Rheologic properties of erythrocytes in Duchenne muscular dystrophy

The transformation of erythrocytes into echinocytes by suspension in isotonic phosphate buffer was increased in patients with Duchenne muscular dystrophy (DMD) as compared to healthy controls. The transformation was enhanced when glass slides instead of polystyrole slides were used for observation. Viscosity of erythrocyte suspensions with a hematocrit of 80% was the same in patients and controls. The mean flow rate of erythrocyte suspensions in autologous plasma was only slightly reduced in the patient group, but decreased markedly after suspension of the cells in phosphate buffer, without as well as after preincubation with 10 mM Na salicylate. The decreased flow rate in patients is probably due to the increased number of echinocytes and not to an increased membrane rigidity, because the membrane flexibility of isolated ghosts, measured in a viscosimeter, was normal at all shear rates. Echinocyte formation in patients with DMD is strongly dependent on the techniques applied and difficult to evaluate quantitatively by phase contrast microscopy. Filtration of erythrocyte suspensions seems to be a more reliable, quantitative test for increased erythrocyte vulnerability.