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Y3 immunology and haematology > red cells 1 > Flashcards

red cells 1 Flashcards

1
Q

what is anaemia

A

reduction in red cells or their Hb content

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2
Q

what are the causes of anaemia

A

blood loss
increased destruction
lack of production
defective production

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3
Q

what substances are required for red cell production

A

iron, copper, cobalt, manganese

B12, folic acid, thiamine, vit B6, C, E

amino acids

erythropoietin, GM-CSF, androgens, thyroxine

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4
Q

production of RBC

A

pluripotent stem cell under the influence or erythropoeitin then develop into RBC

eject nucleus just before leaving bone marrow

reticulocyte is the step just before a mature RBC

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5
Q

where does RBC breakdown occur

A

reticuloendothelial system

- macrophages in spleen, liver, lymph nodes, lungs etc

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6
Q

what is the normal life span of a RBC

A

120 days

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7
Q

what are RBC recycled into

A

globin –> amino acids –> reutilised

haem

  • iron recycled into haemoglobin
  • haam –> biliverdin –> bilirubin –> bound to albumin in plasma

bilirubin from RBC breakdown before it gets to liver - unconjugated

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8
Q

what is an erythrocyte

what is it made up of

A

mature RBC

membrane
enzymes
haemoglobin

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9
Q

where can genetic defects in congenital anaemia occur

what do they cause

prevalence

A

defects in cell membrane, metabolic pathways, Hb

most reduce RBC survival, result in haemolysis

carrier states are often silent, prevalence varies geographically

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10
Q

red cell membrane

A

skeletal proteins are reponsible for maintaining red cell shape and deformability - spectrin and ankyrin

defects can lead to increased red cell destruction

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11
Q

what is the commonest inherited membrane disorder

A

hereditary spherocytosis

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12
Q

what condition is this

A

hereditary spherocytosis

instead of biconcave shape, defect in skeletal protein leads to loss in structure and cells are sphere shaped

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13
Q

hereditary spherocytosis - dominant or recessive

A

most common forms are autosomal dominant

strong FHx

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14
Q

hereditary spherocytosis - protein defects

A

defects in 5 different structural proteins

ankyrin 
alpha spectrin 
beta spectrin
band 3
protein 4.2

all lead to spherocytes

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15
Q

what happens to the cells in hereditary spherocytosis as a result of their changed shape

A

red cells are spherical

recognised by the body as foreign

removed from circulation by RE system (extravascular - broken down outside the blood vessels)

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16
Q

clinical presentation of hereditary spherocytosis

A

anaemia - red cells aren’t lasting as long

jaundice (neonatal)

splenomegaly - working more than normal

pigment gallstones - bilirubin in plasma is increased so more likely to crystallise in gallbladder

