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Haematology > RBCs 1 - Physiology and Congenital Anaemias > Flashcards

RBCs 1 - Physiology and Congenital Anaemias Flashcards

1
Q

What is anaemia?

What are the aetiologies of anaemia?

A

Reduction in Red Blood Cells, or a reduction in their content.

There are multiple aetiologies of anaemia

  • Blood loss
  • Increased destruction
  • Lack of production
  • Defective production
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2
Q

What substances are required for red cell productio

A

Metals:

  • iron
  • copper
  • cobalt
  • manganese

Vitmains:

  • B12
  • Folic acid
  • Thiamine
  • Vit. B6
  • Vit C
  • Vit E

Amino Acids

Hormones:

  • Erythropoetin
  • GM-CSF
  • Androgens
  • Thyroxine
  • SCF
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3
Q

From what cell do RBC come from?

What is the cell step just prior to erythrocyte in the differentiation of RBC?

A

Pluripotent stem cells

Reticulocyte

(This cell step can be used to look at RBC formation).

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4
Q

Where are RBCs broken down?

What happens to the constituent parts of the cell?

A
  • RBC’s are broken down in the reticuloendothelial system
    • By macrophages in the Spleen, Liver, Lymph Nodes, Lungs etc

The haemoglobin is broken down:

  • Globin is reutilised
  • Haem is converted to Bilirubin

This bilirubin is bound to albumin in the plasma (and is unconjugated).

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5
Q

What are the 3 key components of the Erythrocyte that are liable to abnormal changes and subsequently anaemia?

A
  • Membrane
  • Enzymes
  • Haemoglobin
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6
Q

Outline generally how congenital anaemias impact the RBC?

What does this often result in the RBC?

A

Genetic defects described

  • In red cell membrane
  • In metabolic pathways (enzymes)
  • In haemoglobin

Resulting in reduced red cell survival (increased haemolysis)

(Remeber that due to the genetic side of these disease there is often carrier states that are silnet, and geographical variation is an important factor too).

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7
Q

What is the importance of skeletal proteins in the RBC?

Defects in these proteins result in what?

A
  • Skeletal proteins are responsible for maintaining red cell shape and deformability
  • Defective skeletal proteins can lead to increased cell destruction (haemolysis)
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8
Q

What is Hereditary Spherocytosis?

A

A hereditary condition caused by defects in the following 5 structural proteins:

  • Ankyrin
  • Alpha Spectrin
  • Beta Spectrin
  • Band 3
  • Protein 4.2
    • Probs don’t learn these.

Resulting in spherical RBCs, which are removed from the circulation by the reticuloendothelial cell.

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9
Q

What is the clinical presentation of Hereditary Spherocytosis?

A
  • Anaemia
  • Jaundice (particularly in the neonate*)
  • Splenomegaly
  • Pigment gallstones

*Jaundice occurs because RBCs are broken down v. fast - with a build-up of bilirubin, particularly in v. young as they aren’t good at getting rid of excess bilirubin quickly*

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10
Q

What is the treatment of Hereditary Spherocytosis?

A
  • Folic Acid (increased requirements)
  • Transfusion
  • Splenectomy
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11
Q

Why do red cells need enzymes?

What pathways help with this function?

A

To create some energy and protect against oxidative damage.

Glycolysis

  • provides energy

Pentose Phosphate shunt

  • protects from oxidative damage
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12
Q

What is G6PD?

What is it’s function?

A

Glucose-6-Phospahte Dehydrogenase

Protects red cell proteins (haemoglobin) from oxidative damage

  • Produces NADPH - vital for reduction of glutathione
  • Reduced glutathione scavenges and detoxifies reactive oxygen species.
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13
Q

Outline G6PD Deficiency.

A
  • Commonest disease causing enzymopathy in the world. - X linked disease
    • As the G6PD cannot carry out it’s function the RBCs are at risk of oxidative damage.
  • It does however confer protection against malaria
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14
Q

How does G6PD Deficiency present?

A
  • Neonatal jaundice
    • Drug, broad bean or infection precipitated jaundice and anaemia.
      • Intravascular haemolysis
      • Haemoglobinuria
    • Splenomegaly - spleen working overtime
    • Pigment gallstones
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15
Q

What is the management of G6PD Deficiency?

A

Avoidance of triggers , notably:

  • Drugs
    • Antimalarial
    • Aspirins
  • Broad beans
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16
Q

Generally outline the strucutre of haemoglobin

A
  • Haem part - contains iron (Fe)
  • 4 globin chains
    • 2 alpha chains
    • 2 beta chains
17
Q

What is the function of haemoglobin?

Which enzyme aids in this function and how?

A

The function of haemoglobin is to carry oxygen.

2,3 - DPG is the enzyme which helps in this function, by more readily releasing oxygen in times of hypoxia.

(Bohr effect)

*Bohr effect - The Bohr Effect refers to the observation that increases in the carbon dioxide partial pressure of blood or decreases in blood pH result in a lower affinity of hemoglobin for oxygen.*

18
Q

Generally outline the genetics behind the chains in haeomglobin.

A

Alpha Chains

  • There are 2 alpha chains.
    • Which are coded for genetically by 4 alpha genes.

