Agammaglobulinemia, x-linked

X-linked agammaglobulinemia is classified as a primary immunodeficiency disorder. There are more than 250 different disorders in this group. They are rare, chronic disorders in which some part of the immune system does not function properly. They are caused by a change in a gene that affects the immune system. In X-linked agammaglobulinemia, people lack antibodies, the specialized proteins that help the body to fight off bacteria, viruses and other foreign substances.