Haemalytic anaemia

Question 1

normal red cell life span

Answer 1

120 days

Question 2

definition of haemolysis

Answer 2

shortened red cell survival

can be:
* intravascular - within circulation
* extravascular - removal/destruction by reticuloendothelial system (spleen)

inherited/acquired

Question 3

causes of extravascular haemolysis

Answer 3

autoimmune
alloimmune
hereditary spherocytosis

Question 4

causes of intravascular haemolysis

Answer 4

malaria - most common globally (plasmodium falcipium) - in severe forms depicted as black water fever, acute haeloysis -> haemoglobinuria -> anaemia

G6PD deficiency

mismatched Ab transfusion

cold Ab haemolytic syndromes (IgM)

drugs (dapsin)

MAHA damage to endothelium and to red cells as they travel through eg HUS, TTP

paroxysmal nocturnal haemoglobinuria - acquired genetic defect in synthesis of GPIanka - mechanism by which cells attach protein to surface

Question 5

what can hereditory haemolytic anaemias be a defect of

Answer 5

membrane - cytoskeletal proteins, cation permeability

red cell metabolism - require anaerobic glyocysis to make ATP

Hb (most common) - thalassaemia, sickle cell syndrome, unstable Hb varient

Question 6

inheritence of hereditory spherocytosis

Answer 6

autosomal dominant

Question 7

consequences of haemolysis

Answer 7

• anaemia - but bone marrow can compensate sometimes
• erythropid hyperplasia with increased red cell production and circulating reticulocytes
• increased folate demand
• susceptibility to effect parvovirus B19
• propensity to gallstones (increased bilirubin)
• increased risk of iron overload (increased intestinal absorption)/osteoporosis

Question 8

why does haemolysis -> risk from parvovirus b19

Answer 8

parvovirus infect developing erythroid cells in the bone marrow -> arrest maturation
in normal = little impact on Hb
if Hb survival shortened -> parvovirus fall in Hb level

self limiting problem - infection cleared by immune system
might need transfusion
immunity is lifelong

Question 9

cell count in parvovirus

Answer 9

expect bone marrow production switched off -> drop in reticulocyte

aplastic crisis due to parvovirus
low/absent reticulocyte

Question 10

marrow in a person with parvovirus infection

Answer 10

erythroid precursers
arrested at early stage of maturation
they all look similar - no differentiation

Question 11

liver biopsy in pyruvate kinase deficiency - defect in glycolysis

Answer 11

increased iron in the parenchyma of liver and guppfer cells

Question 12

what increases the risk of gallstones in haemolytic anaemia

Answer 12

coinheritance of gilberts disease (where BR conjugation impaired) -> moe unconjugated BR

-> more propensity to get gall stones

Question 13

pathogenesis of gilberts

Answer 13

genetic polymorphism - change in promoter of UGT 1A1 gene -

instead of normal 6TA repeat in TATA box - get extra dinucleotide on each allele -> TA7/TA7 ->

reduction of trasncription of UGT 1A1 -> reduction expression of protein in liver -> less efficient BR conjugation

Question 14

clinical features of haemolytic disorders

Answer 14

pallor - anaemia
jaundice
splenomegaly - when spleen playing role in destruction of RBC (extravascular haemolysis) or extramedullary haemopoiesis
pigmenturia - abnormal colour to urine, haemoglobinuria
FHx- inhertited

Question 15

blood lab features of haemolytic anaemia

Answer 15

• anaemia (not always)
• high reticulocyte - except when parvovirus
• polychromasia - cells take eosinophilic and basophilic dye - blue/pruple colour - correspond to reticulocyte

Question 16

biochemical features of haemolytic anaemia

Answer 16

• hyperbilirubinaemia
• increased LDH - enzyme in the RBC is released into blood stream in intravascular haemolysis
• reduced/absent haptoglobins - in intravascular haemolysis, they bind to Hb - binding capacity is overloaded
• haemoglobinuria
• haemosiderinuria - stain for iron - Pearl stain - detect iron excreted from tubular cells - implies intravascular haemolysis

Question 17

structure of RBC membrane

Answer 17

lipid bilayer - rests on cytoskeletal scaffold made of spectrin

proteins link lipid bilayer to spectrin including:
* band 3 - major anion transporter
* Ankyrin-1
* 4.2
* GPI

Question 18

pathophysiology of paroxysmal nocturnal haemoglobinuria

Answer 18

GPI lacking in paroxysmal nocturnal haemoglobinuria - produced by biosynthesis, highly coinserved mech

for attachment of biomolecules to cell surface including complement regulatory proteins,

protect RBC from damage from complement

**so w/o GPI - red cells are destroyed by complement -> intravascular haemolysis **

Question 19

2 groups of haemolytic anaemia with membrane defects

Answer 19

hereditary spherocytosis
hereditary elliptocytosis

Question 20

where is the defect in hereditary spherocytosis

Answer 20

vertical interaction in membrane between protiens that link bilayer and cytoskeleton
* band 3
* protein 4.2
* ankyrin
* B-spectrin

Question 21

where is the defect in hereditary elliptocytosis

Answer 21

Horizontal interaction
* a spectrin
* b spectrin
* protein 4.1

Question 22

summarise hereditary spherocytosis

Answer 22

most common inherited defect in red cell cytoskeleton
Fhx in 75% - autosomal dominant
25% no FHx - de novo or recessive

