Photoprovocation test and immunohistochemical analysis of inducible nitric oxide synthase expression in patients with Sjögren's syndrome associated with photosensitivity.

Abstract

Annular erythema (AE) in Sjögren's syndrome (SS) usually develops on areas of sun-exposed skin and is exacerbated during summer. To evaluate photosensitivity in SS and to investigate the involvement of ultraviolet (UV) radiation in the development of AE in SS. Phototesting with UVA and UVB was performed on 14 SS patients, including 10 with primary SS. Clinical and histological features as well as expression of inducible nitric oxide synthase (iNOS) in the evoked skin lesions were compared with those of lupus erythematosus (LE). Eleven SS patients had a history of photosensitive AE (n = 4), papules (n = 3) or other types (n = 4) of lesions on their sun-exposed skin that were induced or aggravated by sunlight exposure. Phototesting induced a prolonged erythematous response (n = 8), infiltrated erythema (IE) (n = 4) and/or papules (n = 3) in 11 of 14 SS patients, including one with primary SS without a history of photosensitivity. Histologically, the induced IE and papules showed coat-sleeve-like or sparse perivascular infiltration of lymphocytes similar to that in primary skin lesions of AE in SS. No epidermal changes characteristic for LE were found except for partial and mild liquefaction degeneration in three cases. In contrast, two cases were indistinguishable from the papular type of polymorphic light eruption in several aspects, including their primary skin lesions and early response to a photoprovocation test. Immunohistochemistry revealed diffuse expression of iNOS throughout the epidermis, which is characteristic for LE, in the three SS patients with minimal liquefaction degeneration, while the remaining seven SS patients examined exhibited no iNOS staining or a normal expression pattern. Our results indicate that photosensitivity exists in certain primary SS patients, and that UV is critical to the development of AE in SS, probably through a pathological mechanism distinct from that in LE.