The porphyrias: recent advances.

Recent research has elucidated several of the hitherto poorly understood steps in heme synthesis. This review describes this metabolic pathway and pinpoints the enzymatic blockages in the various porphyrias. Recent advances in the understanding of the etiology of porphyria cutanea tarda are discussed, as are the abnormalities of porphyrin metabolism seen in chronic renal failure and in lead poisoning. An outline is given of the clinical and biochemical abnormalities seen in the porphyrias. Included is an algorithm to aid in the differential diagnosis of these diseases, and a brief review of the new analytical techniques available for the identification and quantification of porphyrins and their precursors in body fluids.