X-linked Lymphoproliferative Syndrome
(See also Overview of Immunodeficiency Disorders.)
X-linked lymphoproliferative syndrome results from an abnormality in T cells and natural killer cells and results in an abnormal response to Epstein-Barr virus infection.
People with X-linked lymphoproliferative syndrome develop a serious, sometimes fatal form of infectious mononucleosis after being infected with Epstein-Barr virus.
Doctors diagnose the disorder by genetic testing and sometimes other tests.
Stem cell transplantation is necessary for survival and may cure the disorder.
X-linked lymphoproliferative syndrome is a primary immunodeficiency disorder. It is inherited as an X-linked recessive disorder. X-linked means that the disorder is due to a mutation in one or more genes on the X (sex) chromosome. X-linked recessive disorders occur only in boys.
There are two types, which result from different gene mutations but cause similar symptoms.
In the first type, too many white blood cells (which help the body fight infection) are produced in response to Epstein-Barr virus (EBV) infection. The EBV causes several disorders, including infectious mononucleosis. Also, natural killer cells do not function. Natural killer cells are a type of white blood cell that recognizes and kills abnormal cells (such as certain infected cells and cancer cells).
The second type can cause a rare but serious disorder called hemophagocytic lymphohistiocytosis, which causes immunodeficiency in infants and young children. In hemophagocytic lymphohistiocytosis, too many blood cells in the immune system are activated. The result is widespread inflammation. Sometimes this overactivation is triggered by infectious organisms such as EBV.
Usually, people with X-linked lymphoproliferative syndrome have no symptoms until Epstein-Barr virus (EBV) infection develops. Then, a serious, sometimes fatal form of infectious mononucleosis develops. The liver malfunctions, resulting in liver failure. People who survive develop other disorders, such as lymphoma, aplastic anemia, another immunodeficiency disorder, and an enlarged spleen.
About 75% of people die by age 10, and all die by age 40 unless stem cell transplantation is done.
Doctors suspect X-linked lymphoproliferative syndrome in young boys who have severe EBV infection, other characteristic problems, or family members with similar symptoms.
The diagnosis is confirmed by genetic testing. However, genetic testing can take weeks to complete, so doctors may do specialized blood tests, such as flow cytometry (analysis of proteins on the surface of white blood cells), to check for abnormalities in immune cells. Sometimes a bone marrow biopsy is done.
Laboratory and imaging tests are done yearly to check for lymphoma and anemia.
Genetic testing is recommended for family members.
Prenatal genetic screening is recommended for people if a mutation that causes X-linked lymphoproliferative syndrome has been identified in their family.
About 80% of people who receive a stem cell transplant survive. Transplantation can cure X-linked lymphoproliferative syndrome if it is done before EBV infection or other disorders become too severe.
Rituximab (a drug that modifies the immune system's activity) can help prevent severe EBV infection before transplantation is done.