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Year 2 > Sickle Cell Anaemia > Flashcards

Sickle Cell Anaemia Flashcards

1
Q

Where is Sickle Cell Anaemia common

A

Africans - India, Middle East + southern Europe

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2
Q

Inheritance pattern of SCA

A

Autosomal Recessive

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3
Q

How is it caused

A

Production of abnormal beta-globing chains

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4
Q

Chances of getting the disease

A

1 in 4

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5
Q

Chance of being a carrier

A

50%

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6
Q

Chance of being disease free

A

1 in 4

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7
Q

Risk factors of SCA

A

African

Family History

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8
Q

Genetic mutations that cause SCA

A

Single-base mutation of Adenine to Thymine which substitutes Valine for Glutamic Acid at 6th codon of beta-globing chain

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9
Q

What is the heterozygous state called

A

Sickle cell trait

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10
Q

Why does SCA not manifest until 6th month of age

A

Because currently baby is running on HbF which is normal - starts becoming a problem when HbF starts to decrease

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11
Q

Properties of HbS

A

Insoluble and polymerises when deoxygenated

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12
Q

What happens to flexibility of cells

A

Decreases + become rigid

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13
Q

Initially, is sickle cell process reversible

A

Yes

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14
Q

How does this become an irreversible process

A

Cells eventually lose membrane flexibility with repeated sickling (become dehydrated and dense - won’t return to normal when oxygenated)

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15
Q

How does sickling effect lifespan of RBS

A

reduced due to haemolysis

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16
Q

How does sickling effect circulation

A

Impaired passage through microcirculation -> infarctions

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17
Q

What precipitates sickling

A 
Infection
Cold
Dehydration
Acidosis
Hypoxia
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18
Q

Affinity of HbS to oxygen

A

Low - easily dissociates oxygen to normal RBCs - patients feel well even though anaemic

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19
Q

Clinical presentation of heterozygous sickle cell trait

A

Asymptomatic

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20
Q

When are sickle cell trait people disabled

A

Hypoxia (vasco-occlusive events will occur)

21
Q

What benefit does sickle cell trait have

A

Falciparum Malaria

22
Q

Why is acute pain felt in the hands and feet in SCA

A

Vado-Occlusion of small vessels and avascular necrosis of bone marrow of children

Adults - pain along long bones due to avascular necrosis of bone marrow

CNS infarctions - strokes in children

23
Q

What is acute chest syndrome

A

Pulmonary hypertension and chronic lung disease due to faso-occlusive crisis of pulmonary vasculature

24
Q

What is Acute chest syndrome caused by

A

Infection, fat embolism from necrotic bone marrow or pulmonary infarction due to sequestration of sickle cells

25
Q

What is sequestration of sickle cells

A

Sickle cells gets trapped in pulmonary vasculature

26
Q

Signs of ACS

A

shortness of breath, chest pain and hypoxia

27
Q

What defines pulmonary hypertension

A

Pulmonary artery pressure greater than 25 mmHg by right heart catheterisation

28
Q

How common is pulmonary hypertension in SCA

A

affects 10%

29
Q

What bacteria can cause acute chest syndrome

A

Chlamidyia
Mycoplasma
Strep. pneumoniae

30
Q

How does HbS cause anaemia

A

Splenic sequestration (sickle cells get trapped in spleen) - acute enlargement of spleen that is painful and fall in Hb

Bone marrow aplasia - rapid fall in haemoglobin with no reticulocytes in the peripheral blood because of the failure of erythropoiesis in the marrow

31
Q

How does splenic sequestration effect the spleen

A

Leads to a fibrotic, non-functioning spleen

32
Q

When does bone marrow aplasia follow

A

Follows infection with Erythrovirus B19 which invades proliferating erythroid progenitors

33
Q

Problems of SCA on growth + development

A

Young children start short + become normal height by adulthood

Remain below normal weight

Sexual maturation is delayed

34
Q

Long-term problems on bones

A
  1. Vaso-occlusive crises = avascular necrosis of hips + shoulders, compression of vertebrae and shortening of bones in hands and feet

Osteomyelitis

35
Q

Why would osteomyelitis occur

A

Due to Staph A, Staph. pneumonia and salmonella

36
Q

Long-term cardiac issues

A

Cardiomegaly, arrhythmias, iron overload myocardipathy

MI

37
Q

Long-term near issues

A

TIA, fits and coma

38
Q

How does SCA effect liver

A

Chronic hepatomegaly, liver dysfunction due to trapping of sickle cells

39
Q

How does SCA effect Renal

A

Chronic tubulointerstitial nephritis

40
Q

How does SCA effect Eye

A

Retinopathy, vitreous haemorrhage and retinal detachments

41
Q

How does SCA effect pregnancy

A

Impaired placental blood flow - abortion

42
Q

Blood count

A

Hb range 60-80 g/L

Raised reticulocyte count

43
Q

Blood film

A

Sickled erythrocytes shown

44
Q

Result of sickle solubility test

A

POSITIVE

45
Q

How does Hb electrophoresis confirm diagnosis and when is it done

A

Shows 80-95% HbS and absent HbA

At birth

46
Q

How is it treated

A

Precipitating factors controlled

Folic Acid TO ALL

47
Q

How are acute painful attacks treated

A
  1. IV fluids
  2. Analgesia (NSAIDS, morphine)
  3. Oxygen and antibiotics
48
Q

How is anaemia treated

A
  1. Blood transfusion (risk of iron overload)

2. ORAL HYDROXYCARBAMIDE)

49
Q

Role of Oral Hydroxycarbamide

A

Increases hbF conc.

Year 2 (155 decks)

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