Haemolysis Flashcards
What is the definition of haemolysis?
premature red cell destruction
Why are red cells particularly susceptible to damage?
need biconcave shape to transit circulation; limited metabolic reserve and rely on glycloysis; can’t geenrate new proteins in circulation
What is compensated haemolysis?
increased red cell destruction compensated by increased red cell production
What is haemolytic anaemia?
decompensated haemolysis
What are the consequences of haemolysis?
erythroid hyperplasia; excess red cell breakdown products
What is the bone marrow response to haemolysis?
reticulocytosis; erythroid hyperplasia
When else may reticulocytosis be seen?
response to bleeding; iron therapy in IDA
how is automated reticulocyte counting carried otu?
ribosomal RNA is albelled with fluorochrome and fluorescent cells are counted
What is the difference between extravascular and intravascular haemolysis?
extravascular- taken up by reticuloendothelial system (spleen and liver); intravascular- RBCs destroyed within the ciruclation
Is intra or extravascular haemolysis more common?
extravascular
What occurs with extravascular red cell destruction?
hyperplasia at site of destruction; release of protoporphyrin (unconjugated bilirubinaemia and urobilinogenuria
What is seen with intravascular red cell destruction?
haemoglobinaemia; methaemalbuminaemia; haemoglobinuria; haemosiderinuria
What is seen with haemoglobinuria?
pink urine; turns black on standing
What is the difference between the products of intravascualr and extravascular haemolysis?
intra- abnormal products whereas extravascular is normal products in excess
What are the causes of intravascular haemolysis?
ABO incompatibility; G6PD deficiency; severe flaciparum malaria (blackwater fever); PNH; PCH
What is seen on blood film with membrane damage?
spherocytes
Waht is seen on blood film with mechanical damage?
red cell fragmnets
What is seen on blood film with oxidative damage?
Heinz bodies
How else can haemolysis be classified?
by red cell defect: 1- premature destruction of normal RBCs; abnormal cell memrbane; abnormal red cell maetabolism; abnormal Hb
What are the causes of immun mediated haemolysis?
autoimmune haemolysis; alloimmune haemolysis
What are the 2 types of autoimmune haemolysis?
warm and cold
Waht antibodies are seen with warm AI haemolysis?
IgG
What antibody is seen with cold AI haemolysis?
IgM
What are the causes of warm AI haemolysis?
idiopathic; AI (eg SLE); lymphoproliferative disorders (CLL); drugs (penicillins); infections
What are the causes of cold AI haemolysis?
idiopathic; infections (EBV, mycoplasma); lymphoproliferative disorders
What is hte purpose of direct commbs test?
identifies antibody and complement cound to own red cells
What is used in a direct coombs test?
patients RBCs (coated with IgG and complement)and mouse anti-human IgG
What are hte causes of alloimmune haemolysis?
haemolytic transfusion reaction; haemolytic disease of the newborn
What is the difference between the antibodies and haemolysis seen with haemolytic transfusion reactions?
immediate- IgM and intravascular; delayed- IgG and extravascular
What are the causes of mechanical red cell destruction?
DIC; haemolytic uraemic syndrome (E.coli O157); TTP; leaking heart vlave; infection eg malaria
what is microangiopathic haemolytic anaemia?
red cell fragmentation as a result of mechnical damage from damaged endothelial cells
What is seen on blood film with burns related haemolysis?
microspherocytes
What causes burns realted haemolysis?
red cells are sheared as they pass through damaged capillaries- only severe burns
What are the causes of acquired membrane defects?
liver disease e.g Zieve’s syndrome; vitamin E deficiency; paroxysmal nocturnal haemoglobinuria
What is the triad in Zieve’s syndrome?
haemolysis; alcoholic liver disease and hyperlipidaemia;
What is seen on blood film with Zieve’s syndrome?
anaemia; polychromiatic macrocytes; irregularly contracted cells
What is the characteristic sign assocaited with paroxysmal nocturnal haemoglobinuria?
red urine in the morning
What causes PNH?
defective surface proteins on RBC causing a reactio n with the innate immune system
what causes hereditary spherocytosis?
mutation in genes related to membrane proteins that allow cell to change shape
What drugs can cause haemolysis due to disruption of metabolic pathways of normal RBCs?
dapsone; salazopyrin
What is seen on blood film with dapsone therpay?
keratocyte and irregularly contracted cell
What is HbH?
beta4
Why do cells contained beta4 globin chains have reduced survival?
beta4 is toxic and prepitates when oxidative stress
What are Heinz bodies?
red cell inclusions comprised of denatured Hb normally removed by spleen eg in G6PD deficiency