can be an incidental finding w/ very mild symptoms

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17
Q

treatment of hereditary spherocytosis

A

folic acid - increased requirements

tranfusion

splenectomy - if anaemia very severe; reduces red cell destruction

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18
Q

3 other rare membrane disordes

A

hereditary elliptocytosis

hereditary pyropoikilocytosis

south east asian ovalocytosis

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19
Q

what condition is this

A

hereditary elliptocytosis

less severe than spherocytosis but similar symptoms

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20
Q

what condition is this

A

hereditary pyropoikilocytosis

combination of different proteins involved

can become severley anaemic

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21
Q

how does south east asian ovalocytosis present

A

strange, large looking oval red cells

mild clinical picture

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22
Q

what is the function of glycolysis

A

provides energy

pathway interacts with the pentose phosphate shunt

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23
Q

what is the function of the pentose phosphate shunt

A

protects from oxidative damage

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24
Q

important link between pentose phosphate shunt and glycolytic pathway

A

glycose 6 - phosphate dehydrogenase

key to red cell survival

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25
where can enzyme deficiencies occur
glucose 6 phosphate dehydrogenase - affects both pathways pyruvate kinase - rarer, only affects glycolytic pathway
26
function of G6PD
protects red cell proteins (Hb) from oxidative damage produces NADPH - vital for reduction of glutathione reduced glutathione scavenges and detoxifies reactive oxygen species
27
G6PD deficiency - how common - what happens to cells - protection?
commonest disease causing enzymopathy in the world - many genetic variants cells vulnerable to oxidative damage confers protection against malaria - most common in malarial areas
28
inheritance of G6PD deficiency
X linked - affects males - female carriers
29
what condition is this
G6PD deficiency blister cells - top (pooling of Hb) bite cells
30
clinical presentation of G6PD deficiency
variable variable degrees of anaemia neonatal jaundice splenomegaly pigment gallstones drug, broad/fava bean or infection (increases free oxygen species) precipitated jaundice and anaemia: - intravascular haemolysis - toxins are in the circulation w/ cells - haemoglobinuria
31
triggers to haemolysis in G6PD deficiency
infection acute illness e.g. DKA broad (fava) beans drugs - lots
32
what drugs can trigger haemolysis in G6PD deficiency | - don't need to know for exam
antimalarials - primaquine, pamaquine sulphonamides and sulphones - salazopyrin, dapsone, septrin antibacterials - nitrofurantoin analgesics - aspirin antihelminthics - B-naphthol misc - vit K analogues, probenecid, methylene blue
33
pyruvate kinase deficiency | - effects on cells
reduced ATP increased 2,3-DPG cells rigid
34
clinical presentation of pyruvate kinase deficiency
very rare variable severity: anaemia jaundice gallstones can lead to haemolysis
35
what is the structure of Hb
2 alpha chains 2 beta chains 4 associated heme molecules - iron surrounded by protoporphyrin ring
36
what is the function of Hb
oxygen binding and unloading changes binding structure when doing this
37
Hb and gas exchange
O2 to tissues | CO2 to lungs
38
oxygen dissociation curve what is the Bohr effect HbF
shifts as a compensatory mechanism Bohr effect: - acidosis - hyperthermia - hypercapnia HbF - higher O2 affinity than HbA
39
describe normal adult Hb
composed of haem molecule and 2 alpha chains (4 alpha genes, Chr 16), 2 beta genes (2 beta genes, Chr 11) over the first 6 mths of life the gene expression changes, HbF levels drop
40
what are haemoglobinopathies
inherited abnormalities of Hb synthesis reduced/absent globin chain production - thalassaemia (alpha, beta, delta, gamma) mutations leading to structurally abnormal globin chain (HbS - sickle cell, HbC, HbD, HbE, HbO Arab...)
41
areas with high prevalence of haemoglobinopathies
can occur in any ethnic group concentrated in areas where malaria is/was endemic usually because being a carrier allows some level of protection against malaria
42
inheritance of haemoglobinopathies
nearly all are autosomal recessive 2 asymptomatic carriers - 1/4 chance of having affected child, 1/2 change of being carrier/trait
43
Hb structure in sickle cell disease
``` 2 normal alpha chains 2 beta (sickle chains) - point mutation ``` when the cell goes through hypoxic tissues it becomes sickle shaped as the abnormal Hb polymerises - rigid polymers irreversibly form rigid shapes
44
what condition is this
sickle cell (HbSS)
45
pathophysiology of sickle cell
1. Hb S polymerisation 2. vaso-occlusion 3. endothelial dysfunction 4. sterile inflammation
46
inheritance of sickle cell disorder
autosomal recessive one of the commonest inherited disorders worldwide
47
clinical presentation of sickle cell disease
- painful vaso-occlusive crises: bone - chest crisis - hypoxia - more sickling - endless cycle - stroke - SCD is one of the biggest causes of stroke in children - increased infection risk - hyposplenism - chronic haemolytic anaemia - gallstones, aplastic crisis - sequestration crises - spleen, liver
48
what is an aplastic crisis
can occur when erythrovirus infects RBCs, switches of RBC production Aplastic crisis is defined as a decrease in Hb of 3g/dl or more with reticulocytopenia, usually resulting from parvovirus B19 infection
49
management of sickle cell - painful crisis
severe pain - often requires opiates (should be given within 30mins of presentation, effective analgesia by 1hr), avoid pethidine hydration oxygen consider abx
50
life long prophylaxis in sickle cell disease
due to lack of splenic function vaccination penicillin (and malarial) prophylaxis folic acid - long term increased requirements
51
management of acute events in sickle cell diseae
``` hydration oxygenation prompt treatment of infection analgesia - opiates, NSAIDs blood transfusion if very anaemic ```
52
long term management for sickle cell disease
blood transfusion - mainstay of management - episodic/chronic - complications: alloimmunisation, iron overload disease modifying drugs - hydroxycarbamide (increases HbF, works well for painful crises) bone marrow transplantation gene therapy
53
what is alloimmunisation
develop alloantibodies against tranfused blood
54
Hb structure in thalassaemias
reduced or absent globin chain production mutations/deletions in alpha genes (alpha thalassaemia) αα/αα -α/αα = α+ --/αα = α0 - incompatible with life in beta genes (beta thalassaemia) chain imbalance - chronic haemolysis and anaemia
55
spectrum of clinical severity in thalassaemia
homozygous alpha zero thalassaemia - no alpha chains, hydrops fetalis (incompatible with life) beta thalassaemia major (homozygous beta thalassaemia) - no beta chains, transfusion dependent anaemia non-transfusion dependent thalassaemia - 'intermedia' - range of genotypes (HbE/beta thal, HbH disease) thalassaemia minor (common) - carrier state, hypochromic microcytic red cell indices
56
features of beta thalassaemia major
severe anaemia - present at 3-6m/o (switch between HbF and HbA) - expansion of ineffective bone marrow - bony deformities - splenomegaly - growth retardation life expectancy untreated/w/ irregular transfusions - <10yrs
57
what condition is this
beta thalassaemia major no normal looking RBCs nucleated RBCs also present in circulation
58
what is seen here and what condition is it associated with
skeletal expansion in the skull white line = normal boundary of skull hair on end appearance due to bone marrow expansion beta thalassaemia major
59
treatment for beta thalassaemia major - transfusion
chronic transfusion support - 4-6wkly normal growth and development BUT - be aware of iron overloading death in 2nd-3rd decades due to heart/liver/endocrine failure if iron loading untreated
60
treatment for beta thalassaemia major - iron chelation therapy
``` s/c desferrioxamine infusions (desferal) oral deferasirox (exjade) ``` good adherence to chelation - life expectancy near normal - requires regular monitoring - ferritin and MRI scans
61
what can be a cure for beta thalassaemia major
bone marrow transplantation
62
rare defects in haem synthesis
defects in mitochondrial steps of haem synthesis --> sideroblastic anaemia - ALA synthesis mutations - hereditary - acquired (most common) - form of myelodysplasia defects in cytoplasmic steps result in porphyrias

Y3 immunology and haematology (20 decks)

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