Leukocyte colony‐forming cells in the peripheral blood of children with hereditary spherocytosis

Increased numbers of committed leukocyte precursor cells were observed in the peripheral blood of children with hereditary spherocytosis in a study that made use of the in vitro leukocyte colony‐forming technique. Five children with hereditary spherocytosis had increased numbers of peripheral blood colony‐forming unit cells (CFUc) before splenectomy (range 8.7‐27.2 CFUc/10 6 cells/plate; normal range 0‐5 CFUc/10 6 cells/plate), but no CFUc were found 24‐120 hours after splenectomy. Six additional cases of hereditary spherocytosis (presplenectomy) had increased CFUc in their peripheral blood (range 7.5‐61.3 CFUc/10 6 cells/plate). Three patients with other hemolytic anemias associated with increased hematopoietic activity also had increased peripheral blood CFUc values. Five cases of hereditary spherocytosis were studied two or more months after splenectomy and generally had normal numbers of CFUc in their blood (range 0‐6.4 CFUc per 10 6 cells/plate). In all spleens there was evidence of extramedullary hematopoiesis. Four patients with elliptocytosis and one patient with hereditary spherocytosis, all with intact spleens, had normal numbers of peripheral blood CFUc. These studies document increased peripheral blood CFUc in hereditary spherocytosis with hemolytic anemia of moderate severity and implicate the degree of hematopoietic stress as a factor in the regulation of increased CFUc emerging from the bone marrow in these patients. As an indicator of hematopoietic stress, an elevated reticulocyte count may reflect to some degree the presence of increased CFUc circulating in the peripheral blood of unsplenectomized hereditary spherocytosis patients.