The Porphyrias 1995-98 Dr. Maged Nabih Kamel. All rights reserved. The photosensitivity of the skin in porphyria is due to porphyrins absorbing ultraviolet radiation in the 400 nm range and emitting an intense red fluorescence. Porphyrins, when irradiated with light of the appropriate wavelength in the presence of oxygen, will cause photodynamic effects.
Light energy absorbed by the porphyrin raises electrons into an excited state.
In areas of sclerosis, the collagen bundles are thickened. It is quite characteristic of the bullae of porphyria cutanea tarda that the dermal papillae often extend irregularly from the floor of the bulla into the bulla cavity. This phenomenon referred to as festooning , is explained by the rigidity of the upper dermis induced by the presence of eosinophilic material within and around the capillary walls in the papillae and the papillary dermis. There is no or just a minimal inflammatory cell infiltrate in the dermis. Proof that the perivascular material in porphyria represents excessively synthesized basement membrane material and as such contains type IV collagen is provided by positive immunofluorescence staining with anti-type IV collagen monospecific antibody.