Haemolysis Flashcards
What is haemolysis?
Premature red cell destruction
i.e. shortened red cell survival
Why are red cells susceptible to damage?
- biconcave shape
- limited metabolic reserve (no mitochondria)
- Can’t generate new proteins as no nucleus
What is meant by a compensated haemolysis?
- Increased red cell destruction compensated by increased red cell production
=> Hb Maintained
When do patients with haemolysis become anaemic?
Rate of red cell destruction > red cell production
=> Hb Falls
What are the main consequences of haemolysis?
Erythroid hyperplasia (+reticulocytosis)
Excess red cell breakdown products eg billirubin
How does reticulocytosis appear on a blood film?
polychromasia
- different coloured cell due to RNA in reticulocytes picking up purple pigment
What is the difference between intravascular and extravascular haemolysis?
Extravascular
- Taken up by reticuloendothelial system (spleen and liver)
Intravascular
- destroyed within the circulation
WHich of extra/intravascular haemolysis is more common?
Extravascular
WHat does extravascular haemolysis cause?
- Hyperplasia at destruction site (hepato/splenomegaly)
- Release of protoporphyrin
- Unconjugated bilrubinaemia
=> Jaundice/ Gall stones /Urobilinogenuria
Normal products, just in excess
What does intravascular haemolysis cause?
- destroyed in the circulation
=> Haemoglobinaemia (free Hb in circulation)
=> Methaemalbuminaemia
=> Haemoglobinuria: pink urine, black on standing
=> Haemosiderinuria
These are Abnormal products
What are the rare cases that intravascular haemolysis does occur?
- ABO incompatible blood transfusion
- G6PD deficiency
- Paroxysmal Noctural Haemoglobinuria (PNH)
How would you investigate a patient with suspected haemolysis?
FBC (+ BLOOD FILM) Reticulocyte count Serum unconjugated bilirubin Serum haptoglobins Urinary urobilinogen
HOw can investigations help us narrow down the cause of haemolysis?
Hx - give indication of Genetics/FHx
Blood Film: Membrane damage (spherocytes)
Mechanical damage - valve replacement
=> (red cell fragments)
Oxidative damage (Heinz bodies)
Others e.g.. HbS (sickle cells)
Specialist investigations (Direct Coombs’ test)
What causes of haemolysis are acquired?
- Premature destruction
- Immune - auto/alloimmune, to own Ab or ones pt has been exposed to previously
- Mechanical - metal heart valve - Abnormal cell membrane
- Liver disease (Zieve’s)
- Vit E deficiency
- PNH
What causes of haemolysis are congenital?
- Abnormal red cell metabolism
- e.g. G6PD deficiency - Abnormal haemoglobin
e. g. sickle cell anaemia
What can cause autoimmune haemolysis?
Warm Ab (IgG)
- Idiopathic (commonest)
- Autoimmune disorders (SLE)
- Lymphoproliferative disorders
- Drugs (penicillins)
- Infections
Cold (IgM)
- Idiopathic
- Infections
- Lymphoproliferative disorders
WHat are the potential causes of Alloimmune haemolysis?
Transfusion reaction
Immediate (IgM) - intravascular
Delayed (IgG) - extravascular
Passive transfer
- Haemolytic disease of the newborn
- Rh D
What else can cause mechanical RBC destruction?
Disseminated intravascular coagulation (DIC)
Haemolytic uraemic syndrome (eg E. coli O157)
Infections e.g. Malaria
What physical signs can become apparent in Beta Thalassemia Major?
Bony deformities due to erythroid hyperplasia
e.g. frontal bossing of skull
- marrow cavity expansion
How would Beta Thalassemia appear on a blood film?
- hypo/micro targets
- nucleated rbc’s
- pappenheimer bodies
A 22 year old female presents with Splenomegaly and Intermittent mild jaundice. She is also troubled by recurrent Gallstones. Her Father had splenectomy in young adulthood for gallstones.
What hereditary disorder could cause this clinical picture, and how is it inherited?
Hereditary Spherocytosis
- chronic extravascular haemolysis
- Dominant inheritance
