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POM HAEM > Haemoglobinopathy > Flashcards

Haemoglobinopathy Flashcards

1
Q

What causes HbS to form?

A

A missense mutation in the beta globin gene which results in a valine substitution for glutamic acid

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2
Q

What happens to HbS at low oxygen levels?

A

The de-oxy Hb polymerises into long intracellular fibres = tactoids which conforms the RBS into a highly unflexible sickle shape, which are more sticky and therefore cannot flow through the blood vessels

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3
Q

What is the solubility like of HbS?

A

it is highly insoluble

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4
Q

Which condition does the distribution of the Sickle Cell gene match?

A

Plasmodium falciparum malaria

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5
Q

Where is HbS particularly prevalent?

A

In tropical Africa and some parts of the Miditerranean, Middle East and India

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6
Q

What is the phenotype of person carrying two copies of the Beta sickle gene?

A

Sickle Cell Anaemia

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7
Q

What is the lifespan of a sickled red blood cell like compared with a normal one?

A

10-20 days, compared with the 120 normal days

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8
Q

Why might a patient with sickle cell anaemia have a high reticulocyte count?

A

The bone marrow compensates for the destruction of sickle cells by producing more red blood cells, hence an increase in immature RBCs

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9
Q

Which type of blood cells might specifically be seen on a blood film?

A

Reticulocytes, target cells (Howell-Jolly Bodies) and Sickle Cells

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10
Q

What are Howell-Jolly Bodies?

A

Cells with DNA still present in the center of the cell - arises when patients have reduced splenic function

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11
Q

Why does sickle cell disease lead to splenic complications?

A

The microvasculature of the spleen is a prime place for sickling vaso-occlusion to occur - repeated occlusions leads to destruction and engoregement of the spleen with blood (spleen sequestration)

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12
Q

Why is haemolysis increased in SCD?

A

The RBCs have a shorter life span (20 days), and therefore are destroyed more quickly - when the spleen cannot cope with this high load, it can lead to pooling in the spleen

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13
Q

Why might you find elevated gall stones in patients with SCD?

A

More bilirubin is produced as there is more haemolysis of the RBCs, which as a result leads to more gall stones forming

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14
Q

Why might jaundice occur in patients with SCD?

A

More haemolysis of RBC = more bilirubin forming, leaving yellow tint to the skin and sclera of the eye

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15
Q

What is a common early manifestation of SCD?

A

Dactylitis which is inflammation of the digits

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16
Q

What is hypopslenism?

A

When the spleen doesnt work any more due to repeated vaso-occlusion

17
Q

What can hyposplenism lead to in terms of infection?

A

Increased succeptibility to encapsulated bacterial infections

18
Q

What are sickle cell crises?

A

Vaso-occlusive crises which are a hallmark of sickle cell diease

They are acute episodes of pain, usually felt in the lower back, pelvis and legs

19
Q

Why are SCD patients given hydroxyurea?

A

Hydroxyurea stimulates the production of HbF which has a high affinity for Oxygen, and therefore reduce the recurrent episodes of vaso-occlusive crises which SCD patients may face

20
Q

In patients heterozygous for the beta sickle gene, what is seen on gel electrophoresis?

A

Both HbA and HbS are seen

21
Q

What is acute chest syndrome in SCD?

A

Vaso-occlusion of the pulmonary vasculature, which should be treated as a medical emergency

22
Q

How is acute chest syndrome diagnosed?

A

New pulmonary infiltrate on chest X-ray
with Fever
Cough
Chest pain
Tachypnoea (rapid breathing)

23
Q

What other conditions can SCD cause?

A

Stroke, Hyposplenism, jaundice, Acute Chest Syndrome, Avascular necrosis of femoral head, Osteomyelitis

24
Q

How does the sickle solubility test work in diagnosing SCD

A

In the presence of a reducing agent oxyHb converted to deoxy Hb
Solubility decreases
Solution becomes turbid

25
Q

What is the problem with the sickle solubility test in the diagnosis of SCD?

A

Does not differentiate AS from SS

26
Q

What does the definitive diagnosis of SCD require?

A

Definitive diagnosis requires Electrophoresis or High Performance Liquid Chromatography (HPLC) to separate proteins according to charge

POM HAEM (10 decks)

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