AIHA is a group of anaemia in which increased hemolysis is caused by
antibodies directed against the patient's own RBCs. These autoantibodies are
usually of Ig Type.
- 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
- 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
- RBC encounters splenic macrophages may
result in phagocytosis of the entire cell
- Idiopathic 50%
- Secondary 50%
- Drugs: methyl dopa, mefenamic acid and L-dopa
- Malignancy of lymphoreticular system
- Systemic lupus erythematosus (SLE)
- Rheumatoid arthritis
- Ulcerative colitis
- Paroxysmal cold haemoglobinuria (PCH)
- Mycoplasma pneumonia
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
- 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
- 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
- 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.