Hemoglobin genetics, sickle cell crises and complications, alpha and beta thalassemia genotypes, screening, and disease-modifying therapies.
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- What point mutation causes sickle cell disease?
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Glutamic acid is replaced by valine at position 6 of the beta-globin chain.- What is the inheritance pattern of sickle cell disease?
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Autosomal recessive.- What genotype defines sickle cell trait?
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Heterozygous HbAS, one normal beta-globin allele and one sickle allele.- What condition causes hemoglobin S molecules to polymerize and deform red cells?
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Deoxygenation of hemoglobin S.- What is dactylitis and when does it typically first appear in sickle cell disease?
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Painful swelling of the hands and feet (hand-foot syndrome), often the first manifestation in infancy.- How is acute chest syndrome defined in sickle cell disease?
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A new pulmonary infiltrate on chest imaging plus fever or respiratory symptoms.- What happens during a splenic sequestration crisis?
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Sickled cells trap blood in the spleen, causing a rapid drop in hemoglobin and risk of hypovolemic shock.- Why do most adults with sickle cell disease have functional asplenia?
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Repeated splenic infarction over time destroys splenic function, known as autosplenectomy.- Which type of organism poses the greatest infection risk in functionally asplenic sickle cell patients?
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Encapsulated organisms, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis.- What infection classically causes aplastic crisis in sickle cell disease?
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Parvovirus B19, which infects erythroid precursor cells.- What is priapism, as seen in sickle cell disease?
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A prolonged, painful erection caused by vaso-occlusion impairing penile venous outflow.- What bone complication from vaso-occlusion commonly affects the femoral head in sickle cell disease?
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Avascular necrosis.- What screening test is used to assess stroke risk in children with sickle cell disease?
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Transcranial Doppler ultrasound.- What is the main mechanism of hydroxyurea in treating sickle cell disease?
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It increases production of fetal hemoglobin (HbF), which interferes with HbS polymerization.- What clinical benefit does hydroxyurea provide to sickle cell patients?
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It reduces the frequency of vaso-occlusive pain crises and episodes of acute chest syndrome.
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