Histogenesis of UV light-induced blister formation.

Histological examination of ultraviolet light (UVL)-induced blister formation in guinea pig skin is reported. Light and electron-microscopic examination was performed on skin exposed to single and multiple exposures of a large dose of UVB. In light microscopy, intracellular edema was prominent, especially in the lower part of the epidermis, where it developed into a blister. It seemed to be a subepidermal bulla. The PAS-positive basement membrane was observed at the floor of the blister. The positive Nikolsky's sign seemed to be due to a separation between the degenerated and regenerated epidermis. Electron microscopy revealed a marked intercellular as well as intracellular edema and well-preserved desmosomes. The basal lamina was always located at the floor of the blister. The difference in UVL-induced blister formation between normal and pathological conditions is discussed.