caused by a clonal expansion of a multipotent myeloid stemcell that primarily
produces extra erythrocytes.
polycythemia refers to increased red cell mass due to compromised
abil-ity of blood to supply oxygen to tissues. Causes include chronic
obstructive pulmo-nary disease and cyanotic congenital heart disease.
Erythropoietin levels can be appropriately high. Secondary polycythemia may
also be caused by inappropriately high erythropoietin levels, with renal cell
carcinoma excreting erythropoietin being the typical cause.
Relative polycythemia refers
to an increased red cell count secondary to decreasedplasma volume (typically
due to dehydration). Red cell mass, erythropoietin, and blood oxygen content