Pemphigus foliaceus induced by exposure to sunlight. Report of a case and analysis of photochallenge-induced lesions.

BACKGROUND

Although there are many reports on photo-induced pemphigus, careful analysis in the development of acantholytic blister have rarely been performed in the lesions induced by photochallenge.

OBJECTIVE

The study was intended to elucidate the mechanisms by which ultraviolet light (UV) radiation causes the skin lesions of pemphigus foliaceus.

METHODS

Photochallenge-induced lesions were examined histologically and immunohistochemically over the time course with three biopsy specimens. Neutrophil adhesion assay was performed using the specimens prepared from the photochallenged lesions as substrates.

RESULTS

A small number of neutrophils were seen at 5 h after photochallenge in the dermis and epidermis, and slight acantholysis was detected at 72 h. In neutrophil adhesion assay, greater numbers of neutrophils adhered to the upper epidermis of the skin obtained at 5 h after challenge.

CONCLUSIONS

Our results suggest that both enhanced binding of autoantibodies to the epidermis after UV radiation and preferential adhesion of neutrophils to the UV-irradiated epidermis contribute to the development of acantholysis in photo- induced pemphigus foliaceus. Intercellular adhesion molecule-1 (ICAM-1) expression on keratinocytes is not primarily responsible for the epidermal migration of neutrophils.