A classification of polycythemia and three cases of demonstrating increased red cell mass are presented.
Polycythemia may be relative or absolute, secondary to underlying disease, or an idiopathic dyscrasia of hematopoiesis. Accurate measurement of blood, red cell, and plasma volumes are essential to differentiate relative and absolute polycythemia. Dilution techniques may be misleading, due to escape of label from vascular spaces or differences between whole-body and venous hematocrits. Red-cell labeling offers a more precise method to differentiate between relative and absolute polycythemia but is not helpful in distinguishing primary from secondary causes.
Hypoxia-sensitive receptors may mediate erythropoietin production where relative tissue anoxia exists for any reason. Certain tumors (benign and malignant), chemical agents, and physical factors also stimulate an increase in red cell mass, often through increasing elevation of erythropoietin.
Erythropoietin levels (bioassay) are usually not demonstrably elevated in polycythemic states, since erythropoietin is constantly utilized in erythropoiesis. High levels are often seen with marrow aplasia and may be demonstrable in cyst fluid of erythropoietin-producing tumors. In addition to existing erythropoietin assay procedures, methods for determining turnover are badly needed. Biochemical, electrophoretic, molecular weight, and antibody neutralization studies suggest the similarity or sameness of tumor-produced and naturally occurring erythropoietin.
Polycythemia rubra vera erythremia occurs more commonly in Caucasians and especially among Jewish peoples of Eastern European origin. Frequent symptoms are fatigue, dizziness, headache, and pruritus. Patients often seek care with symptoms related to peptic ulcer, varicose veins, gouty arthritis, and thrombotic episodes. Physical findings include plethora, splenomegaly, and, in 25% of cases, hepatomegaly as well as those associated with the complications. Elevation of packed cell volume, white cell and platelet counts, as well as elevated red cell mass are usual in erythremia.
Proper hematologic control, with lessening of symptoms and complications, depends upon on-going evaluation as well as on phlebotomy and myelosuppression, as indicated. Controversy still exists as to optimal mode of myelosuppression.