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Haematology > Haemolysis > Flashcards

Haemolysis Flashcards

1
Q

what is haemolysis

A

Premature red cell destruction

i.e. shortened red cell survival

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2
Q

what is compensated haemolysis

A

increased red cell destruction compensated by increased rbc production = Hb MAINTAINED

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3
Q

what is haemolytic anaemia

A

DECOMPENSATED HAEMOLYSIS
increased rate of red cell destruction exceeding bone marrow capacity for production
= Hb FALLS

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4
Q

what are the physiological consequences of haemolysis

A

erythroid hyperplasia (increased marrow red cell production)

excess rbc breakdown products e.g. bilirubin

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5
Q

what is the bone marrow response to haemolysis

A

reticulocytosis

erythroid hyperplasia

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6
Q

do reticulocytes have nuclei

A

no

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7
Q

what colour are reticulocytes

A

polychromasia (due to ribosomal RNA)

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8
Q

what can reticulocytosis be a result of

A

haemolysis
bleeding
iron therapy in iron deficiency anaemia

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9
Q

what stain for RNA in reticulocytes

A

supravital new methyl blue

Automated reticulocyte counting:
Ribosomal RNA is labelled with a fluorochrome and fluorescent cells are counted

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10
Q

what is extravascular haemolysis

A

when rbcs are Taken up by reticuloendothelial system (spleen and liver predominantly)

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11
Q

what is intravasuclar haemolysis

A

when red cells are destroyed within the circulation

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12
Q

which is the more common type of haemolysis

A

extravascular

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13
Q

what happens at site of destruction in extravascualr haemolysis

A

hyperplasia= splenomegaly +/- hepatomegaly

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14
Q

what is released in extravascular haemolysis

A

protoporphyrin:

  • unconjugated bilirubinaemia = jaundice + gallstones
  • urobilinogenuria

(normal products but in excess)

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15
Q

what is released in intravascular haemolysis

A

Red cells are destroyed in the circulation spilling their contents. This explains the pathophysiology:

Haemoglobinaemia (free Hb in circulation)

Methaemalbuminaemia
(proteolytic breakdown of haemoglobin to form both haem and methaem. Methaem combines with blood plasma albumin to form methemalbumin)

Haemoglobinuria: pink urine, turns black on standing

Haemosiderinuria

(ABNORMAL products)

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16
Q

is intra or extra vascular haemolysis life threatening

A

intra (abnormal products in blood stream)

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17
Q

what can cause intravascular haemolysis

A 
ABO incompatible blood transfusion
G6PD deficiency
Severe falciparum malaria (Blackwater Fever)
HUS
DIC
TTP
Rare: PNH,PCH
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18
Q

what can cause extravascular haemolysis

A

legit every other cause (autoimmune haemolytic anaemia, spherocytosis)

19
Q

what Ix to confirm haemolysis

A 
FBC (+ BLOOD FILM)
Reticulocyte count
Serum unconjugated bilirubin
Serum haptoglobins
Urinary urobilinogen
20
Q

what Ix to identify the cause of haemolysis

A

Hx and exam: genetic/ acquired

blood film: spherocytes, mechanical damage, oxidative stress (heinz bodies), sickle cells

specialist tests: direct coombs etc

21
Q

how can haemolysis be classified by red cell defect

A
  1. premature destruction of normal rbcs (immune/ mechanical)
  2. abnormal cell membrane
  3. abnormal cell metabolism
  4. abnormal haemoglobin
22
Q

is premature destruction of normal red cells a congenital or acquired cause of haemolysis

A

acquired

23
Q

what are the causes of premature destruction of normal red cells

A

immune: autoimmune haemolysis and alloimmune haemolysis
mechanical: DIC, HUS, TTP, leaking heart valve, infections (malaria), burns related

24
Q

what are the types of autoimmune haemolysis

A

(these cause premature destruction of normal red cells)
warm IgG
cold IgM

25
Q

what causes warm autoimmune haemolysis

A 
idiopathic (most common) 
autoimmune disorders (SLE, lymphproliferative disorders, drugs (penicillin), infections
26
Q

what causes cold autoimmune haemolysis

A

idiopathic
infections (EBV, mycoplasma)
lymphoproliferative disorders

27
Q

what does direct coombs test do

A

identifies antibody and compliment bound to own red cells

uses patients RBCs + mouse anti -human IgG

+ve test = agglutination

28
Q

what are the types of alloimmune haemolysis

A

immune response (antibody response)- haemolytic transfusion reaction

passive transfer of antibody- haemolytic disease of the newborn

29
Q

what are types of haemolytic transfusion reactions

A

(both alloimmune, antibody produced)
immediate IgM- predominantly intravascular
delayed IgG- predominantly extravascular

30
Q

what are the types of haemolytic disease of the new born

A

Rh D
ABO incombatability
anti-kell

31
Q

what are the causes of mechanical premature destruction of normal red cells

A 
(these all acquired) 
DIC 
HUS (ecoli 0157)
TTP
leaking heart valve 
infections (malaria)
burns related (sheared as pass through damaged capillaries)
32
Q

what are the acquired causes of abnormal red cell membrane (resulting in haemolysis)

A 
liver disease (zieve syndrome) (
vit E def 
paroxysmal nocturnal haemoglobinuria
33
Q

what are the features of zieves syndrome

A 
haemolysis 
alcoholic liver disease 
hyperlipidaemia 
anaemia 
polychromatic macrocytes 
irregularly contracted cells
34
Q

what are the congenital causes of abnormal red cell membranes (causing haemolysis)

A

hereditary spherocytosis (HS)

35
Q

why does HS cause haemolysis

A

Reduced membrane deformability
Increased transit time through spleen
Oxidant environment in spleen causes extravascular red cell destruction

36
Q

what are the congenital causes of abnormal red cell metabolism (causing haemolysis)

A 
G6PD deficiency (failure to cope with oxidative stress) 
failure to generate ATP (metabolic processes fail)
37
Q

what are the congenital causes of abnormal haemoglobin (causing haemolysis)

A

sickle cell diseases (point mutation in beta globin chain that causes abnormal polymerisation resulting in shortened cell survival)

38
Q

what deformities happen in beta thalassaemia major

A

Bony deformities of chronic erythroid hyperplasia and marrow cavity expansion

39
Q

what inheritance is HS

A

dominant

40
Q

what type of haemolysis does HS causes

A

chronic extravascular (splenomegaly)

41
Q

what type of haemolysis does malaria cause

A

intravascular

42
Q 
diagnose: 
Anaemic 
Hb80-100 supravital stain
Thai girl
Intermittant jaundice when has fever/unwell and oxidant drugs
A

HbH
A form of alpha thalassaemia. 3 of 4 alpha genes are not working so there is an excess of beta chains which can precipitate.
All cells contain some β4 and have a reduced survival as β4 is toxic and precipitates when ox stress.
Reduced red cell survival =haemolysis!!!

43
Q

what are the acquired causes of altered red cell metabolism

A

Dapsone (antibiotic) or salazopyrin (rheumatology) therapy

44
Q

what are the differences in ABO and RhD transfusion reactions

A

ABO= immediate intravascular haemolysis

RhD= delayed extravascular haemolysis

Haematology (27 decks)

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