Can primary polycythemia have normal to high epo level

my 15yr old son is being treated by weekly phlebotomy has had mri of kidney,liver,spleen,arterial blood gas normal,cleared by cardiologist&pulmonologist.high hct&red blood cell count but no low epo(runs normal to high)symptons:2 yrs of low iron levels,extreme fatigue,dizziness,blind spots in vision,itchness when hot, chest pain&difficulty breathing with exercise. After a month of phlebotomy symptoms are all but gone. hct in normal range this week.what could cause secondary if no tumors were found?? Can it be primary w/o low epo?? please any info would be greatly appreciated.Thanks