RBC have increased sensitivity to lysis in hypotonic saline -> osmotic fragility test

reduced binding of eosin-5-maleimide to RBC surface

Question 23

blood film with hereditary spherocytosis

Answer 23

lack central pallor
smaller
more densly stained
MCHC increased - hyperchromic cells
polychromatic cells - young red cell population

Question 24

test for hereditary spherocytosis

Answer 24

**dye-binding test **
flow cytometry
look at mean cell flurescence with eosin-5-maleimide

reduced flurescence
cut off - 0.8

Question 25

blood film for carrier hereditary elliptocytosis

Answer 25

elliptical/oval appearance no polychromasia normal blood count

Question 26

hereditary pyropoikilocytosis film

Answer 26

homozygous state for hereditary elliptocytosis (heterozygotes barely clinically effected, homozygotes get severe haemolytic anaemia in new born) fragmentation of red cells vesiculation of membrane of red cells poikilocytosis

Question 27

summarise glucose-6-phosphate dehydrogenase deficiency

Answer 27

most common defect in RBC metabolism prevalent where malaria endemic - protection from plasmodium falciparium X linked varity of phenotypes - most severe in hemizygous males nad homozygous females

Question 28

pathogenesis of G6PD deficiency

Answer 28

G6PD catalyses 1st step in pentose phosphate (or hexose monophosphate pathway) involved in glycolysis although this is minor **main function of G6PD - generate NADPH - needed to maintain intracellular levels of glutathione - needed to protect red cell from oxidative stress ** so deficiency -> susceptable to oxidative stress

Question 29

clinical features of G6PD deficiency

Answer 29

Steady state asx neonatal jaundice (world wide most common cause of kernicterus) **acute haemolysis - triggered by oxidants/infection/drugs/fava beans** chronic haemolytic anaemia - rare

Question 30

blood film from G6PD def

Answer 30

contracted cells nucleated RBC bite cells Hb retracted to one side of cell - hemighosts *only seen in acute haemolytic episode* *In steady state - the blood film is unremarkable*

Question 31

blood film for G6PD when stain with methyl violet

Answer 31

peripheal inclusions - Heinz bodies - denatured Hb - characteristic if oxidative haemolysis seen transiently because heinz bodies removed by splene

Question 32

agents that may cause haemolysis in G6PD deficiency

Answer 32

anti-malarials - primaquine abx - sulphonamides, ciprofloxacin, nitrofurantoin dapsone Vit K fava beans - including in mum if breastfeeding mothballs

Question 33

key metaboilic pathway in red cel -> haemolysis

Answer 33

emden-meyerhof pathway nucleotide metabolism glutathione metabolism

Question 34

film for pyruvate kinase deficiency

Answer 34

defect in glycoytic pathway echinocytes - red cell projections. as they shrink - cells look like spherocytes number of echinocytes increase post-splenectomy.

Question 35

film in pyrimidine 5'-nucleotidase deficiency

Answer 35

pyrimidine nucleotides are toxic to RBC - but cell need to salvage purine nucleotides deficiency of this enzyme -> basophilic stippling in red cells

Question 36

features that help dx of haemolytic anaemia

Answer 36

age of onset - if young more likely inherited pattern of haemolysis - episodic (G6PD) /chronic mode of inheritance other somatic defect - some glycolytic disorder associated with neuromuscular disease

Question 37

1st line ix for haemolytic anaemias

Answer 37

* direct antiglobin test - detect Ig on rbc (exclude autoimmune) * urinary haemosiderin/haemoglobin - suggest whether intravascular * LDH and haptoglobin * osmotic fragility or dye binding test * G6PD (acute episodic) +- PK activity (chronic) * hb separation A and F % - electrophesis or high performance liquid chromatography * Heinz body stain * Ham's test/flow cytometry of GPI-linked proteins - for paroxysmal nocturnal haemoglobinuria * thick and thin blood film

Question 38

principles of mx of haemolytic anaemia

Answer 38

* folic acid supplementation * avoid precipitating factors * red cell transfusion/exchange * immunisation against blood borne viruses - eg hep B and A * monitor for chronic complications - gall stones, iron overload, osteoporosis * cholecystectomy for gallstones * splenectomy if indicated

Question 39

conditions to consider for splenectomy

Answer 39

Pyruvate kinase deficiency and some other enzymopathies hereditory spherocytosis severe elliptocytosus/pyropoikilocytosis thalassamia - intermedia immune haemolytic anaemia (now have immune mod drugs to try 1st)

Question 40

complication of splenectomy

Answer 40

risk of sepsis from cepsulated bacteria - pneumococcus, haemophilus, meningococcus - risk reversed by immunisation and penicillin prophylaxis

Question 41

indications of splenctomy

Answer 41

criteria: * transfusion dependence - need iron chelation to prevent iton overload * growth delay * physical limitation when Hb <=80 * hypersplenism -> pooling aggrevating anaemia, additional cytopenia perform between age 3-10yrs to allow development of immunity and then max growth

Question 42

Hb stability test

Answer 42

heat stability and isopropanol precipitation tests positive

Question 43

haemoglobin hammersmith

Answer 43

severe electrophoretically silent Heinz body haemolytic anaemia mutation disrupts haem contact redued oxygen affinity