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Haematology Y2 > Sickle Cell Disease > Flashcards

Sickle Cell Disease Flashcards

1
Q

What mutation causes sick cell anaemia SCA

A
  • Missense mutation at codon 6 of the gene for  globin chain
  • Glutamic acid is replaced by valine
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2
Q

What does mutation of SCA cause Hb to become and what does this form

A
  • Deoxyhaemoglobin S is insoluble

- HbS polymerises to form fibres TACTOIDS

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3
Q

Polarity / solubility of valine?

A

Non polar, insoluble

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4
Q

Polarity / solubility of glutamic acid

A

Polar, soluble

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5
Q

3 stages in sickling of RBC?

A
  1. DISTORTION
  2. DEHYDRATION
  3. INCREASED ADHERENCE TO VASCULAR ENDOTHELIUM
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6
Q

Pathogenesis of SCD? (3)

A
  • Shortened red cell lifespan (as little as 5-7 days)
  • Anaemia partly due to a reduced erythropoietic drive as HbS is a low affinity Hb
  • Blockage to microvascular circulation (vaso-occlusion):
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7
Q

What does haemolysis of SCs lead to (3)

A

Anaemia
Gallstones
Aplastic Crisis caused by Parvovirus B19

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8
Q

What does blockage to the microvascular circulation by SCs cause (3)

A

Tissue damage and necrosis (infarction)
Pain
Dysfunction

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9
Q

CONSEQUENCES OF TISSUE INFARCTION in the spleen

A

Hyposplenism

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10
Q

CONSEQUENCES OF TISSUE INFARCTION in the bones/joints

A

Dactylitis, avascular necrosis, osteomyelitis (often due to salmonella

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11
Q

CONSEQUENCES OF TISSUE INFARCTION in the skin

A

Chronic/recurrent leg ulcers

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12
Q

Which haemoglobin polymerises to form fibre like structures that disports the shape of the RBC

A

HbS

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13
Q

Cell-free haemoglobin limits XX bioavailability, disturbing Y

A

nitric oxide

vasoregulation

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14
Q

Pathogenesis of SCD in the lungs

A

acute chest syndrome
Chronic damage
Pulmonary hypertension

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15
Q

Pathogenesis of SCD in the urinary tract

A

Haematuria (papillary necrosis)
Impaired concentration of urine (hyposthenuria)
Renal failure
Priapism

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16
Q

What is hyposthenuria

A

Impaired concentration of urine

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17
Q

What is Impaired concentration of urine known as

A

hyposthenuria

18
Q

Pathogenesis of SCD in the brain

A

Stroke

Cognitive impairment

19
Q

Pathogenesis of SCD in the eyes

A

Proliferative retinopathy

20
Q

What does presentation of SCD symptoms coincide with

A
  • Onset coincides with switch from foetal to adult haemoglobin synthesis
21
Q

Early manifestation of SCD? (3)

A

Dactylitis – middle finger is shorter
Splenic sequestration – acute enlargement of the spleen
Infection S. pneumoniae

22
Q

What does an SCD emergencies originate from?

A
  • SEPTIC SHOCK (BP<90/60)
23
Q

Most common cause of death in adults with SCD is….

A

ACUTE CHEST SYNDROME

24
Q

Where does avascular necrosis occur in SCD commonly

A

THE FEMORAL HEAD

25
Q

Stroke in SCD involves ?major/minor? vessels

A

Major

26
Q

What are gallstones a consequence of in SCD

A

Haemolysis

27
Q

LABORATORY FEATURES OF SCD (blood film (4), Hb level)

A
  • Hb low (anaemia) (typically 60-80g/L)
  • Reticulocytes high to try compensate for the low Hb (except in aplastic crisis)
     Blood film Sickled cells, boat cells, holly leaf cells, Howell Jolly bodies
28
Q

DIAGNOSIS OF SCD 2 ways?

A

SOLUBILITY TEST and

ELECTROPHORESIS or HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC

29
Q

Problem with solubility test for diagnosis of SCD?

A

Doesn’t differentiate homozygous from heterozygous SCD

30
Q

General methods of management of SCD? (6)

A
  • Folic acid supplements Adequate folate for blood cell production
  • Penicillin prophylaxis  Against pneumococcal infection
  • Vaccinations
  • Monitor spleen size
  • Blood transfusion for acute anaemic events, chest syndrome and stroke
  • Pregnancy care
31
Q

PAIN CRISIS management of SCD? (5+2)

A
  • Pain relief (opioids)
  • Hydration
  • Keep warm
  • Oxygen if hypoxic
  • Exclude infection:
     Blood and urine cultures
     Chest X-Ray
32
Q

What is used in pain management of SCD? And what’s given as an adjuvent?

A 
Opioids - diamorphine
Adjuvants:
-	Paracetamol
-	NSAIDs
-	Pregabalin/gabapentin
33
Q

Who is HAEMOPOIETIC STEM CELL TRANSPLANTATION used on

A
  • Usually used on <16yr old with severe disease
34
Q

Cure for SCD?

A

Haemoietic stem cell transplant

35
Q

What can be used to treat SCD?

A

INDUCTION TO HbF (drugs that make you switch to making HbF)
and
EXCHANGE TRANSFUSION

36
Q

Drugs that induce change to HbF?

A
  • Hydroxyurea

- Butyrate

37
Q

What do these drugs do?

  • Hydroxyurea
  • Butyrate
A

induce change to HbF

38
Q

What 3 disease modifying therapies for SCD are there

A
  1. Transfusion
  2. Hydroxycarbamide (hydroxyurea)
  3. Haemopoietic stem cell transplantation
39
Q

How does hydroxyurea work

A
  • Increases foetal haemoglobin production (HbF)
  • Decreases ‘stickiness’ of sickle RBCs
  • Reduces white cell production by bone marrow
  • Improves hydration of RBCs
  • Generates NO which improves blood flow
40
Q

Explain why infants with SCD don’t usually develop symptoms until >3months

A
  • HbF inhibits polymerisation of HbS
41
Q

Indications for bone marrow transplantation in SCD? (3)

A
  • CNS disease
  • Recurrent severe vaso-occlusive crises IF HYDROYUREA FAILS
  • Recurrent acute coronary syndromes (ACS) IF HYDROYUREA FAILS
42
Q

Limitations of HSCT in SCD?

A

Donor availability
1-2% of children with SCD qualify
6 months of treatment
Infertility and other long term problems

Haematology Y2 (11 decks)

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