Sickle cell disease

Sickle cell disease is a group of inherited disorders caused by abnormal hemoglobin that can make red blood cells rigid, sickle-shaped, and prone to breaking or blocking blood vessels.

Hemoglobin S: A hemoglobin variant that can polymerize when deoxygenated and deform red blood cells. Its deoxygenation-triggered polymerization initiates sickling in the disease.
Hemoglobin: The oxygen-carrying protein in red blood cells, built from globin chains and heme groups. Sickle cell disease begins with a change in one of hemoglobin’s globin chains.
Newborn screening: Testing shortly after birth to identify conditions before symptoms appear. Early detection enables preventive care before sickle cell complications emerge.
Stroke: Brain injury caused by interrupted blood flow or bleeding within the brain. Sickle cell disease can obstruct cerebral vessels and cause childhood stroke.
Hemoglobin polymerization: The assembly of hemoglobin molecules into long fibers under particular conditions. Low oxygen lets hemoglobin S form fibers that distort red cells.
HBB: The gene on chromosome 11 that encodes the beta-globin subunit of hemoglobin. The disease-causing variants alter the beta-globin encoded by this gene.
Transcranial Doppler ultrasonography: An ultrasound test that measures blood-flow velocity in major brain arteries. It identifies children at increased risk of stroke and guides preventive transfusions.
Avascular necrosis: Bone tissue death caused by inadequate blood supply. Repeated vessel blockage can damage bone, especially the hip and shoulder.
Vaso-occlusive crisis: An episode in which obstructed small blood vessels cause acute pain and tissue injury. Rigid, adhesive cells obstruct vessels and produce these hallmark episodes.
Autosomal recessive inheritance: An inheritance pattern in which a condition usually develops after inheriting two disease-causing gene copies. Most forms require disease-associated globin variants from both parents.

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