Mouse model for protoporphyria. III. Experimental production of chronic erythropoietic protoporphyria-like skin lesions.

Albino mice were made protoporphyric with griseofulvin according to an established procedure. Photosensitivity flares were elicited once a week throughout a 10-month period, using black light as a source for 410 nm radiation and the flares were monitored by the intravenous injection of vascular tracers and by light and electron microscopy. Each irradiation led to a selective destruction of the endothelial cells of superficial capillaries which was followed by massive vascular leakage. The basal lamina remained largely intact, providing the scaffold for regenerating endothelial cells which deposited new basal lamina material at their periphery. Subsequent exposures to 410 nm radiation reproduced the endothelial damage and subsequent basal lamina formation; multiple irradiations thus resulted in excessive, concentric, tubelike basal lamina deposits around dermal vessels which light microscopically appeared as PAS-positive hyaline material and clinically gave the skin a thickened, waxy appearance. This model thus reproduced the skin of erythropoietic protoporphyria clinically, microscopically, and at the ultrastructural level.