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HMS301 Blood & Neoplasia > Sickle Cell Disease > Flashcards

Sickle Cell Disease Flashcards

1
Q

Sickle Cell Disease

A

genetic disorder that results from the presence of a mutated form of Hb = HbS (sickle Hb)

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2
Q

Pathology

A
  • Single base-pair point mutation (GAG to GTG) in the beta-globin gene = glutamic acid or glutamate (hydrophilic) is replaced by valine (hydrophobic) at position 6 of the beta globin molecule = resulting in the formation of HbS.
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3
Q

Unique feature of sickle hemoglobin (HbS)

A

Polymerizes (combines) on deoxygenation

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4
Q

HbS polymerization causes…

A
  • Crises = erythrocyte sickling, leading to vaso-occlusion & episodes of ischemia.
  • vaso-occlusion = blood vessels become blocked = sickled cells are stiff & sticky = don’t move freely through the blood vessels.
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5
Q

Most common form of sickle cell disease (SCD)

A
  • homozygous HbS disease = autosomal recessive disorder.
  • found in North America
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6
Q

SCD causes significant morbidity & mortality particularly in?

A
  • African people
  • People with Mediterranean & Middle Eastern ancestry.
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7
Q

True or False
- Morbidity, frequency of crisis, degree of anemia, & the organ systems involved vary considerably from individual to individual.

A

True

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8
Q

For the first _________ of life, infants are protected largely by elevated levels of fetal hemoglobin (HbF).

A

6 months

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9
Q

Most common clinical manifestation of SCD

A

Vaso-occlusive crisis

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10
Q

Most distinguishing clinical feature of SCD

A

Pain crises

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11
Q

Signs & Symptoms of SCD

A
  • Bone pain
  • Anemia
  • Aplastic crisis
  • Splenic sequestration
  • Infection
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12
Q

Bone pain

A
  • Primarily due to bone marrow infarction.
  • Often seen in long bones of extremities.
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13
Q

Anemia

A
  • universally present
  • very well tolerated
  • Patients with Hb level of 6-7 g/dL = are able to participate in daily life activities BUT have very limited tolerance for exercise & exertion.
  • can be complicated with megaloblastic changes secondary to folate deficiency (results from ↑ RBC turnover & folate utilization).
  • Periodic bouts of Hyperhaemolysis may occur.
  • Few manifestations of anemia in children = because they readily adjust by ↑HR & SV BUT they have ↓ stamina.
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14
Q

Aplastic crisis

A
  • serious complication = temporary shutdown of RBC production in bone marrow.
  • caused by an infection with Parvovirus B-19 (B19V) = infects RBC progenitors in bone marrow resulting in impaired cell division for a few days.
  • self-limited condition = with bone marrow recovery occurring in 7-10 days, followed by brisk reticulocytosis (↑ immature RBCs).
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15
Q

Fifth disease - Parvovirus B-19 (B19V)

A
  • benign childhood disorder associated with fever, malaise & a mild rash.
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16
Q

RBC lifespan in healthy people vs SCD patients

A
  • Healthy people = experience a slight drop in hematocrit, since the half-life of normal erythrocytes in the circulation is 40-60 days.
  • SCD patients = RBC lifespan is greatly shortened (usually 10-20 days) & a very rapid drop in Hb occurs.
17
Q

Splenic sequestration

A
  • excessive amounts of blood trapped in the spleen, causing a dangerous drop in the circulating blood volume.
  • occurs with highest frequency during the first 5 years of life in SCD children.
  • Characterized by the onset of life-threatening anemia with rapid enlargement of the spleen & high reticulocyte count.
  • Medical emergency that demands prompt & appropriate treatment = early recognition, careful monitoring & aggressive transfusion support.
18
Q

Infection

A
  • encapsulated respiratory bacteria = Streptococcus pneumoniae.
  • adult infections = gram negative = Salmonella.
19
Q

Signs & Symptoms of SCD

A
  • growth retardation
  • delayed sexual maturation
  • underweight
20
Q

Affected pubertal males

A
  • shorter & have significantly slower height growth than their unaffected counterparts, with a decline in height over time.
21
Q

Hand-foot syndrome

A
  • dactylitis = presents as bilateral painful, swollen hands &/or feet in children.
  • develops suddenly & lasts 1-2 weeks.
  • occurs between 6 months & 3 years = not seen after age 5 because hematopoiesis in the small bones of the hands & feet ceases at this age.
  • Cortical thinning & destruction of the metacarpal & metatarsal bones appear on radiographs 3-5 weeks after the swelling begins.
  • major differential diagnosis = osteomyelitis
22
Q

Acute chest syndrome in young children & adults

A
  • young children = chest pain, fever, cough, tachypnea, leukocytosis & pulmonary infiltrates in the upper lobes.
  • adults = usually afebrile & dyspneic with severe chest pain & multilobe & lower lobe disease.
23
Q

Acute chest syndrome

A
  • medical emergency where untreated immediately = patients are at risk of developing acute respiratory distress syndrome.
  • probably begins with infarction of the ribs, leading to chest splinting & atelectasis.
24
Q

In children, acute chest syndrome is usually due to…

A
  • infection
  • other etiologies = pulmonary infarction & fat embolism resulting from bone marrow infarction.
25
Q

Central nervous system involvement = Stroke

A
  • Stroke = affects 30% of children & 11% of patients by 20 years.
  • in children = ischemia
  • in adults = hemorrhagic
  • hemiparesis + convulsions
26
Q

Causes of stroke in SCD

A
  • rapid & excessive blood transfusion to a Hb level of >12 g/dL increases blood viscosity & can lead to stroke.
  • Hemorrhagic stroke = often caused by rupture of aneurysms.
27
Q

Cardiac involvement

A
  • hemosiderin deposition in the myocardium.
  • systolic murmur
28
Q

Cholelithiasis / Gallstones

A
  • common in children
  • chronic hemolysis with hyperbilirubinemia is associated with the formation of bile stones.
29
Q

When to consider cholelithiasis in a child?

A
  • child who presents with RUQ pain, especially if associated with fatty food.
30
Q

When to consider common bile duct blockage?

A
  • when a child presents with RUQ pain & dramatically elevated conjugated hyperbilirubinemia.
31
Q
A

HMS301 Blood & Neoplasia (8 decks)

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