Sickle-cell trait and sickle-cell anaemia

Abstract

Arguments and evidence are presented to substantiate the belief that sickle-cell trait is a heterozygous (Ss) state and that sickle-cell anaemia is a homozygous (SS) state and that each is inherited according to simple Mendelian law. Sickle-cell anaemia has recently been shown to be much more common among African negroes than has heretofore been reported, but since SS individuals do not have a very long life expectancy, the high rate of infant mortality has carried off the majority of such homozygous individuals and figures based on surveys among adults have been misleading to most investigators. Case histories are presented that contradict the belief that the appearance of sickle-cell anaemias is always indicative of negro ancestry. It is also shown that anaemias of other origin cannot be grafted on to sickle-cell trait, therefore sickle-cell anaemia as a hereditary condition must come from the crossing of SS x SS, SS x Ss, or Ss x Ss.