Congenital Hemolytic Anemia Associated with Dehydrated Erythrocytes and Increased Potassium Loss

A 21-year-old woman was found to have congenital hemolytic anemia characterized by dehydrated-appearing erythrocytes in the peripheral blood. The red-cell sodium was increased, potassium was decreased, and the cell water content was reduced. No metabolic or hemoglobin abnormalities were detected to account for this cation distribution. The basic defect appeared to be increased membrane permeability to cations that was greater for potassium than for sodium. Consequently, these cells lost potassium in excess of sodium gained, the total cell cation content decreased, and rigid, osmotically resistant desiccytes (dehydrated erythrocytes) were formed as water left the cells in response to the decreased solute concentration. Clinically, this patient has done well in spite of persistent hemolysis. Her three-year-old son also has congenital hemolytic anemia with the same clinical abnormalities, including a marked decrease in red-cell potassium. Whereas previous studies have demonstrated that permeability abnormalities can lead to water-loaded cells and hemolysis, our findings indicate that cellular dehydration may also produce hemolytic anemia. (N Engl J Med 291:491–496, 1974)