Hyper-IgM syndrome is characterized by normal or high levels of immunoglobulin M (IgM) and decreased levels or absence of other immunoglobulins. As a result, people are more susceptible to bacterial infections.
Children with hyper-IgM syndrome have frequent sinus and lung infections.
Doctors diagnose the disorder by measuring levels of immunoglobulins in the blood and by doing genetic tests.
Treatment involves immune globulin, antibiotics to prevent infections, and, when possible, stem cell transplantation.
(See also Overview of Immunodeficiency Disorders.)
IgM is one of 5 types of antibodies, which help defend the body against infection. The level of IgM is elevated or sometimes normal in hyper-IgM syndrome, but this is not the cause of the immunodeficiency. Other immunoglobulins are absent or at low levels. The lack of these other immunoglobulins makes people with hyper-IgM syndrome less able to fight off infection.
Hyper-IgM syndrome is a primary immunodeficiency disorder. It may be inherited in one of the following ways:
As an X-linked disorder: That is, it is due to a mutation in a gene on the X (sex) chromosome. X-linked disorders usually affect only boys.
As an autosomal recessive disorder: That is, 2 genes for the disorder, one from each parent, are required.
Most cases of hyper-IgM syndrome are X-linked.
How the disorder affects people varies depending on which gene is affected.
X-linked hyper-IgM syndrome
In X-linked hyper-IgM syndrome, B cells produce only IgM, not other types of immunoglobulin. Levels of IgM may be normal or high.
Infants with this form often develop pneumonia due to the fungus Pneumocystis jirovecii. Children have frequent sinus and lung infections during the first 2 years of life.
Many children die before puberty, and those who live longer often develop cirrhosis or lymphoma.
Autosomal recessive hyper-IgM syndrome
Generally, symptoms are similar to those of the X-linked form.
There are several autosomal recessive forms. In some of them, the lymph nodes, spleen, and tonsils are enlarged, and autoimmune disorders may develop. In autoimmune disorders, the immune system attacks the body's own tissue.
Diagnosis of Hyper-IgM Syndrome
Blood tests
Genetic testing
Doctors suspect hyper-IgM syndrome based on symptoms. They then measure levels of immunoglobulins. High or normal levels of IgM and low levels or absence of other immunoglobulins support the diagnosis.
When possible, the diagnosis is confirmed by genetic testing.
Prenatal genetic testing can be offered to women considering pregnancy if they have family members with certain gene mutations that can cause hyper-IgM syndrome.
Treatment of Hyper-IgM Syndrome
Immune globulin
Sometimes an antibiotic to prevent infections
Stem cell transplantation when possible
People with hyper-IgM syndrome are usually given immune globulin to replace some of the missing immunoglobulins. Immune globulin consists of antibodies obtained from the blood of people with a normal immune system.
Pneumocystis jirovecii infection.
Stem cell transplantation from a sibling with the same tissue type is done when possible.
More Information
The following English-language resource may be useful. Please note that The Manual is not responsible for the content of this resource.
Immune Deficiency Foundation: Hyper-IgM syndrome: Comprehensive information on hyper-IgM syndrome, including information on diagnosis and treatment and advice for people affected
