The exact prevalence of Evans syndrome is unknown. As it is the case with many autoimmune conditions, females appear to be affected more commonly than men, with a female to male ratio of 3:2. Evans syndrome is also more common during childhood but it can occur in adults as well.

Evans syndrome can be classified as idiopathic (unknown cause) or secondary to another condition. The exact cause of idiopathic Evans syndrome is unknown, although it is believed to be a result of the dysregulation of the immune system. The deficiency of certain molecules involved in the regulation of the immune system is among the possible explanations. Secondary Evans syndrome has been associated with other conditions including autoimmune lymphoproliferative syndrome, systemic lupus erythematosus, and autoimmune hepatitis, all of which are autoimmune conditions targeting different organs, as well as chronic lymphocytic leukemia which is a type of cancer affecting the blood and the bone marrow.

Symptoms of Evans syndrome can vary among individuals and depend on the specific type of blood cell that is affected. If red blood cells are damaged, hemolytic anemia can occur which is a condition in which red blood cells are produced but are destroyed faster than in healthy individuals. Symptoms of hemolytic anemia include an abnormally pale-looking skin, fatigue, weakness, dizziness, shortness of breath, and jaundice. Jaundice is a condition caused by high levels of a substance called bilirubin which causes the white of the eye and the skin to appear yellow. 

When platelets are affected, thrombocytopenia or abnormally low levels of platelets result. Thrombocytopenia leads to easy bruising and bleeding as blood does not effectively clot. In addition, red, brown, or purple dots or larger spots (petechiae and purpura) that are often clustered together may appear on the skin as a result of bleeding. 

If white blood cells are affected, the individual becomes prone to recurrent infections. They may also notice sores inside their mouth or experience fever. 

In each individual, only one type of blood cell might be affected, or multiple blood cell types could be damaged concurrently. Furthermore, affected individuals may experience the symptoms over a long period of time or as intermittent episodes of relapse and remission. 

To diagnose Evans syndrome, a number of blood tests are performed to look for low red blood cell count, thrombocytopenia, or an increase in certain other markers such as bilirubin. If test results indicate Evans syndrome, other tests are performed to determine whether it is idiopathic or secondary Evans syndrome. If all possible underlying conditions have been ruled out, idiopathic Evans syndrome is diagnosed. If additional testing indicates an underlying condition, secondary Evans syndrome is diagnosed.

The diagnosis of Evans syndrome involves taking a blood sample to check for features of autoimmune hemolytic anemia, a condition in which red blood cells are attacked and destroyed by the immune system. A direct antiglobulin test (DAT) is among such tests. DAT is a test that can determine whether hemolytic anemia is caused by the attack of the immune system. This is achieved by looking for defensive proteins (antibodies) that are attached to red blood cells, indicating that the immune system is targeting these cells. Other tests may be done to determine whether there is an underlying cause. For example, a blood sample may be tested for the presence of certain markers that indicate other autoimmune conditions such as autoimmune hepatitis, Graves disease, or rheumatoid arthritis. 

Treatment of Evans syndrome usually starts with corticosteroids which are a group of anti-inflammatory drugs that can also lower the activity of the immune system. Although inflammation is a natural immune process, excessive inflammation can damage healthy tissue. Corticosteroids are often given for weeks if thrombocytopenia (low platelet count) is present without hemolytic anemia and for months is hemolytic anemia is also present. In addition, intravenous immune globulin (IVIG) may also be administered for patients. IVIG involves the administration of a blood product containing immune proteins (antibodies) obtained from many donors. The use of IVIG is less common if only hemolytic anemia is present without thrombocytopenia. 

If the individual does not respond to corticosteroids and IVIG or in case of relapse after treatment, administration of rituximab may be considered. Rituximab is a drug that is used to treat certain autoimmune conditions and cancers by slowing the growth of particular groups of immune cells. Although some people do not respond to rituximab at all, others experience long periods of remission following treatment. Rituximab is particularly effective in the case of Evans syndrome that is secondary to systemic lupus erythematosus or a tumor. 

Finally, in some cases, a splenectomy or the surgical removal of the spleen might be considered. However, splenectomy is becoming less common as a treatment option for Evans syndrome due to a low response rate, higher possibility of relapse, and the chance of complications. A splenectomy could lead to immediate improvement but relapses are common and occur within a few months after the procedure. In some individuals, a splenectomy may result in remission for long periods of time. 

The outlook of Evans syndrome varies among individuals. Some may experience long periods of remission when their symptoms disappear or improve over time. The effectiveness of treatment is also variable. Others may not have any remissions. Individuals affected by Evans syndrome are more likely to develop other autoimmune conditions. In some cases, severe infections and bleeding (hemorrhage) may occur. Evans syndrome could potentially become fatal in some affected individuals.

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