Autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited disorder in which the body cannot properly regulate the number of immune system cells (lymphocytes). ALPS is characterized by the production of an abnormally large number of lymphocytes (lymphoproliferation). Accumulation of excess lymphocytes results in enlargement of the lymph nodes (lymphadenopathy), the liver (hepatomegaly), and the spleen (splenomegaly).

Autoimmune disorders are also common in ALPS. Autoimmune disorders occur when the immune system malfunctions and attacks the body's own tissues and organs. Most of the autoimmune disorders associated with ALPS target and damage blood cells. For example, the immune system may attack red blood cells (autoimmune hemolytic anemia), white blood cells (autoimmune neutropenia), or platelets (autoimmune thrombocytopenia). Less commonly, autoimmune disorders that affect other organs and tissues occur in people with ALPS. These disorders can damage the kidneys (glomerulonephritis), liver (autoimmune hepatitis), eyes (uveitis), or nerves (Guillain-Barre syndrome). Skin problems, usually rashes or hives (urticaria), can also occur in ALPS.

ALPS can have varying patterns of signs and symptoms. Most commonly, lymphoproliferation becomes apparent during childhood. Enlargement of the lymph nodes and spleen frequently occur in affected individuals. Autoimmune disorders typically develop several years later, most frequently as a combination of hemolytic anemia and thrombocytopenia, also called Evans syndrome. People with this classic form of ALPS generally have a near-normal lifespan, but have a greatly increased risk of developing cancer of the immune system cells (lymphoma) compared with the general population.

Some people have signs and symptoms that resemble those of ALPS, including lymphoproliferation, lymphadenopathy, splenomegaly, and low blood counts, but the specific pattern of these signs and symptoms or the genetic cause may be different. Researchers disagree whether individuals with these non-classic forms should be considered to have ALPS or a separate condition.