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Haematology > Red Cells 1 > Flashcards

Red Cells 1 Flashcards

1
Q

What is anaemia?

A

Reduction in the number of blood cells or the haemoglobin content of the blood cells

Not a pathology itself but rather a result of something elsse (increased production / destruction, Blood loss)

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2
Q

Which metals are required for red cell production?

A

IRON

Copper
Cobalt
manganese

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3
Q

Which vitamins are required for red cell production?

A

B12
FOLIC ACID

Thiamine
Vitamin B6, C, E

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4
Q

Which hormones are required for red cell production?

A

ERYTHROPOIETIN

GM-CSF
Androgens
Thyroxine

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5
Q

Which physiological system is responsible for red cell breakdown? What is this system composed of?

A

Reticuloendothelial system

Composed of macrophages in the spleen*, liver, lymph nodes, lungs etc.

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6
Q

Describe the metabolism of red blood cells that have reached senescence

A

Amino acids from globin protein are reutilized

Iron is reutilized and reincorporated into haemoglobin

Haem is converted into unconjugated bilirubin which binds albumin in the plasma

Bilirubin is then conjugated by the liver and excreted in the urine

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7
Q

How does the type of bilirubin found in the plasma indicate different pathologies?

A

Excess unconjugated bilirubin - excess RBC breakdown

Conjugated bilirubin - hepatic pathology

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8
Q

What are the advantages to the biconcave shape of red blood cells?

A

Maximum surface area for oxygen exchange

Provides a squeezability and flexibility to the cell that allows RBCs to get through tight spaces

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9
Q

Which parts of the red cell are commonly affected by genetic abnormalities? What effect does this tend to have?

A

Red cell membrane
Metabolic pathways within the red cell
Haemoglobin

Tend to result in haemolysis

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10
Q

What is hereditary spherocytosis? How are the mutations transmitted?

A

A disroder in which there is a mutation in one of the genes coding for the cytoskeleton of red blood cells

Results in loss of bi-concave shape and cell becomes spherical

Transmitted in an autosomal dominant pattern

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11
Q

Other than the inefficient shape of the RBCs in hereditary spherocytosis, what effect does the mutation have?

A

Red cells are recognized by the reticuloendothelial system as being abnormal and so are removed from circulation much sooner

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12
Q

How does hereditary spherocytosis tend to present?

A

Varying severity - severity depends on the specific cytoskeleton protein mutation

  • Anaemia (early or late onset)
  • Jaundice (may be neonatal, or unnoticable)
  • Splenomegaly
  • Pigment gallstones
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13
Q

How is hereditary spherocytosis treated?

A
  • Mild cases: folic acid supplementation
  • Moderate cases: blood transfusions
  • Severe cases: splenectomy (removing spleen slows removal of abnormal RBCs from circulation
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14
Q

What are some examples of other RBC membrane disorders?

A
  • Hereditary Elliptocytosis
  • Hereditary Pyropoikilocytosis
  • South East Asian Ovalocytosis
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15
Q

What is the most common disorder of red blood cell enzymatic metabolism?

A

Deficiency in Glucose 6 Phosphate Dehydrogenase (G6PD)

Enzyme functions to protect red cell proteins (haemoglobin from oxidative damage)

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16
Q

How is G6PD deficiency transmitted? What accounts for the high prevalence of the mutation?

A

X linked - affects males, females are carriers

The mutation confers a protection against malaria and so is a survival advantage in areas where malaria is endemic

17
Q

How does G6PD deficiency tend to present?

A
  • Anaemia
  • Jaundice (may be neonatal)
  • Splenomegaly
  • Pigment gallstones
  • Intravascular haemolysis

Varying presentations, some people may only show signs when exposed to oxidative factors such as drugs / infections

18
Q

What is pyruvate kinase deficiency? What is the effect of it? How does it present?

A

Mutation in the pyruvate kinase gene in glycolytic pathway of RBCs, causes reduced ATP and buildup of metabolites, especially 2,3 DPG

2,3 DPG makes cells rigid

  • Anaemia
  • jaundice
  • Gallstones
19
Q

Describe the structure of haemoglobin. When does the structure chamnge?

A

4 protein subunits each with their own haem and iron group

In relaxed position it binds oxygen via the haem group

When bound by 2,3 DPG the protein changes shape and releases the oxygen to the target tissue

20
Q

What are some important factors that influence the affinity of haemoglobin for oxygen?

