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Haemolytic Anaemia

Clinical features:

  • Anaemia

  • Splenomegaly - Spleen filled with destroyed RBCs

  • Jaundice - Due to increased Bilirubin

  • Pigmented Gallstones - Due to increased Bilirubin


Classification:

  • Hereditary or Acquired

  • Intravascular or Extravascular (liver/spleen)

  • Autoimmune (Coombs +ve) or Non-autoimmune (Coombs -ve)


Hereditary causes:

  • Sickle cell

  • Thalassaemia

  • Hereditary Spherocytosis (Membrane disorder)

  • G6PD Deficiency


Acquired causes:

  • Autoimmune haemolytic anaemia/AIHA (Warm, Cold, Drug-induced)

  • Non-autoimmune haemolytic anaemia (Transfusion reactions, Haemolytic Disease of Newborn)

  • Microangiopathic Haemolysis (MAHA)

  • Paroxysmal Nocturnal Haemoglobinuria (PNH)

  • Metallic heart valve - sheer stress causes haemolysis


Haemolytic Screen

  • FBC - Normocytic anaemia

  • Blood film - Spherocytes/Schistocytes (RBC fragments)

  • LDH - Raised due to cell turnover

  • Reticulocytes - Raised as bone marrow tries to compensate

  • Bilirubin - Raised


N.B. Increased Reticulocytes + Bilirubin is an indicator of Haemolysis.


  • Haptoglobin - Decreased in intravascular haemolysis as it’s used to bind to the Hb


N.B. Main way to differentiate between Intravascular and Extravascular haemolysis


  • DAT/Coombs Test - +ve in autoimmune type.

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Algorithm for the main causes in positive direct antiglobulin test (DAT, or direct Coombs test) © Mikael Häggström, MD CC0 1.0 (https://commons.wikimedia.org/wiki/File:Algorithm_in_positive_direct_antiglobulin_test_(DAT,_or_direct_Coombs_test).png)

Autoimmune Haemolytic Anaemia (AIHA)

Diagnosed by a +ve DAT/Coombs test (shows agglutination). The 2 types of it are based on the temperature at which its autoantibodies function to cause RBC destruction:

  • Warm - IgG-mediated, in which the spleen tags cells for splenic phagocytosis (extravascular)

    • Managed with transfusions, steroids, rituximab, splenectomy

  • Cold - IgM-mediated, in which complement is bound for RBC destruction (intravascular)

    • Often triggered by a Viral infection (occurs 2-3 wks after)


Microangiopathic Haemolytic Anaemia (MAHA)

  • Intravascular haemolytic disorder - Structural abnormalities of small blood vessels causing mechanical RBC destruction, leading to the formation of Schistocytes (cell fragments)

  • Can be primary, but usually secondary to an underlying condition e.g. HUS, TTP, or DIC


Paroxysmal Nocturnal Haemoglobinuria (PNH)

  • Rare acquired stem cell disorder where an abnormal surface glycoprotein on RBCs marks them for complement-mediated haemolysis



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