Quantitative measurements of the erythropoietic activity of the marrow, of circulating red cell production and destruction have been made in patients with pernicious anemia in relapse and during response to vitamin B12 therapy.

Total erythropoietic marrow activity as reflected by turnover of heme components proceeds at a rate of approximately 3 times normal. The delivery of viable red cells to the circulating blood, however, does not increase above normal. This would indicate that the greater portion of marrow activity is ineffective in terms of blood production. This marrow dysfunction coupled with an increased rate of cell destruction of approximately 3 times normal is responsible for the anemia. Total erythropoiesis is somewhat less, and effective erythropoiesis considerably less, than that which may be expected of the normal marrow under the sustained stimulus of anemia.

The reticulocyte count is shown to be an unreliable index of blood production in untreated pernicious anemia due to loss of reticulum from cytoplasma of many red cells before their delivery into circulation.

During the response to vitamin B12 the ineffective erythropoiesis is converted to effective erythropoiesis, whereas total erythropoiesis remains unchanged. The rate of blood production during recovery is 3 to 4 times normal.

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