Spontaneous resolution of primary erythrocytosis in two girls

We report two girls with primary erythrocytosis in whom extensive diagnostic studies revealed no underlying cause. Normal growth of colonies derived from erythroid burst forming units (BFU-E) was observed, and serum erythropoietin concentrations were within or below the normal range. The absence of a rise in serum erythropoietin levels after isovolemic phlebotomy implicated the erythroid marrow as the site of the pathophysiologic abnormality in both patients. Spontaneous resolution of erythrocytosis occurred during the second decade of life. Our experience suggests that primary erythrocytosis may be self-limited in some children. In these cases, the proliferative abnormality may be sufficiently subtle as to not be detected by standard in vitro culture systems, which support the growth of colonies derived from erythroid progenitors.