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Related Subjects: |Alpha Thalassaemia |Anaemia of Chronic Disease |Aplastic anaemia(AML) |Autoimmune Haemolytic anaemia (AIHA)

AIHA is a group of anaemia in which increased haemolysis is caused by antibodies directed against the patient's own RBCs. These autoantibodies are usually of Ig Type.

About

• Antibodies to red cells shorten red cell survival
• May be an IgG or IgM (rarely IgE or IgA)
• Complement fixation leads to intravascular haemolysis
• The antibody can be more active at differing temperatures
• Those working best at 37°C are warm abs and less than 37°C are cold antibodies

Aetiology

• There are antibodies directed against red blood cell (RBC) surface antigens
• These are found on RBCs and antihuman Globulin will cause agglutination
• Rhesus (Rh) polypeptides are the most common targets with warm-type AIHA
• RBC encounters splenic macrophages may result in phagocytosis of the entire cell

Causes

• Idiopathic 50%
• Secondary 50%
  • Drugs: methyldopa, mefenamic acid and L-dopa
  • Malignancy of lymphoreticular system
  • Systemic lupus erythematosus (SLE)
  • Rheumatoid arthritis
  • Ulcerative colitis
  • Paroxysmal cold haemoglobinuria (PCH)
  • Mycoplasma pneumonia
  • Cytomegalovirus

Classification by temperature reacts with RBC

• Warm antibodies: reacts best at 37°C
  • The majority are warm antibodies and IgG
  • Commoner, Autoimmune diseases, SLE, Drugs, Lymphomas
  • Steroids are often used and Splenectomy may be indicated
  • Some cases require azathioprine and cyclophosphamide
• Cold antibodies: reacts best at lower temperatures
  • Usually IgM and maximum activity usually at 4°C with a positive Coomb's test
  • Complement mediated intravascular haemolysis
  • Haemolysis occurs at cold peripheries
  • Mycoplasma, Infectious Mononucleosis - EBV, Lymphomas
  • Chronic form in elderly with peripheral cyanosis

Clinical

• Weakness, pallor and jaundice and dark urine
• May have splenomegaly in addition to jaundice and pallor.
• Those with cold agglutinin disease may have dark urine in cold weather

Investigations

• FBC: Anaemia may be found. The anaemia is macrocytic due to the marked reticulocytosis.
• Blood smear often reveals the presence of polychromatophilia and spherocytes.
• Haemolysis: raised LDH, peripheral blood smear, raised serum bilirubin, low serum haptoglobin
• The Direct Coomb's is positive (DAT) for both types when antihuman Globulin (AHG) serum causes red cells to agglutinate.
• Warm have Coomb's positive at 37°C and usually IgG
• Cold have Coomb's positive at 4°C and usually IgM

Management

• Supportive. Transfuse if needed. Treat underlying cause.
• Withdraw any cause e.g. likely causative drugs
• COLD: Tends to be transient and do not generally require treatment. Treat cause and advice to avoid cold peripheries - gloves, avoid cold weather and outdoors.

References

• Diagnostic approach to microangiopathic haemolytic disorders