Haemolysis

Question 1

why are red cells particularly susceptible to damage

Answer 1

• they need a biconcave shape to get round the circulation
• they have limited metabolic reserve and rely on glucose metabolism (no mitochondria)
• cant generate new proteins once in the circulation (no nucleus)

Question 2

what is compensated haemolysis

Answer 2

when there is increased red cell destruction which is balanced out by increased production in the bone marrow

Hb is maintained

Question 3

what is haemolytic anaemia (decompensated haemolysis)

Answer 3

increased rate of red cell destruction exceeding bone marrow capacity for red cell production

Hb falls

Question 4

what are the consequences of haemolysis

Answer 4

erythroid hyperplasia
-increased bone marrow red cell production

excess red cell breakdown products eg. bilirubin

Question 5

how do you measure haemolysis

Answer 5

cant measure is directly

need to measure the consequences eg. increased red cell production, and detection of breakdown products

-billirubin

Question 6

what is the bone marrow’s response to hameolysis

Answer 6

Reticulocytosis

Erythroid hyperplasia

Question 7

what are reticulocytes

Answer 7

red cells straight out fo the bone marrow

have no nucleus

larger than RBCs

automated reticulocyte counting is used

Question 8

what are the two main types of haemolysis

Answer 8

extravascular

intravascular

Question 9

what is extravascular haemolysis

Answer 9

most common

red cells taken up by reticuloendothelial system and destroyed in the spleen or liver

hyperplasia of the site of production occurs (splenomegaly +/- hepatomegaly)

release of protoporphyrin
-unconjugated bilrubinaemia (jaundice, gall stones)

-urobilinogenuria

normal products in excess

Question 10

what is intravascular haemolysis

Answer 10

red cells destroyed within the circulation

causes:

haemoglobinaemia (free Hb in circulation)
methaemalbuminaemia (albumin in circulation)
haemoglobinuria (pink urine, turns black on standing)
haemosiderinuria (haemosiderein = iron containing protein in urine)

Question 11

causes of intravascular haemolysis

Answer 11

• ABO incompatible blood transfusion
• G6PD deficiency
• severe falciparum malaria
• rare PNH(paroxysmal nocturnal haemoturia), PCH

Question 12

causes of extravascular haemolysis

Answer 12

all other causes of haemolysis

Question 13

investigations for haemolysis

Answer 13

1 confirm haemolytic state

FBC 
Reticulocyte count 
Serum unconjugated bilirubin
Serum haptoglobins
Urinary urobilinogen 

2. identify cause

history + examination
blood film
specialist investigations (eg. Coombs’ test)

Question 14

how can you classify haemolysis by red cell defect

Answer 14

1. premature destruction
2. abnormal cell membrane
3. abnormal red cell metabolism
4. abnormal haemoglobin

can be congenital or acquired

Question 15

what are the immune causes of haemolysis

Answer 15

autoimmune haemolysis
-antibodies to your own cells

alloimmune haemolysis
-antibodies to foreign red cells

Question 16

what is warm (IgG) autoimmune haemolysis

Answer 16

IgG mediated

idiopathic 
autoimmune disorders 
lymphoproliferative disorders 
drugs (penicillins) 
infections

Question 17

what is cold autoimmune haemolysis

Answer 17

IgM mediated

infections
lymphoproliferative disorders

Question 18

what is direct combo’ test

Answer 18

identifies antibody bound to OWN red cells

Question 19

causes of alloimmune haemolysis

Answer 19

Haemolytic transfusion reaction

• immediate IgM - intravascular
• delayer IgG - extravascular

Passive transfers of antibody

• haemolytic disease of the newborn
• Rh D
• ABO incompatibility

Question 20

causes of acquired haemolysis

Answer 20

Disseminated intravascular coagulation

Haemolytic uraemia syndrome

TTP

Leaking heart valve

infections eg. malaria

Question 21

what acquired membrane defects cause haemolysis

Answer 21

• severe liver disease (Zeeive’s syndrome)
• Vitamin E deficiency
• Proxsysmal nocturnal haemoglobinuria

Question 22

what congenital membrane defects cause haemolysis

Answer 22

reduced membrane deformability

increased transit time through spleen

oxidant environment in spleen causes extravascular red cell destruction

hereditary spherocytosis

Question 23

what red cell metabolism defects cause hameolysis

Answer 23

glucose-6-phosphodehydrogenase deficiency (preventing glycolysis and ATP production for the red cells) so less ATP produced and cant cope with oxidative stress

failure to generate ATP - metabolic processes fail

Question 24

congenital causes of abnormal haemoglobin causing haemolysis

Answer 24

Sickle cell disease -HbS