PORPHYRIA is a relatively rare, inherited fault of pyrrole metabolism which produces a wide variety of clinical symptoms from time to time or remains latent for years or for life. It is characterized by the excretion of abnormal kinds and amounts of porphyrins, chiefly uroporphyrin and its precursors. The condition also is manifested in certain domestic animals as photosensitivity.
This concept of porphyria must be modified to some extent in the light of recent discoveries. Abnormal excretion of porphyrin is increased in cases of lead poisoning. Furthermore, porphyria of two distinct types has been induced in laboratory animals by administration of phenylhydrazine, lead and ultraviolet light on the one hand, and by allylisopropylacetylcarbamide (Sedormid) on the other. These two experimental forms are similar in many respects to the main types which occur naturally in human beings, namely, the erythropoietic and the hepatic.
The older classifications of porphyria into congenital, acute,