A

pH - more acidic condition lower affinity. When at tissues that have been active acid is produced and haemoglobin lets go of oxygen to provide it to cells that need it

DPG conc. - Low DPG means lower affinity for oxygen. DPG binding causes release of oxygen, therefore higher DPG means less oxygen binding

Temperature - higher temperature means lower oxygen affinity, probably to do with protein structural integrity

21
Q

Which protein chains make up haemoglobin?

A

Alpha component:
- Made up of 2 alpha chains encoded by 4 alpha genes

Beta component:
- 2 beta chains encoded by 2 beta genes

Beta component can be replaced by gamma or delta genes, encodes different types of haemoglobin

HbA (aabb) - 97% of Hb
Hb A2 (aadd) - 2% of Hb
HbF (aagg) - 1% of Hb

22
Q

What are haemoglobinopathies? What are the different types?

A

inherited abnormalities of haemoglobin synthesis (abnormal haemoglobin)

Thalassaemia - reduced or absent globin chain production. (eg. alpha chain thalassaemia = alpha thalassaemia)

Mutations leading to structurally abnormal haemoglobin chains (eg HbS - sickle cell)

23
Q

Where do haemoglobinopathies tend to be more common?

A

In areas where malaria is or was endemic

Sickle cell - Africa
Thalassaemia - central belt around equator ish

24
Q

Who confers the benefit of haemoglobinopathies in as far as malaria resistance is concerned?

A

Carriers of the recessive allele

  • those who are affected do not benefit
  • carriers don’t suffer the disease but are protected against malaria
25
Q

Describe the pathophysiology of sickle cell disease

A

Mutation in beta chain, causes cells to become deformed into a sickle shape when deoxygenated. Can damage microvasculature

Damage to microvasculature causes inflammation which can cause coagulation and dysregulation of vasomotor tone by vasodilator mediators

All ends up in occluded vessels (vaso-occlusion)

26
Q

How does sickle cell anaemia tend to present?

A

Often precipitayed by sickling mediator eg. infection

  • Bone pain
  • Hypoxia
  • Stroke
  • Hyposplenism (increases risk of infection)
  • Gallstones
  • Aplastic crisis
  • Sequestration crises
27
Q

How are flare ups of sickle cell anaemia treated?

A 
Opiates for pain management 
Hydration
Oxygen 
Antibiotics if infection
Blood Transfusion
28
Q

How is sickle cell anaemia treated long term?

A
  • Vaccination (hyposplenism)
  • Penicillin and malarial prophylaxis
  • Folic acid
  • Hydroxycarbamide (increases foetal haemoglobin and stops sickling)
  • Bone marrow transplantation
29
Q

What is the prognosis for homozygous alpha zero thalassaemia?

A

Not compatible with life

If you have no alpha genes you cannot synthesize haemoglobin and won’t survive

30
Q

What is the prognosis for homozygous beta thalassaemia? (beta thalassaemia major)

A

Can’t make beta chains, but due to gamma and delta chains still synthesize a small amount of haemoglobin

Will rely on transfusions for life but will survive

If irregular transfusions / untreated life expectancy is <10 years

31
Q

What is non-transfusion dependent thalassaemia?

A

Range of different genotypes, but generally thalassaemia that is not dependent on trnasfusions to survive

32
Q

What is thalassaemia minor? How does it present?

A

Missing part of a chain coding gene / one copy of a chain coding gene

Mild anaemia (with small red cells on microscopy)

33
Q

How does homozygous beta zero thalassaemia present? (beta thalassaemia major)

A

Present at 3-6 months because foetal Hb is sufficient in early life, but when become dependent on beta genes that are mutated become anaemic

  • Anaemia
  • Expansion of ineffective bone marrow
  • Bony deformities
  • Splenomegaly
  • Growth retardation
34
Q

How is beta thalassaemia major treated?

A
  • Blood transfusions every 4-6 weeks for life
  • Iron chelation therapy due to iron overloading from repeat transfusions
    • oral deferasirox or desferrioxamine infusions

Bone marrow transplantation is curative

35
Q

What is sideroblastic anaemia?

A

Anaemia due to defects in mitochondrial steps of haem synthesis

Very rare

Haematology (15 decks)

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