A lymphoproliferative disorder is a medical condition characterized by the dysfunction of the immune system often resulting in excessive production of lymphocytes or white blood cells. The immune system is the body's defense against infections and diseases caused by invading organisms such as bacteria and viruses. Many cases of lymphoproliferative disorders occur in individuals from any age group with compromised immune systems. Affected individuals are prone to develop severe infections. Malignancy or cancer may also develop as a result of a lymphoproliferative disorder.

Lymphocytes are produced in the bone marrow and are usually found in the blood circulation, lymph nodes, and spleen. Lymph nodes are distributed throughout the body to fight against infection. The spleen, located in the left upper section of the abdomen, stores blood and also protects the body against infection. In lymphoproliferative disorder, increased lymphocytes in the bloodstream can lead to the enlargement of the lymph nodes and the spleen.

Many cases of lymphoproliferative disorders originate from inherited conditions and sometimes are caused by acquired immune system dysfunction. Other cases, however, have no known cause. Examples of lymphoproliferative disorders are ataxia telangiectasia, Wiskott-Aldrich syndrome, and autoimmune lymphoproliferative syndrome (ALPS). These conditions are often a result of genetic mutations inherited from one or both parents, and may occur in both men and women.

An X-linked lymphoproliferative syndrome is another inherited form of lymphoproliferative disorder that mostly affects men. Many men with this form of lymphoproliferative disorder have increased susceptibility to develop infections from Epstein-Barr virus (EVB). EBV, also known as herpesvirus 4, is often the cause of infectious mononucleosis. Symptoms of infectious mononucleosis include lymph node enlargement, fever, and sore throat. These patients may develop lymphoma, a cancer affecting the immune system, and aplastic anemia, a condition marked by failure of the bone marrow to produce new blood cells.

One acquired cause of lymphoproliferative disorder in children includes an infection with the human immunodeficiency virus (HIV). HIV-infected mothers often pass the virus to their children during pregnancy, during delivery, or through breast milk. Another acquired cause of lymphoproliferative disorder occurs after organ transplant procedures and use of immunosuppressive drugs. Immunosuppressive drugs are administered in order to suppress the immune system from rejecting the new organ.

Diagnostic tools usually employed in the evaluation of patients with lymphoproliferative disorders include a complete blood count (CBC), blood test to detect EBV infection, bone scan, X-ray, and magnetic resonance imaging (MRI). A team of doctors often manages a patient with a lymphoproliferative disorder. These include the oncologists, doctors who specialize in cancer management, surgeons, and other medical specialists whose expertise may be needed depending on the extent of the patient's condition.