Sickle Cell Disease Flashcards

1
Q

Recall the prevalence of SCA in the UK?

A

Most prevalent monogenic disorder in UK

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2
Q

What is genotype that produces full SCA?

A

HbS HbS

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3
Q

Recall two compound heterozygous states of sickle cell disease

A
  1. SC (C is another structural variant of HbC)

2. S-beta-thalassaemia = HbS and beta thalassaemia

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4
Q

Recall the variance of symptoms in sickle cell anaemia

A

Even those with same genotype can be clinically heterogenous

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5
Q

What does the term “sickle cell disease” refer to?

A

Any disease state that results from sickling

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6
Q

Recall the 2 pathogenesis pathways that lead to anaemia in sickle cell disease

A
  1. Shortened red-cell lifespan –> haemolysis

2. Reduced erythropoietic drive due to HbS having a low O2 affinity

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7
Q

What is the difference between HbA and HbS?

A

Glutamic acid replaced by a valine at position 6

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8
Q

Other than anaemia, what 2 pathologies are often seen in sickle cell disease as a direct result of shortened red cell lifespan?

A

Gall stones

Aplastic crisis

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9
Q

What is an aplastic crisis and what is its most likely cause?

A

Temporary cessation of erythropoiesis

Parvovirus B19

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10
Q

What are the 3 categories of pathology seen in sickle cell disease?

A

Haemolysis
Blockage to microvascular circulation
Limited NO availability

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11
Q

What are the 3 main effects of microvascular circulation being blocked in sickle cell disease, and what are the subsequent effects of these?

A

Pain, dysfuction adn tissue necrosis

Necrosis –> bone disorders, skin ulceration and hyposplenism (due to repeated vaso-occlusive damage)

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12
Q

What is the main effect of NO availability being limited in sickle cell disease? What causes availability to be low?

A

Pulmonary hypertension

Low due to NO being free in plasma following haemolysis

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13
Q

When do symptoms of sickle cell disease first present and why?

A

Around 6 months when transition is made between HbF and HbA

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14
Q

What are the 3 primary early manifestations of sickle cell disease?

A

Dactylitis
Splenic sequestration
Infection

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15
Q

What is splenic sequestration?

A

Sudden acute pooling of blood in spleen

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16
Q

What sort of infection is commonly seen in early sickle cell disease and why?

A

Pneumococcal - this is an encapsulated bacteria and so more likely to occue in SCD as there is hyposplenism

17
Q

Recall 3 later-stage manifestations of sickle cell disease (pre-crisis)

A

Stroke
Gall stones
The acute chest syndrome

18
Q

Why is the risk of gallstones increased in sickle cell disease?

A

Co-inheritance of Gilbert syndrome

19
Q

What is the acute chest syndrome?

A

Vaso-occlusive crisis of pulmonary vasculature

20
Q

Recall 4 symptoms of sickle cell emergencies

A

Septic shock
Cerebral haemorrhage
Hypoxia
Priapism

21
Q

Recall the 2 main consequences sickling of red cells

A

Dehydration of cells

Increased adherence to vascular endothelium

22
Q

What is the main feature of sickle cell disease shown by an FBC

A

High reticulocytes

23
Q

What 4 structures can be identified on a blood film that is positive for sickle cell disease

A

Sickled cells (obviously)
Boat cells
Target cells
Howell-Jolly bodies

24
Q

What is the first test done in suspected sickle cell disease and how does it work?

A

Solubility test: in the presence of a reducing agent ocyHb –> Hb causing solubility to decrease and solution to become turgid

25
What method is used to definitively diagnose sickle cell disease?
HPLC
26
Recall 2 preventative measures used in sickle cell disease?
Prophylactic penicillin for encapsulated bacteria infection risk Train parents to examine abdomen for splenomegaly
27
What supplement is given in sickle cell disease, and why?
Folic acid | Supplies folate for haematopoiesis
28
Name and explain the mechanism of action of a drug used to treat sickle cell disease
Hydroxyurea: introduces HbF into blood to prevent sickling