Dehydrated hereditary stomatocytosis--a report of two families and a review of the literature.

Two families with an unusual type of congenital hemolysis characterized by a normal to high hemoglobin, high reticulocyte count, the presence of target cells or small irregular cells on the peripheral blood smear, and bowl shaped cells in hypotonic wet preparations are described. The underlying abnormality appears to be an increased membrane permeability to both Na+ and K+, with consequent alteration of total cell cation and water content. Seven families previously reported are also reviewed. The entity is currently known as hereditary stomatocytosis with hydrated and dehydrated subtypes, but the diagnosis is frequently overlooked because of the variable morphology of the red cells, often without obvious stomatocytosis.