About Sickle Cell Disease
SCD is a lifelong inherited blood disorder caused by a genetic mutation in the beta-chain of hemoglobin, which leads to the formation of abnormal hemoglobin known as sickle hemoglobin (HbS). In its deoxygenated state, HbS has a propensity to polymerize, or bind together, forming long, rigid rods within a red blood cell (RBC). The polymer rods deform RBCs to assume a sickled shape and to become inflexible, which causes hemolytic anemia (the destruction of RBCs) that can lead to multi-organ damage and early death. This sickling process also causes blockage in capillaries and small blood vessels. Beginning in childhood, SCD patients typically suffer unpredictable and recurrent episodes or crises of severe pain due to blocked blood flow to organs, which often lead to psychosocial and physical disabilities.
In its deoxygenated state, HbS has a propensity to polymerize, or bind together into long, rigid rods within an RBC, much like a "sword within a balloon." As a consequence, the normally round and flexible RBC becomes rigid and elongated into a “sickled” shape. Polymerization causes the destruction of RBCs, known as hemolytic anemia. In addition, sickled RBCs, which do not flow properly in the bloodstream, clog small blood vessels and reduce blood flow to the organs. This results in inadequate oxygen delivery, or hypoxia, to all body tissues.
Who SCD Affects:
There are 90,000 to 100,000 SCD patients in the U.S., 60,000 SCD patents in Europe, and millions worldwide. SCD is a congenital disease, and symptoms and organ damage begin within the first years of life. This makes newborn screening (required in all states in the U.S.) and pediatric development of new therapeutics critical. Approximately one in 365 African American children in the U.S. is born with SCD and the global incidence of SCD is estimated to be 250,000 to 300,000 births annually. The disease is concentrated in populations of African, Middle Eastern and South Asian descent.
Among children with SCD, roughly 10–15 percent will suffer an overt stroke. Many more will experience one or more silent strokes, which are associated with brain damage and cognitive impairment.
The Need for New SCD Treatments:
SCD represents a global health problem and new treatment options are desperately needed.
Beginning in early childhood, SCD patients suffer unpredictable and recurrent episodes or crises of severe pain due to hypoxia (inadequate oxygen delivery to body tissues) and hemolytic anemia (the destruction of RBCs). This can lead to multi-organ damage and early death. A recent publication noted that in the United States, SCD results in a decrease of approximately 25 to 30 years in life expectancy.
SCD is also associated with high treatment costs. One study estimated that in the United States, the average annual cost for the care of an adult patient with the most common genotype of SCD exceeds $200,000. This equates to cumulative lifetime costs in excess of $8.0 million over an assumed 50-year lifespan, driven primarily by hospital admissions, physician fees, clinic and emergency department visits, and the costs of diagnostic procedures and outpatient consultations.