Excess erythropoieten may be removed from the blood by a process called chelation, or it may be done in a blood bank where units of red blood
are removed, leaving the rest of the blood
in tact. Not a dangerous proceedure, but I have never heard of this being done on children under 10yrs. Conditions that cause this may include heart disease, pulmonary fibrosis (both bad things), or it may be hereitary in nature and have no cause.