Sickle Cell Flashcards
(65 cards)
What are modifiers of sickle cell disease?
Factors influencing clinical severity and manifestations
Modifiers include haplotypes, co-inheritance with alpha thalassemia, and levels of Hb F.
What causes gradual decrease in haematocrit in sickle cell disease?
Folate deficiency and chronic renal insufficiency
Chronic renal insufficiency affects erythropoietin production.
What are acute exacerbations in sickle cell disease?
Aplastic crisis, splenic sequestration
These can lead to severe complications in patients.
At what age do infants with sickle cell disease show a decline in haematocrit?
12 to 15 months
Infants have lower than normal haematocrit after the neonatal period.
What is the relationship between haematocrit levels and stroke risk in sickle cell disease?
Lower haematocrit increases stroke risk; higher haematocrit increases painful episodes
Patients with lower baseline haematocrit are at greater risk for stroke and renal dysfunction.
What are the two major pathophysiologic mechanisms of clinical features in sickle cell disease?
Haemolytic and vasoocclusive
These mechanisms explain the clinical manifestations observed in patients.
What characterizes a haemolytic crisis in sickle cell disease?
Pronounced haemolysis and laboratory findings of haemolysis
Caused by infections, transfusion reactions, or sepsis.
What is a sequestration crisis?
Massive pooling of red cells in the spleen
Typically seen in children under 5 years and can recur in about half of survivors.
What causes an aplastic crisis in sickle cell disease?
ParvoB19 virus infection
This virus attaches to P-antigen on erythroid progenitor cells, leading to temporary erythropoiesis arrest.
What is a vasoocclusive crisis?
Acute painful crisis common in young adults
Often precipitated by cold, dehydration, or stress.
Which pathogens are commonly associated with infections in sickle cell disease patients in Africa?
Salmonella spp, Klebsiella spp, E. coli, Staphylococcus spp
These organisms are responsible for various infections in this population.
What is the most common organism causing pneumonia in sickle cell disease patients?
Streptococcus pneumoniae
Other common causes include Mycoplasma pneumoniae and Chlamydia pneumoniae.
What is the risk of stroke in patients with sickle cell disease?
Approximately 11% of patients younger than 20 years
Stroke types vary with age; ischaemic stroke is most common in children.
What is the effect of anaemia on cardiac output in sickle cell disease?
Increased cardiac output due to elevated stroke volume
Hyperdynamic circulation may lead to clinical manifestations like murmurs and tachycardia.
What percentage of sickle cell disease patients experience pulmonary hypertension?
6 to 11%
Contributing factors include abnormalities in nitric oxide metabolism and inflammation.
What defines acute chest syndrome in sickle cell disease?
New infiltrate on chest radiograph, chest pain, fever, tachypnoea
It is the leading cause of death among sickle cell anaemic patients.
What is the best predictor of stroke risk in sickle cell disease?
Increased blood flow velocity in intracranial arteries
Velocities greater than 200 cm/s are associated with a higher stroke risk.
What are the four major crises identified in sickle cell disease?
Vasoocclusive, aplastic, haemolytic, sequestration
Each crisis has distinct features and management strategies.
What role do environmental and genetic factors play in the clinical course of sickle cell disease?
They influence the severity and frequency of complications
Some patients may live a normal life while others face frequent hospitalizations.
What is the role of nitric oxide in the vascular endothelium?
Vasodilatory, anti-inflammatory, and antiplatelet properties
Nitric oxide is synthesized from L-arginine by endothelial nitric oxide synthase.
What happens to nitric oxide synthesis during haemolysis in sickle cell disease?
It decreases due to the release of L-arginase
This reduces the available L-arginine for nitric oxide production.
How does sickle cell dehydration occur?
Impaired cation homeostasis and loss of intracellular potassium
This leads to increased red cell haemoglobin concentration and promotes sickling.
What factors influence the polymerization of Hb S?
Oxygenation status, intracellular haemoglobin concentration, presence of non-sickle haemoglobins
Acidosis and elevated 2,3-DPG levels promote polymer formation.
What is the laboratory profile of sickle cell anaemia?
Evidence of haemolysis, increased LDH, indirect bilirubin, high reticulocyte count
Decreased serum haptoglobin is also observed.
