How the Red Cells Become Sphericle in Hereditary Spherocytosis?

The cells of hereditary spherocytosis are more permiable to sodium. As a result more sodium come in the cells. Water also find its way in to the cells down the osmotic gradient created by sodium influx. Influx of sodium irons also occurs in normal cells too, but the sodium potassium ATPase pump manage to send the excess sodium out of the cells. In hereditary sperocytosis, these this pump is overloaded, because the pump requires ATP to continue its function. The cell cannot provide enough ATP to meet this demand. As a result the cell cannot pump out all the sodium that comes in to the cell. Finally, water accumulates within the cell causing it to swell and become spherocytes.