A condition in which the passive leakage of ions across the erythrocyte plasma membrane is increased, leading to shortened cell survival, increased osmotic fragility, and haemolytic anaemia. The cells take on an abnormal shape, resembling a mouth or ‘stoma’. In hereditary stomatocytosis I (overhydrated stomatocytosis) there is variation in the extent of sodium influx and osmotic swelling and three subtypes with marked, moderate, and normal sodium influx have been suggested. There appears to be a defect in stomatin, although the aetiology is still obscure. A second form, stomatocytosis II, in which there is no increase in fragility, has been reported. A different disorder, dehydrated hereditary stomatocytosis (xerocytosis; desiccytosis), is caused by excessive leakage of potassium from the erythrocytes which lose water and become more fragile.
Subjects: Medicine and Health.