 4
• Hyper-IgM syndrome type 3
• List of syndromes
• Type 2
• Hypersensitivity
• Hypergammaglobulinemia