XLP is an extremely rare disease affecting only males . The disease is thought to affect less than 1 child in a million . The disease can manifest in many forms. The three most common are fatal infectious mononucleosis (FIM), dysgammaglobunemia, and malignant lymphoma. Less common problems may include aplastic anemia and vasculitis. The average age of onset is 2.5 years of age and nearly 75% of the children are deceased before 10 years of age. The oldest known survivor was 44 years of age. Exposure to EBV(mononucleosis) is not required for disease forms other than FIM.

EBV is a widespread herpes virus, more common than the chicken pox. It affects about 90% of our population by adulthood. EBV infection in infants and children is usually asymptomatic, but in adolescents and adults glandular fever is often seen. In males with XLP, an uncontrolled increase in the number of T and B cells in response to mono often leads to death from liver or bone marrow failure. Children with XLP who survive EBV can later develop lymphomas or other forms of this disease. The only definitive treatment currently available is allogenic (donor) bone marrow transplants. IgG therapy will not protect against EBV.