Classification and Evolution of Patterns of Erythropoiesis in Polycythemia Vera as Studied by Iron Kinetics

Abstract

1. Patients with polycythemia vera may be classified according to their erythropoietic pattern. Erythropoiesis is abnormally increased in all classes. Class I is characterized by normal red cell lifespan. Class II is characterized by shortened red cell lifespan; in Class IIa the shortened red cell survival is related to splenic sequestration of RBC; in Class IIb the markedly shortened red cell survival is predominantly related to intramedullary hemolysis. Class III is characterized by extramedullary erythropoiesis. Patients in Classes I and IIa are in relatively earlier phases of their disease and frequently are found to develop red cell kinetics of Class III as their disease progresses. Conversely, patients in Classes IIb and III are generally late in the course of their disease and have previous hematologic findings that suggest that they originally had the red cell kinetic patterns of Classes I and IIa. 2. As the duration of their disease increases, patients with polycythemia vera generally have a progressive shortening of red cell lifespan which is incompletely compensated by a progressive decrease in circulating red cell volume. However, total blood volume remains elevated since the plasma volume increases. These changes occur whether or not the patient receives radiation therapy. Similar changes may occur in white cell and platelet production and functional survival. It is suggested that the natural history of the disease may be characterized by progressive emergence of hematopoietic cell clones which have a selective advantage for reproduction associated with altered functional survival. 3. The results suggest the potential usefulness of iron, and occasionally of splenectomy, in selected polycythemic patients with myeloid metaplasia (Class III) and anemia, dependent upon the presence of the frequent finding of iron deficiency or the occasional finding of splenic sequestration of red cells in excess of splenic erythropoiesis.

The Relation of Thrombokinetics to Bone Marrow Megakaryocytes and to the Size of the Spleen in Polycythaemia Vera

“…The fact that there was a good relationship between megakaryocyte volume/ pl and effective platelet production in PV patients and the conformity of this relationship to control subjects suggests that there were no large individual variations in the total volume of erythropoietic marrow in the material analyzed. This is in agreement with the view of Pollycove et al (1966), Van Dyke et al (1968) and Wasserman (1971) that there is a normal skeletal distribution of the erythropoietic marrow in the early state of PV. Most of the patients in the present study were recently diagnosed and had a short duration of the disease (Table I).…”

Polycythaemia Vera: Differential Diagnosis by Ferrokinetic Studies and Treatment with Busulphan (Myleran*)

“…In the 22 cases described here, no correlation was noted between the elevated TRBC and the Hb or PCV. Our data and those of other workers indicate that the plasma volume may be normal, decreased or increased in polycythaemia Vera and this fact accounts for the lack of correlation between PCV and TRBC (Berlin, Lawrence and Gartland, 1950;Szur, Lewis and Goolden, 1959;Verel, 1961 ;Pollycove, Winchell and Lawrence, 1966).…”

Transitional Myeloproliferative Disorder

“…By contrast, the cases reported here have shown features of both PV and MF in a unique relationship which may be referred to as a transitional myeloproliferative disorder (TMPD). Pollycove et al(1966), in a review of ferrokinetic studies on 64 patients with PV, reported that 25 patients had surface counting evidence of extramedullary erythropoiesis in the spleen. In this group of PV patients which they labelled 'Type 111' there was a variable red cell production by the marrow with peripheral blood red cell values often lower than or within the normal range.…”