A rare, genetic hemoglobinopathy characterized by all the characteristics of sickle cell anemia (SCA). Clinical course is similar to SCA, including acute episodes of pain, splenic infarction and splenic sequestration crisis, vaso-occlusive crisis, acute chest syndrome, ischemic brain injury, osteomyelitis and avascular bone necrosis. The genotype is characterized by an HbS allele in combination with the HbD variant, beta121Glu>Gln.