[Study of erythrocyte deformability using visco-diffractometry (ektacytometry) in hereditary hemolytic anemias].

Deformability is a basic characteristic of red blood cells; its regulating factors are presently well known (surface volume ratio, internal viscosity, viscoelastic properties of the membrane). The contribution of each of these factors in the pathogeny of hemolytic anemias has not been fully established. We report 64 hereditary hemolytic anemias in which we studied the deformability, using a visco-diffractometric method (ektacytometer) on whole blood and various subpopulations separated by density. Comparison of the response of the cells submitted to isotonic and hypotonic media allows the determination of the respective contribution of viscosity and surface volume ratio. Deformability is always decreased in red blood cell membrane diseases and in homozygous or double heterozygous hemoglobinopathies; on the other hand, deformability is normal in all the enzymopathies studied. This decrease could be due either to one regulation factor (increase of internal viscosity easily demonstrated by this method in hereditary xerocytosis and hemoglobin CC) or to several parameters: increase of internal viscosity and decrease of surface volume ratio in hereditary spherocytosis.