XLP2 is a type of X-linked lymphoproliferative disease. XLP2 typically affects males. It can also occasionally affect females. The condition was first described in 2006. Only about 100 young males have been diagnosed with it so far.
XLP2 is caused by a change in the XIAP gene. This is sometimes called the BIRC4 gene.
The XIAP gene codes for the XIAP protein that the body needs to regulate the immune system. People with this genetic change either have problems with the XIAP protein, or they do not have the protein. Another name for this condition is XIAP deficiency. This is a unique disorder. The term we use is “XIAP deficiency.”
XIAP deficiency is an “X-linked” disease. This means that the genes that cause it are on the X chromosome. Males have one X chromosome and one Y chromosome. Females have two X chromosomes. If a male has a changed XIAP gene on his X chromosome, he will develop XIAP deficiency.
For a female to develop XIAP deficiency, she would need to have genetic changes on both X chromosomes. Another way she could develop XIAP deficiency would be by a “skewing” of X-chromosome inactivation. This causes many cells to be deficient in XIAP. Most females with a genetic change are just carriers. They do not develop symptoms of XIAP / XLP2.
Females who are affected by XIAP deficiency most commonly develop inflammatory bowel disease. But they can also develop other problems caused by XIAP deficiency. Females who are affected or who are carriers can pass the disease on to their male children. The chance of this happening is 50%. They can also pass carrier status or, more rarely, the disease to their female children.
The symptoms for XIAP deficiency can vary from person to person. The symptoms can vary even within the same family. Children with XIAP deficiency are at risk for many diseases and health problems, including:
Children with the other type of X-linked lymphoproliferative disease, XLP1, are at increased risk for lymphoma, which is a type of blood cancer. Children with XLP2 / XIAP deficiency do not develop lymphoma as a result of their condition.
Between 67% and 90% of children with XIAP develop hemophagocytic lymphohistiocytosis (HLH). This is a potentially life-threatening disorder of the immune system that causes organ damage.
Signs and symptoms of HLH include:
Some children with XIAP deficiency develop some symptoms of HLH. These include fever, low blood counts and enlarged spleens. But they do not have the “full picture” of HLH. This is considered “incomplete HLH.”
About one-quarter to one-third of children with XIAP deficiency develop lower-than-normal antibody levels or hypogammaglobulinemia. Signs and symptoms include:
Between 17% and 22% of children with XIAP develop inflammatory bowel disease. This condition leads to inflammation in the gastrointestinal tract. It causes symptoms such as:
If your child develops symptoms of XIAP deficiency, your doctor may refer you to a hematologist, rheumatologist or immunologist. The doctor may provide:
Currently, the only cure for XIAP deficiency is allogeneic hematopoietic stem cell transplantation. This is sometimes called a bone marrow transplant. These transplants replace diseased blood-forming stem cells with healthy ones. Not all patients with XIAP deficiency need a transplant.
If your child has XIAP deficiency, ongoing care from an experienced team of specialists is very important. The care team can provide an accurate diagnosis and comprehensive treatment plan to help your child have the best outcome possible. If needed, the care team can include specialists from many areas of medicine, such as a pediatric gastroenterologist.
Treatment for children with XIAP deficiency may include:
Some children with XIAP deficiency should not have live virus vaccines because of their abnormal immune system. These vaccines include chickenpox / varicella; rotavirus; and measles, mumps and rubella (MMR).
Last Updated 12/2024
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