Autoimmune Hemolytic Anemia

Definition

Definition of Autoimmune Hemolytic Anemia
Autoimmune hemolytic anemia (or autoimmune haemolytic anaemia; AIHA) occurs when antibodies directed against the person's own red blood cells (RBCs) cause them to burst (lyse), leading to insufficient plasma concentration. The lifetime of the RBCs is reduced from the normal 100-120 days to just a few days in serious cases. The intracellular components of the RBCs are released into the circulating blood and into tissues, leading to some of the characteristic symptoms of this condition. The antibodies are usually directed against high-incidence antigens, therefore they also commonly act on allogenic RBCs (RBCs originating from outside the person themselves, e.g. in the case of a blood transfusion) AIHA is a relatively rare condition, affecting one to three people per 100,000 per yea.

Symptoms

Symptoms of Autoimmune Hemolytic Anemia
Some people with autoimmune hemolytic anemia may have no symptoms, especially when the destruction of red blood cells is mild and develops gradually. Others have symptoms similar to those that occur with other types of anemia, especially when the destruction is more severe or rapid. When severe or rapid destruction of red blood cells occurs, mild jaundice may also develop. When destruction persists for a few months or longer, the spleen may enlarge, resulting in a sense of abdominal fullness and, occasionally, discomfort.

When the cause of autoimmune hemolytic anemia is another disease, symptoms of the underlying disorder, such as swollen and tender lymph nodes and fever, may dominate.

Causes

Causes of Autoimmune Hemolytic Anemia
The causes of AIHA are poorly understood. The disease may be primary, or secondary to another underlying illness. The primary illness is idiopathic (the two terms being used synonymously). Idiopathic AIHA accounts for approximately 50% of cases. Secondary AIHA can result from many other illnesses. Warm and cold type AIHA each have their own more common secondary causes. The most common causes of secondary warm-type AIHA include lymphoproliferative disorders (e.g. chronic lymphocytic leukemia, lymphoma) and other autoimmune disorders (e.g. systemic lupus erythematosis, rheumatoid arthritis, scleroderma, ulcerative colitis). Less common causes of warm-type AIHA include neoplasms other than lymphoid, and infection. Secondary cold type AIHA is also primarily caused by lymphoproliferative disorders, but is also commonly caused by infection, especially by mycoplasma, viral pneumonia, infectious mononucleosis and other respiratory infections. Less commonly, it can be caused by concomitant autoimmune disorders.

Diagnosis

Diagnosis of Autoimmune Hemolytic Anemia
Diagnosis is made by first ruling out other causes of hemolytic anemia, such as G6PD, thalassemia, sickle-cell disease, etc. Clinical history is also important to elucidate any underlying illness or medications which may have led to the disease.

Following this, laboratory investigations are carried out to determine the etiology of the disease. A positive DAT test has poor specificity for AIHA (having many differential diagnoses); so supplemental serological testing is required to ascertain the cause of the positive reaction. Hemolysis must also be demonstrated in the lab. The typical tests used for this are a CBC with peripheral smear, bilirubin, LDH (in particular with isoenzyme 1), haptoglobin and urine hemoglobin.

Treatment

Treatment of Autoimmune Hemolytic Anemia
Much literature exists regarding the treatment of AIHA. Efficacy of treatment depends on the correct diagnosis of either warm or cold type AIHA.

Warm type AIHA is usually a more insidious disease, not treatable by simply removing the underlying cause. First line therapy for this is usually with corticosteroids, such as prednisolone. Following this, other immunosuppressants are considered, such as rituximab, danazol, cyclophosphamide, azathioprine or cyclosporine.

Cold agglutinin disease is treated by avoiding the cold or sometimes with rituximab. Removal of the underlying cause is also important.

Paroxysmal cold hematuria is treated by removing the underlying cause, such as infection.

Prognosis

Prognosis of Autoimmune Hemolytic Anemia
Consult with your doctor.

Prevention

Prevention of Autoimmune Hemolytic Anemia
Consult with your doctor.