Clinical utility of fluorometric scanning of plasma porphyrins for the diagnosis and typing of porphyrias.

The fluorometric emission scanning (using excitation at 405 nm) of plasma samples, simply diluted five-fold in phosphate-buffered saline, allows the differentiation of three conditions according to their porphyrin content. The emission maximum at 626-628 nm is a specific finding in variegate porphyria, while in erythropoietic protoporphyria a characteristic peak is found at 636 nm. A fluorescence emission maximum at 618-622 nm corresponds to a third group that includes normal subjects, non-porphyria patients and patients suffering from acute intermittent porphyria, hereditary coproporphyria, congenital erythropoietic porphyria (Günther disease) and porphyria cutanea tarda. Therefore, this simple, quick and cheap screening test allows one to establish whether a patient with a photocutaneous syndrome has porphyria and whether this porphyria belongs to the types: variegate, protoporphyria or other cutaneous porphyrias.