porphyrias
Porphyrias refer to a group of uncommon inborn or acquired disturbances of porphyrin metabolism.
Porphyrins are pigments normally present in hemoglobin, myoglobin, and cytochromes.
The classification of porphyrias is based on both clinical and biochemical features. The five major types are:
(1) congenital erythropoietic porphyria
(2) erythrohepatic protoporphyria
(3) acute intermittent porphyria
(4) porphyria cutanea tarda
(5) mixed porphyria
Minor types
Cutaneous manifestations consist of urticaria and vesicles that heal with scarring and that are exacerbated by exposure to sunlight. The primary alterations by light microscopy are a subepidermal vesicle with associated marked thickening of the walls of superficial dermal vessels.
The pathogenesis of these alterations is not well understood, although serum proteins, including immunoglobulins, typically form glassy deposits in the walls of superficial dermal microvessels.