Beta Chains

  • There are 2 beta chains
    • Coded for by 2 beta genes

The normal adult will have Hb A (aabb) - 97%

there are other Hb groups, such as foetal Hb, but these are seen in much more limited numbers.

19
Q

What are haemoglobinopathies?

A
  • Inherited abnormalities of haemoglobin synthesis.

These are variable.

Can be in terms of reduced or absent globin chain production

  • Thalassaemia (alpha a, Beta B, delta d, gamma y)

Or can be in terms of mutations leading to structurally abnormal globin cells.

  • Such as in Sickle cell anaemia
20
Q

Where is sickle cell anaemia prevalence?

A

Most prevalent in Africa, with pockets in the med, middle east and india.

21
Q

Where is thalassaemia morst prevalent?

A
  • Med
  • Middle East
  • Asia
  • Asian islands
22
Q

What is the inheritance pattern of sickle cell anaemia?

A

Autosomal Recessive

23
Q

Outline the genetic impact in Sickle Disease.

A
  • Sickle haemoglobin (HbS) composed of haem molecule and:
    • 2 normal alpha chains
    • 2 Beta (sickle) chains
24
Q

What happens to the abnormal RBCs in Sickle Cell Anaemia?

A
  • Normal RBC can cope with being in areas of hypoxia.
  • However, the abnormal chains in Sickle Cell can’t cope with it - and become an abnormal shape when exposed to hypoxia.
25
Q

What is the major impact of HbS (sickle) Polymerisation?

A

The major implication of Sickle Cell Disease (SCD) are

  • Acute chest syndrome
  • Stroke
  • Pain episodes

These are attributed to vaso-occlusive tissue damage.

This is due to th eincreased haemolysis of these cells resulting in various changes in the blood and blood vessel (such as endothelial activation etc.) which can result in vaso-occlusion.

26
Q

What are the clinical presentations of Sickle Cell Disease?

A
  • Painful vaso-occlusive crisis
  • Chest Crisis
  • Stroke
  • Increased infection risk
  • Chronic haemolytic anaemia
    • Gallstones
  • Aplastic crisis
  • Sequestration crises
27
Q

What is aplastic crisis?

A

Complication of Sickle Cell Anaemia

  • if infected by erythrovirus, infected red cells.
  • Haematopoesis can stop, very low haem, can occur in children.
28
Q

What is sequestration crisis?

A

In children, before it infarcts the spleen, flow in, not flow out, causing enlargement of spleen and liver.

  • Spleen – seen often in children.
  • Liver
29
Q

What is painful crisis?

A

Complication of Sickle Cell Anaemia

  • Severe pain - often requires opiates
  • Hydration
  • Oxygen
  • Consider antibiotics
  • No routine role for transfusion.
30
Q

What is Chest crisis in Sickle Cell?

A

Sickling in the lungs

  • Chest pain
  • Fever
  • Worsening hypoxia
  • Infiltrates on CXR

Management

  • Resp Support
  • Antibiotics
  • IV Fliuds
  • Analgesia
  • Transfusion
    • very important
    • exchange transfusion - take away sickle cells, replace with normal.
31
Q

What is the management of Sickle Cell Disease?

A

Life Long Prophylaxis

  • Vaccination
  • Penicillin prophylaxis
  • Folic Acid

Acute Events

  • Hydration
  • Oxygenation
  • Prompt infection treatment
  • Analgesia
    • Opiates
    • NSAIDs

Blood Transfusion

  • Episodic and chronic
  • Alloimmunisation
  • Iron overload

Disease-Modifying Drugs

  • Hydroxycarbamide
    • Increased foetal haemoglobin

Bone Marrow Transplant

32
Q

What are Thalassaemias?

A

Reduced or absent globin chain production.

Mutations or deletions in the genes that code for haemoglobin.

  • In alpha genes
    • Alpha thalassaemia
  • In beta genes
    • Beta thalassaemia
33
Q

What are the various different types of thalassaemias and their respective severity?

A

Homozygous Alpha Zero Thalassaemia

  • no alpha chains
  • Incompatible with life

Beta thalassaemia major (Homozygous beta thalassaemia)

  • No beta chains
  • Transfusion dependent anaemia

“Intermedia”

  • Range of genotypes
  • Non-transfusion dependent

Thalassaemia minor

  • “trait”/carrier state
  • Hypochromic microcytic red cell indices (small red cells very mild anaemia.
34
Q

What is the presentation of Beta thalassaemia Major?

A
  • Present at 3-6 months
  • Expansion of ineffective bone marrow
  • Bony deformities
  • Splenomegaly
  • Growth Retardation

Life expectancy untreated or with regular transfusions <10 years.

35
Q

What is the treatment of Beta Thalassaemia Major?

A
  • Chronic Transfusion support - 4-6 weekly
    • Normal growth and development
      • Transfusions can lead to iron overloading.
      • If untreated can result in premature death due to iron overloading.
      • Treated using iron chelation therapy
  • Bone marrow transplantation can be curative
36
Q

Basically outline sideroblastic anaemia.

A

•Defects in mitochondrial steps of haem synthesis result in sideroblastic anaemia

Haematology (16 decks)

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