Essay 5- Autoimmune haemolytic anemias
What are autoimmune haemolytic anemias?
- Autoimmune haemolytic anaemias (AIHAs) are caused by antibody production by the body against its own red cells!
- They are characterized by a positive direct antiglobulin test (also known as the Coombs’ test)
Classification
- Divided into ‘warm’ and ‘cold’ types according to whether the antibody reacts more strongly with red cells at 37°C or 4°C!
Table 6.5 Immune haemolytic anaemias: classification.
CLL, chronic lymphocytic leukaemia; SLE, systemic lupus erythematosus.
Warm autoimmune haemolytic anemias
Definition
- Most common form of autoimmune hemolytic anemia
- Autoantibodies generated by the body are active only at body temperatures of 37 degrees Celsius or higher and attach to and prematurely destroy red blood cells!
Etiology
- Idiopathic
- Viral (childhood, HIV)
- Autoimmune disease (SLE, RA, scleroderma, UC)
- Malignancies
- Drug induced
Pathogenesis
- Red cells are coated with immunoglobulin (usually IgG) and are therefore taken up by RE macrophages which have receptors for the Ig Fc fragment!
- Part of the coated membrane is lost so the cell becomes progressively more spherical to maintain the same volume and is ultimately prematurely destroyed (in spleen)
Clinical features
- May occur at any age, in either sex!
- Presents as a haemolytic anaemia of varying severity
- Splenomegaly is often seen
- May occur in association with other diseases
- Fatigue
- Weakness
- Dyspnea
- Pallor
- Dizziness
- Palpitations
- SOB
Laboratory findings
- Haematological and biochemical findings are typical of an
extravascular haemolytic anaemia:
- Spherocytosis
- Severe anemia
- Increased MCV
- Hyperbilirubinemia (indirect)
- Reticulocytosis
- LDH elevated
- Decreased haptoglobin
- DAT is positive as a result of IgG, IgG and complement or IgA on the cells
- Best detected at 37 degrees!
Treatment
- Blood transfusion is contraindicated!!
- Remove the underlying cause (e.g. methyldopa).
- Corticosteroids
- Prednisolone is the usual first-line treatment (1mg/kg/day)
- Response is seen within 5 days, 60-70% have remission by 3 weeks
- Dexamethasone
- Monoclonal antibody
- Maptera
- Splenectomy (if fail to respond well to therapy)
- Immunosuppression
- Cyclophosphamide
- Treat underlying disease
- Folic acid in severe cases
- High dose immunoglobulin
- 70-80g
- Given in severe/life threatening hemolysis!