1- haemolysis

Question 1

what is haemolysis?

Answer 1

premature destruction of circulating red cells (shortened red cells survival)

Question 2

what is compensated haemolysis?

Answer 2

when body responds to increased red cell destruction by also increasing red cell production so not necessarily anaemic as body might meet demand

Question 2

what are the signs of increased red cell production?

Answer 2

erythroid hyperplasia in bone marrow and lots of reticulocytes (big & purple)

*remember this isn’t sign of haemolysis alone - could be mass bleeding etc

Question 2

what are the signs of increased red cell destruction, extravascular?

Answer 2

extravascular = red cells broken down in normal pathway so in spleen or macrophages out of circulation.

causes splenomegaly or hepatomegaly.

products reused normally but excess bilirubin so present jaundiced (excess unconjugated), rest LFTs normal

Question 2

what are the signs of increased red cell destruction, intravascular?

Answer 2

intravascular = broken up outside macrophage just in blood vessels.
bad as Hb can be toxic and clog up kidneys and cause coagulopathies etc.

presents
1. haemoglobinaemia = free Hb in circulation
2. methaemalbuminaemia = Hb mopped up by albumin
3. haemoglobinuria = free Hb in urine, pink turns black (as oxidises in urine)
4. haemosiderinuria = iron stored up makes haemosiderin in RBC, when explode, haemosiderin released in urine

Question 3

what are causes of intravascular haemolysis?

Answer 3

• incompatible blood transfusion
• mechanical RBC trauma like marching trauma from activity
• G6PD deficiency if severe (since they can’t protect themselves form oxidative stress damage)
• damages aortic valve, can make blood turbulent & mechanical rupture to RBC

Question 4

what investigations should be done if suspect haemolysis?

Answer 4

1. blood count & blood film
2. reticulocyte count (raised)
3. serum unconjugated bilirubin (raised)
4. serum haptoglobins (bind free Hb so low)
5. urinary urobilinogen (raised)
6. lactate dehydrogenase (raised) - non specific

*can also do general exam, find out fam history, organomegaly etc

Question 5

what are the causes of haemolysis? (5 main causes)

Answer 5

1. immune (autoimmune & alloimmune)
2. mechanical red cell destruction
3. membrane defects
4. abnormal red cell metabolism
5. abnormal haemoglobin

Question 6

what is meant by autoimmune and alloimmune causes of haemolysis?

Answer 6

autoimmune = when your own antibodies attack your own RBCs

alloimmune = when you make antibodies against someone else’s RBC’s that you’ve now got (either from birth or transfusion)

Question 7

what are the causes of IgG (warm) and IgM (cold) autoantibodies?

Answer 7

these are the types of autoimmune attacking RBCs

IgG is caused by either idiopathic, autoimmune like SLE, drugs, infections

IgM is caused by either idiopathic, infections (EBV), lymphoproliferative disorders

Question 8

what are causes of mechanical destruction of RBCs haemolysis?

Answer 8

• march haemoglobinuria
• damaged heart valve
• damaged microcirculation = severe burns, microangiopathic haemolysis (fibrin strands deposited in small vessels)

Question 9

what are causes of membrane problems causing haemolysis?

Answer 9

acquired membrane problems like liver disease or PNH (paroxysmal nocturnal haemoglobinuria)

genetic membrane problems like hereditary spherocytosis, mutation in one of membrane proteins

Question 10

what is the cause of abnormal red cell metabolism causing haemolysis?

Answer 10

G6PD deficiency = means abnormal red cell metabolism so free radicals build and destroy cell

*usually x-linked so more in males

Question 11

what are causes of abnormal haemoglobin structure making haemolysis?

Answer 11

mutation in haemoglobin chain e.g. sickle cell