Relative Polycythemia—The Polycythemia of Stress *

In a group of normal subjects going from sea level to approximately 16,000 feet we observed that very soon after arrival at high altitude there was hemoconcentration, as indicated by an increased red cell count and hematocrit, but a normal total red cell volume and a low plasma volume. This "apparent increase" in the number of red blood cells in the early days after arrival at high altitude is, of course, replaced by a real increase in red blood cells or an altitude polycythemia after the subject remains at altitude for longer periods of time, since altitude anoxia stimulates red cell production.6 At sea level we have observed patients referred to us with a probable diagnosis of polycythemia vera who have the same picture with reference to the red cell count and blood volume. These individuals have increased red cell counts and hematocrits, but normal total red cell volumes and decreased plasma volumes.2 Although nearly all of these subjects have lived and are living at sea level or near sea level, it is our belief that they exhibit a relative polycythemia due to hemoconcentration possibly brought about by various forms of stress other than anoxic stress. In a series of 215 patients with elevated red cell counts, approximately 175 had polycythemia vera where there was a real increase in total red cell volume.5 Twenty-two had polycythemia with increased total red cell volumes secondary to pulmonary or cardiac disease, and the remaining 18 (the subject of this paper) were patients exhibiting an increased red cell count and hematocrit but having a normal total red cell volume and a decreased plasma volume. In the following discussion of these patients we refer chiefly to the 17 out of the total 18 who had no other associated organic pathology. In one female patient (#15) the finding of relative polycythemia was associated with multiple myeloma.