Stomatocytes are erythrocytes with a slit-like central pallor. Otherwise, they resemble typical RBC's in size and shape. Unless 10% or more of the RBC's are stomatocytes, their presence is probably artifactual.

• Stomatocytes form at a low blood acidic pH as seen in exposure to cationic detergents, and in patients receiving phenolthiazine.
• Hereditary stomatocytosis has some resemblance to hereditary spherocytosis, as stomatocytes may develop into spherocytes with further metamorphosis.
• In hereditary stomatocytosis, mild anemia and findings of on-going hemolysis should be evident if the condition presents as a clinical problem at all.