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haematology > haemolysis > Flashcards

haemolysis Flashcards

1
Q

haemolysis

A

premature red cell destruction - shortened red cell survival

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2
Q

why are red cells particularly susceptible to damage? (haemolysis)

A
  1. they need to have a biconcave shape to transit circulation successfully
  2. they have limited metabilic reserve + rely exclusively on glucose metabolism for energy
  3. cant generate new protein once in circular - no nucleus
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3
Q

compensated vs decompensated haemolysis

A

compensated = increased red cell destruction compensated by increased red cell production (Hb maintained)

decompensated = increased rate of red cell destruction exceeding bone marrow capacity for red cell production - Hb falls

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4
Q

physiological consequences of haemolysis

A

erythroid hyperplasia - increased bone marrow red cell production

excess red cell breakdown product - eg bilirubin
–> clinical feature differ by aetiology + site of red cell breakdown

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5
Q

bone marrow response to haemolysis

A

reticulocytosis - bluer + bigger on stain, polychromasia

erythroid hyperplasia

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6
Q

classification of haemolysis

A

by site
- intravascular
- extravascular

by cause
- hereditary - membrane, metabolism, haemoglobinopathis
- acquired - immune vs nonimmune causes

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7
Q

causes of hereditary haemolytic anaemias

A

membrane -> hereditary spherocytosis

metabolism -> G6PD deficiency

haemoglobinopathies -> sickle cell, thalassaemia

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8
Q

acquired immune causes of haemolytic anaemia

A

(Coombs positive)

autoimmune -> warm/cold antibody type

alloimmune -> transfusion reaction, haemolytic disease of newborn

drug -> methyldopa, penicillin

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9
Q

acquired NON-immune causes of haemolytic anaemia

A

(Coombs NEGATIVE)

microangiopathic haemolytic anaemia - TTP, HUS(ecoli), DIC, malignancy, preeclampsia
prosthetic heart valves
paroxysmal nocturnal haemoglobinuria
infections - malaria
drug - dapsone

Zieve syndrome - assoc with heavy alcohol, resolves with abstinence

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10
Q

approach to investigation haemolysis

A

confirm haemolytic state
- FBC, reticulocyte count
- serum unconjugated bilirubin
- serum haptoglobins
- urinary urobilinogen

identify cause
- Hx + exam - FH, organomegaly
- blood film

specialist features - Coombs test

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11
Q

blood film features that would suggest cause of haemolysis

A

membrane damage - spherocytes

mechanical damage - red cell fragments

oxidative damage - heinz bodies (G6PD, alpha thalassaemia)

sickle cells

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12
Q

when to suspect haemolysis

A

anaemia with polychromasia -> either acute blood loss or haemolysis

spherocytes

haemosiderin/haemoglobin in urinne - urine dipstick may test pos for but urine microscopy negative for red cells in intravascualr haemolysis

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13
Q

intravascular haemolysis causes

A

mismatch blood transfusion
G6PD deficiency (technically slightly extravascualr too)

red cell frags - heart valves, TTP, DIC, HUS
paroxysmal nocturnal haemoglobinuria
cold autoimmune haemolytic anaemia

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14
Q

extravascular haemolysis causes

A

haemoglobinopathies - sickle cell, thalassaemia
hereditary spherocytosis
haemolytic disease of newborn
warm autoimmune haemolytic anaemia

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15
Q

extravascular haemolysis

A

taken up by reticuloendothelial system (spleen + liver predominantly)
commoner
hyperplasia at site of destruction (splenomegaly +/- hepatomegaly)

release of protoporphyrin
- unconjugated bilirubinaemia - jaundice, gallstones
- urobilinogenuria

normal products in excess

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16
Q

intravascular haemolysis

A

red cells destroyed within the circulation spilling their contents
- haemoglobinaemia/uria - pink urine, turns black on standing

abnormal products in excess
intravascualt haemolysis may be life threatening

17
Q

is there iron deficiency in extravascular / intravascular haemolysis respectively?

