Immune haemolytic anaemia
In this group of disorders, RBCs react with autoantibody +/– complement, which leads to their destruction by the reticuloendothelial system. Many drugs can induce antibody-mediated haemolysis, e.g. penicillins, cepha-losporins, ibuprofen, anti-malarials, rifampicin, antihistamines. Mechanisms are variable. Immune haemolytic anaemia can be divided into isoimmune and autoimmune forms.
Sensitization induces maternal red cell antibodies that cross placenta and haemolyse foetal and neonatal red cells. Usually, direct Coombs test +ve.
· Rhesus haemolytic disease.
· ABO incompatability.
· Other blood group incompatibilities, e.g. Kell, Duffy, blood groups.
· Majority are idiopathic.
· Other causes: drugs (e.g. penicillin), lymphoid malignancies, autoimmune diseases (e.g. SLE, IBD).
· Variable haemolytic anaemia, mild jaundice, splenomegaly, DCT +ve.
· Warm autoantibodies—often non-specific.
Give oral prednisone. If no response give rituximab (anti-CD 20 antibody). Consider splenectomy if severe or poorly responsive to immunosuppression.
· Very rare in children except PCH (see Paroxysmal cold haemoglobinuria).
· RBC antibody reacts most actively <32*C to cause intravascular RBC haemolysis.
· Idiopathic or secondary to EBV or Mycoplasma infection.
· Acrocyanosis in cold, splenomegaly.
· Chronic haemolytic anaemia, DCT –ve for IgG, +ve for C3.
· IgM autoantibodies react best at 4*C.
Treatment rarely needed. Warmth, immunosuppression, plasma exchange, and splenectomy may help. Usually, the condition is self-limiting if there is an infectious cause.
· s to infections (varicella, measles, syphilis) and vaccinations.
· Acute onset of intravascular haemolysis, after fever and chills.
· Due to a biphasic antibody, called Donath Landsteiner antibody.
· Antibody fixes on the cells in the cold peripheries and lyses in the central warmth of the body—protect from cold.
Transfuse as required. Condition is self limiting.