Weber1 divided cases of polycythemia into three groups: (1) relative polycythemia due simply to concentration of the blood; (2) secondary polycythemia due to high altitude, cardiopulmonary disease, blood stasis in other organs or toxemia, such as poisoning by phosphorus, and infectious diseases and (3) true erythremia due to primary idiopathic excessive erythroblastic activity in the bone marrow.
Polycythemia vera (erythremia, Vaquez' disease or Osler's disease) has been defined as a "morbid condition, characterized by a well marked, persistent relative and absolute polycythemia, due to an excessive erythroblastic activity of the bone marrow which appears to be the primary morbid factor." As to the agent or mechanism responsible for this disturbed function of the bone marrow, there is only speculation. Osler suggested that eventually all types of polycythemia would be found to be secondary. Even if this proves to be correct, it may be assumed that the polycythemia in some cases
BARKER NW. POLYCYTHEMIA VERA AND CHRONIC PULMONARY DISEASE. Arch Intern Med (Chic). 1931;47(1):94-103. doi:10.1001/archinte.1931.00140190105010