A family of hereditary stomatocytosis associated with normal level of Na+-K+-ATPase activity of red blood cells.

A rare familial case of hereditary stomatocytosis with hemolytic anemia, increased autohemolysis, increased osmotic fragility, and shortened erythrocyte survival is described. The erythrocytes were abnormally permeable to sodium and potassium. In addition, "Na-K pump" rate of the red blood cells was increased, while Na+-K+-ATPase, Mg2+-ATPase and Mg2+-Ca2+-ATPase activities were within normal limits. Splenectomy induced marked improvement of anemia.