Autoimmune haemolytic anemia

Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is a rare but serious condition in which the immune system mistakenly attacks and destroys the body's own red blood cells, leading to hemolysis (the destruction of red blood cells) and anemia. This condition can be classified into different types based on the temperature at which the antibodies react with red blood cells: warm antibody AIHA, cold agglutinin disease, and mixed-type AIHA.

Pathophysiology

AIHA occurs when the immune system produces antibodies that target red blood cells as if they were foreign invaders. These antibodies bind to the red blood cells, marking them for destruction by the spleen or causing them to be destroyed directly in the bloodstream. The destruction of red blood cells leads to a decrease in their number, resulting in anemia.

Warm Antibody AIHA

Warm antibody AIHA is the most common form of the disease and is characterized by the presence of IgG antibodies that react with red blood cells at body temperature (37°C). These antibodies often lead to extravascular hemolysis, primarily in the spleen.

Cold Agglutinin Disease

Cold agglutinin disease involves IgM antibodies that react with red blood cells at lower temperatures, typically below 30°C. This form of AIHA often results in intravascular hemolysis and can be triggered by cold exposure.

Mixed-Type AIHA

Mixed-type AIHA involves both warm and cold antibodies, leading to a combination of intravascular and extravascular hemolysis.

Causes

The exact cause of AIHA is often unknown, but it can be associated with other autoimmune disorders, infections, certain medications, or lymphoproliferative disorders. In some cases, AIHA is idiopathic, meaning no underlying cause is identified.

Symptoms

Symptoms of AIHA can vary depending on the severity of the anemia and the rate of hemolysis. Common symptoms include:

• Fatigue
• Pallor
• Shortness of breath
• Jaundice
• Dark urine
• Rapid heart rate

Diagnosis

The diagnosis of AIHA is based on clinical evaluation, laboratory tests, and the exclusion of other causes of hemolytic anemia. Key diagnostic tests include:

• Complete blood count (CBC)
• Reticulocyte count
• Direct antiglobulin test (Coombs test)
• Peripheral blood smear

Treatment

Treatment of AIHA depends on the severity of the condition and the underlying cause. Common treatment options include:

• Corticosteroids (e.g., prednisone)
• Immunosuppressive drugs
• Intravenous immunoglobulin (IVIG)
• Blood transfusions
• Splenectomy (in refractory cases)

Prognosis

The prognosis of AIHA varies. Some patients respond well to treatment and achieve remission, while others may experience chronic or relapsing disease. Early diagnosis and appropriate management are crucial for improving outcomes.

Also see

• Anemia
• Immune system
• Autoimmune disease
• Hemolysis
• Spleen