A

extra - no

intra - will, will be excreted out

18
Q

what is the usual pathway for energy production for RBC?

A

anaerobic glycolysis

19
Q

folic acid supplementation in rapid haemolysis?

A

yes !!

20
Q

autoimmune haemolysis

A

can be divided into “warm” or cold types according to which temperature the antibodies best cause haemolysis

most commonly idiopathic but may be secondary to a ymphoproliferative disorder, infection or drug

21
Q

warm autoimmune haemolysis

A

IgG
antibody (usually IgG) causes haemolysis best at body temp + haemolysis tends to occur in EXTRAVASCULAR sites -> the spleen

22
Q

causes of warm autoimmune haemolysis

A

idiopathic - commonest
autoimmune disrders (SLE)
lymphoproliferative disorders - lymphoma, CLL
drugs - penicillins, methyldopa
infections

23
Q

management of warm autoimmune haemolysis

A

treatment of underlying disorder

steroids (+/- rituximab)

24
Q

cold autoimmune haemolysis

A

IgM causes haemolysis best at 4degreesC

haemolysis is mediated by COMPLEMENT + is more commonly INTRAVASCULAR

features - raynauds, acrocyanosis
patients respond less well to steroids

25
Q

causes of cold autoimmune haemolysis

A

idiopathic
infections - EBV, mycoplasma
lymphoproliferative disorders - lymphoma

26
Q

general features of haemolytics anaemia

A

anaemia, reticulocytosis
low haptoglobin
raised LDH + indirect bilirubin

blood film features - heinz bodies, spherocytes, fragments, reticulocytes

27
Q

alloimmune haemolysis

A

immune response, antibody produced
(Coombs positive)

haemolytic transfusion reaction
- immediate (IgM predominantly intravascualr
- delayed (IgG) predominantly extravascular

passive transfer of antibody
- haemolytic disease of newborn - RhD, aBO incompatibility, anti-Kell

28
Q

abnormal red cell matabolism causing haemolysis

A

failure to cope with oxidant stress - G6PD deficiency
failure to generate ATP - metabolic processes fail

even metabolic pathways of normal cells if sufficiently stress by dapsone or salazopyrin can get oxidative damage

**Avoid dapsone therapy in G6PD deficiency

29
Q

pathophysio of intravascular haemolysis

A

free haemoglobin is released which then binds to haptoglobin
- as haptoglobin becomes saturated haemoglobin binds to albumin forming methaemalbumin (detected by Schumm’s test)

free Hb is excreted in urine as haemoglobinuria, haemosiderinuria

30
Q

G6PD defieciency

A

commonest red blood cell defect
more common in mediteranean + africa

X-linked recessive
many drugs can precipitate a crisis as well as infections + broad (fava) beans

31
Q

drugs causing haemolysis (in assoc with G6PD def)

A

anti-malarials - primaquine
ciprofloxacin
sulph- group drugs - sulfasalazine, sulfonylureas

32
Q

presentation of G6PD deficiency

A

neonatal jaundice
intravascular haemolysis
gall stones
splenomegaly

**heinz bodies on blood film
bite + blister cells may also be seen

33
Q

G6PD investigations

A

using G6PD enzyme assay
- levels should be checked 3 months after an acute episode of haemolysis
- RBCs with most severely reduced G6PD activity will have haemolysed -> reduced G6PD activity -> not be measure in assay -> false neg results

34
Q

G6PD def vs hereditary spherocytosis

A

SAME presentations - neonatal jaundice, gall stones, infection/drugs precipitate

G6PD
- male only - xlinked recess
- african/med
- heinz bodies
- Ix - enzyme activity of g6pd

hered sphero
- male + female - auto dominant
- northern europe
- spherocytes
- Ix = EMA binding

haematology (21 decks)

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