Warm type autoimmune hemolytic anemia (WAIHA)

Warm antibody hemolytic anemia associated with autoantibodies that react optimally at 37’C.

Warm antibody hemolytic anemia leads to accelerated red blood cell destruction due to presence of of warm agglutinins, which are almost always IgG antibodies, that bind to antigens on erythrocytes at a temperature of 37°C.

Most patients have antibodies, usually IgG detectable in the serum and one third will have cold agglutinins detectable at room temperatures with a normal titer.

Occurs at any age and can be acute, transient or chronic in nature.

Most common type of autoimmune hemolytic anemia with an incidence of 1:50-100,000.

More frequent in females and in older individuals.

Median age of onset is 52 years, but may occur at any age.

Up to 30% of patients have a durable remission after initial therapy, but the rest have chronic and a and relapsing history.

Majority of cases are due to polyclonal IgG, although rarely IgM and IgA may be involved.

The Rh system is the most common target of the autoantibodies.

Most cases are IgG1 and IgG3 subclasses which can fix complement.

Red blood cell destruction generally takes place via an extravascular process in the liver and spleen.

IgG coded red cells are recognized by splenic macrophages, which carry Fcgamma receptors for the IgG heavy chain.

The above leads to phagocytosis of the red blood cell, or more commonly removal of a portion of the red cell membrane, that results in microspherocytes that are visualized on a peripheral blood smear.

Direct Coombs test is positive.

Blood smear shows microspherocytes.

Indirect Coombs positive in about 60% of cases.

Approximately 67% have positive Coombs test to IgG and complement, 20% positive for IgG and not complement and positive for complement 13% but not IgG.

About 5% have Coombs negative disease.

Warm antibodies are panagglutins because they cause agglutination of all red blood cells part of standard test panels.

Half of cases are idiopathic in nature with the remaining cases associated with an underlying disorder or drug reaction.

Hemolysis may be immediately responsive to steroid or splenectomy treatment, but may be resistant to all measures.

Most common underlying disorders are chronic lymphocytic leukemia and B cell lymphoma.

Associated with an increased incidence in patients receiving purine nucleoside analogues such as fludarabine and cladibrine for hematologic malignancies.

Associated with autoimmune diseases such as lupus erythematosus.

Patients with chronic disease are subject to increased risk of venous thromboembolism.

Thrombotic events have been reported in 11 to 20% of patients with autoimmune hemolytic anemia, mostly deep venous thrombosis.

Treatment options include transfusion, steroid therapy, splenectomy, immunosuppressive chemotherapy, danazol and intravenous gammaglobulin.

Mild disease may not require treatment.

When hemolysis is severe or symptomatic transfusions may be required.

Initial treatment is the use of corticosteroids.

In patients who do not respond to, or relapse on corticosteroid splenectomy is curable in half to two thirds of patients.

All individuals should receive folic acid supplementation.

Approximately 80% of patients respond to corticosteroids, but permanent control occurs in 20%.

In patients who have resistant disease cytotoxic chemotherapy or intravenous gammaglobulin may be helpful.

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