Repression by hematin of porphyrin biosynthesis in erythrocyte precursors in congenital erythropoietic porphyria.

Hematin administered intravenously in a patient with congenital erythropoietic porphyria evidently entered erythrocyte precursors in the bone marrow, producing the well-known negative feedback repression of porphyrin biosynthesis with marked decline of porphyrin concentrations in urine, circulating plasma, and erythrocytes. A delay in the major segment of this effect corresponded roughly with the sum of the average transit times through the maturation compartments of the erythrocyte precursors. This delay was considerably longer than previously observed in the decline of porphyrin precursors after administration of hematin in patients with hepatic porphyria. The effect of hematin was compared with that of packed erythrocyte transfusions given at regular intervals in the same patient over a period of 2.5 years. In general, administration of hematin results in a reduction of porphyrin formation of the same order of magnitude, but of shorter duration, possibly in relation to the relatively small amounts of hematin infused.