Hyper-IgM syndrome is characterized by normal or elevated levels of immunoglobulin M (IgM) and decreased levels or the absence of other immunoglobulins. As a result, people are more susceptible to bacterial infections.
Children with hyper-IgM syndrome have frequent infections of the sinuses and lungs.
The disorder is diagnosed by measuring the concentration of immunoglobulins in the blood and using genetic tests.
Treatment includes administration of immunoglobulin concentrates, antibiotics to prevent infection, and, where possible, stem cell transplantation.
Hyper-IgM syndrome is a primary immunodeficiency disorder. It can be inherited in the following ways:
As an X-linked disorder: that is, as a hereditary immunodeficiency due to a mutation in a gene located on the X (sexual) chromosome. X-linked disorders usually occur only in males.
As an autosomal recessive disorder: that is, two genes for the disease are required to present it, one from each parent.
Most cases of hyper-IgM syndrome (excess immunoglobulin M) are linked to the X chromosome.
The type of involvement of people suffering from this disorder depends on which gene is affected.
IgM levels may be elevated or normal. Other immunoglobulins may be absent, or have low levels. Lack of other immunoglobulins makes people with hyper-IgM syndrome less able to fight infection.
X-linked hyper-IgM syndrome
In X-linked hyper-IgM syndrome, B cells produce only IgM, they do not produce any other type of immunoglobulin. IgM levels can be normal or high.
Babies with this disorder often develop pneumonia from the fungus Pneumocystis jirovecii. Children have frequent lung and sinus 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, the symptoms are similar to those of the X-linked form.
There are various autosomal recessive forms. In some of them, the lymph nodes, spleen and tonsils are enlarged, and autoimmune disorders can appear.
- Blood test
- Genetic testing
Doctors suspect hyper-IgM syndrome based on symptoms. From this information, they resort to determining immunoglobulin levels. High or normal IgM levels accompanied by low levels or the absence of other immunoglobulins support the diagnosis.
When possible, the diagnosis is confirmed by genetic testing.
Prenatal genetic testing may be offered to women who want to become pregnant and have family members with certain genetic mutations that can cause hyper-IgM syndrome.
- Sometimes an antibiotic to prevent infection
- When possible, stem cell transplant
People with hyper-IgM syndrome are usually given immunoglobulin concentrates to replace some of the immunoglobulins that they lack. Immunoglobulin concentrates consist of antibodies obtained from the blood of people with a normal immune system.
Some people with some forms of this syndrome receive trimethoprim / sulfamethoxazole (an antibiotic) to avoid Pneumocystis jirovecii infection.
When possible, transplant stem cells from a sibling with the same tissue type.