Erythrocyte cellular and membrane deformability in hereditary spherocytosis.

In order to determine whether the relative rigidity of the hereditary spherocytosis (HS) red cell is due to membrane rididity or merely to an altered surface/volume ratio, we investigated the deformability of resealed red cell membranes from patients with HS. Whereas the osmotic fragility of intact red cells of HS patients showed the expected increase, the osmotic fragility of resealed HS membranes was normal, thus indicating that their surface/volume ratio was normal. Measurements with an ektacytometer showed that deformability of intact HS cells was markedly diminished, whereas deformability of resealed HS membranes was normal. These findings indicate that the HS red cell membrane is not intrinsically abnormally rigid, as has been suggested, but that the lack of deformability of the erythrocyte is primarily a function of the altered surface/volume ratio.