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.
(See also Overview of Immunodeficiency Disorders Overview of Immunodeficiency Disorders Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual. Immunodeficiency... read more .)
T cells T cells One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more 
are white blood cells that identify and attack foreign cells and substances. Natural killer cells Components of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more are a type of T cell that recognizes and kills abnormal cells (such as certain infected cells and cancer cells). Deficiency or malfunction of T cells increases the risk of serious infection.
X-linked lymphoproliferative syndrome is a primary immunodeficiency disorder Primary immunodeficiency Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual. Immunodeficiency... read more . It is inherited as an X-linked recessive Recessive x-linked disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body or code for functional RNA molecules.... read more 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 Infectious Mononucleosis Epstein-Barr virus causes a number of diseases, including infectious mononucleosis. The virus is spread through kissing. Symptoms vary, but the most common are extreme fatigue, fever, sore throat... read more 
. The EBV causes several disorders, including infectious mononucleosis. Also, natural killer cells do not function.
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.
Symptoms of X-Linked Lymphoproliferative Syndrome
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 Overview of Lymphoma Lymphomas are cancers of lymphocytes, which reside in the lymphatic system and in blood-forming organs. Lymphomas are cancers of a specific type of white blood cells known as lymphocytes. These... read more 
, aplastic anemia Aplastic Anemia Aplastic anemia is a disorder in which the cells of the bone marrow that develop into mature blood cells are damaged, leading to low numbers of red blood cells, white blood cells, and/or platelets... read more , another immunodeficiency disorder, and an enlarged spleen Enlarged Spleen An enlarged spleen is not a disease in itself but the result of an underlying disorder. Many disorders can make the spleen enlarge. Many disorders, including infections, anemias, and cancers... read more .
About 75% of people die by age 10, and all die by age 40 unless stem cell transplantation is done.
Diagnosis of X-Linked Lymphoproliferative Syndrome
Blood tests
Genetic testing
Sometimes bone marrow biopsy
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.
Laboratory and imaging tests are done yearly to check for lymphoma and anemia. Sometimes a bone marrow biopsy is done for these reasons.
Genetic testing is recommended for family members.
Prenatal genetic screening Prenatal Diagnostic Testing Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more is recommended for people if a mutation that causes X-linked lymphoproliferative syndrome has been identified in their family.
Treatment of X-Linked Lymphoproliferative Syndrome
Stem cell transplantation
About 80% of people who receive a stem cell transplant Stem Cell Transplantation Stem cell transplantation is the removal of stem cells (undifferentiated cells) from a healthy person and their injection into someone who has a serious blood disorder. (See also Overview of... read more survive. But without transplantation, three quarters of people die before age 10 years, and all die by age 40. 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.
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: Other primary cellular immunodeficiencies: General information on primary cellular immunodeficiencies, including information on diagnosis and treatment
