Evans syndrome is a rare disorder in which the body’s immune system produces antibodies that mistakenly destroy red blood cells, platelets and sometimes certain white blood cell known as neutrophils. This leads to abnormally low levels of these blood cells in the body (cytopenia). The premature destruction of red blood cells (hemolysis) is known as autoimmune hemolytic anemia or AIHA. Thrombocytopenia refers to low levels of platelets (idiopathic thrombocytopenia purpura or ITP in this instance). Neutropenia refers to low levels of certain white blood cells known as neutrophils. Evans syndrome is defined as the association of AIHA along with ITP; neutropenia occurs less often. In some cases, autoimmune destruction of these blood cells occurs at the same time (simultaneously); in most cases, one condition develops first before another condition develops later on (sequentially). The symptoms and severity of Evans syndrome can vary greatly from one person to another. Evans syndrome can potentially cause severe, life-threatening complications. Evans syndrome may occur by itself as a primary (idiopathic) disorder or in association with other autoimmune disorders or lymphoproliferative disorders as a secondary disorder. (Lymphoproliferative disorders are characterized by the overproduction of white blood cells.) The distinction between primary and secondary Evans syndrome is important as it can influence treatment.
Evans syndrome was first described in the medical literature in 1951 by Dr. Robert Evans and associates. For years, the disorder was considered a coincidental occurrence of AIHA with thrombocytopenia and/or neutropenia. However, researchers now believe that the disorder represents a distinct condition characterized by a chronic, profound (more than in ITP or AIHA alone) state of immune system malfunction (dysregulation).