Red cell deformability and lipid composition in two forms of acanthocytosis: Enrichment of acanthocytic populations by density gradient centrifugation

Whole cell deformability and lipid determinations were performed on red cells from two patients who had acanthocytes in the peripheral blood (10% and 20% to 30%) and normal serum lipoprotein levels. One patient had typical chorea-acanthocytosis and the other had no clinical abnormalities associated with acanthocytosis. Red cells from the patient with chorea-acanthocytosis showed reduced deformability, as measured by a visco-diffractometric method (ektacytometry), which could be explained by the presence of increased numbers of dehydrated cells containing high concentrations of hemoglobin. The total cell population showed a modest increase in potassium efflux, which may be reponsible for reduced cation content and dehydration in a subpopulation of cells. When the patients' red cells were separated into different density populations by centrifugation on density gradients, the cells of classic acanthocyte morphology were concentrated in the high-density layers. This was true for both patients, although the subject with acanthocytes and no clinical disorder had a normal red cell density distribution. Lipid analysis of both types of acanthocytes showed an increase in the relative proportion of sphingomyelin with respect to the glycerophospholipids. Total cholesterol and phospholipid levels were reduced in the chorea-acanthocytosis red cells, but the other acanthocytes did not differ significantly in total lipid content from normal control samples. Thus, the one common abnormal feature in these two forms of acanthocytosis is the increase in the proportion of red cell sphingomyelin. Because this is a very stable, immobile component of the membrane, we suggest that its relative enrichment could result from a defect in the transport and maintenance of glycerophospholipids. Further study of the dynamics of glycerophospholipid organization in acanthocytes may be useful in increasing our understanding of the genesis of abnormal, acanthocytic morphology.