ABSTRACT
Studies of the natural history of sickle cell disease (SCD) have shown a median life expectancy for adults with SCD of 42-53 years for men and 48-59 years for women (1,2). Patients with hemoglobin (Hgb) SS disease have a higher incidence of death than other sickle disorders, such as Hgb SC or Hgb Sb0 thalassemia (3). The proportion of patients with Hgb SS surviving to age 20 years was 85%, when reported by Leikin in 1989 (3). More contemporary survival and natural history studies are lacking. Lower steady-state Hgb, higher reticulocyte counts, white blood cell counts O15,000/mm3, and Hgb F !15% are predictive of a higher rate of death (3). Similar analyses for patients at two years of age have shown that leukocytosis, early dactylitis, and severe anemia (Hgb !7 gm/dl) were predictive for severe SCD (4). Up to 11% of patients suffer clinical strokes, and an additional 17-22% will suffer a subclinical “silent” infarction evident on brain magnetic resonance imaging (MRI) (5). Treatment with chronic red blood cell transfusions to prevent additional strokes or acute chest syndrome can lead to red blood cell alloantibodies and autoantibodies (6) and iron overload (7).
