Stomatocyte. Illustration of a stomatocyte, an abnormal red blood cell in hereditary stomatocytosis. This disease arises from a dominant genetic defect in red blood cell membranes. These cells leak sodium and potassium ions, lose their normal indentation on one side forming a mouth-like shape (stoma), and eventually burst. This results in haemolytic anaemia and sometimes clotting problems. There is no specific treatment, but blood transfusions may sometimes be required.