porphyria

1. (pathology) Any of several usually hereditary abnormalities of porphyrin metabolism characterized by excretion of excess porphyrins in the urine.Examples: "The term porphyria, derived from the Greek word porphyra, meaning purple, is apt because a hallmark of most of the porphyrias is the overexcretion of porphyrins in urine or feces."; "However, the appearance of homozygous forms without consanguinity and coincidence of two types of porphyria in the same patient, dual porphyrias, is possible."; "The usual presenting symptoms and signs of porphyrias are either skin photosensitivity or neurovisceral symptoms and signs."