Erythropoietic protoporphyria: evidence for multiple sites of excess protoporphyrin formation

A patient with erythropoietic protoporphyria was studied to determine the sites of excess protoporphyrin formation. The patient's protoporphyrin was pulse labeled by the simultaneous administration of the precursors 2-glycine-(14)C and 3,5-delta-aminolevulinic acid-(3)H; delta-aminolevulinic acid preferentially labels the hepatic pool. Blood and feces were studied at intervals for the next 14 days. Protoporphyrin was extracted from erythrocytes, plasma, and feces, identified by thin-layer chromatography, and quantitated spectrophotometrically, and its specific activity was determined by liquid scintillation spectrometry. Analysis of the kinetic and isotopic data indicated at least two sources of protoporphyrin, one localized in the erythroid cells, a second in the liver. The liver was responsible for the majority of the excess protoporphyrin. This report thus provides evidence of a genetic porphyria exhibiting an abnormality of porphyrin biosynthesis in at least two tissues. We propose that the disease, erythropoietic protoporphyria, be renamed erythrohepatic protoporphyria.