A number of different genetic defects may cause spherocytosis, all of which have in common the production of a faulty protein component of the cell membrane. The faulty component leads to the weakness of the red blood cell wall.
In addition to being fragile, these red blood cells are less resistant to stress and rupture easily.
In some rare cases, spherocytosis is not inherited; the cause of this blood disease is considered to be a spontaneous mutation of the gene. Infection, fever and stress can stimulate the spleen to destroy more red blood cells than usual. If this occurs, the skin and whites of the eyes will turn yellow because the hemoglobin level will drop and the bilirubin level will rise. Bilirubin is a chemical made when red blood cells are destroyed.