Two patients with hereditary spherocytosis had increased autohemolysis not corrected by supplementary glucose, while an affected son of the second patient had a typical autohemolytic response with glucose. Almost one half of the circulating red cells in both patients had markedly increased osmotic fragility. When these were eliminated in vitro, by selective osmotic hemolysis, or in vivo by splenectomy, the autohemolysis response was corrected by glucose. The loss of this large population of extremely fragile cells after splenectomy suggested they were the product of conditioning by the spleen.
In addition to having decreased osmotic resistance, an autohemolysis not corrected by glucose, and a short in vivo survival, these conditioned cells were smaller and had a considerable decrease in cell lipid. After splenectomy, with the loss of the most fragile cell population, cell size and lipid content increased. However in spite of no decrease in cell lipid after splenectomy, osmotic fragility remained abnormal. Increased osmotic fragility may be one of the earliest manifestations of a membrane abnormality in hereditary spherocytosis.