L’ongle et l’os psoriasiques

Abstract

Nail involvement in psoriasis is the most frequent at this anatomic site. Nail psoriasis can occur in the setting of diffuse or localized skin involvement, of arthritis, or can be strictly isolated. Prevalence of nail psoriasis is probably underestimated since all clinical features are unknown from physicians. When considering nail involvement, dermatologist plays a key-role in the diagnosis of early psoriatic arthritis. The (second for the thumb) third phalanx is a key bone since the nail is anatomically linked by fibrous structures, and such an enthesis is the target for inflammatory processes occurring in both psoriasis and psoriatic arthritis. Enthesitis is considered as a bridge between nail and bone. Psoriatic arthritis is clearly associated to nail involvement, in particular in clinicopathological presentations such as distal interphalangeal arthritis, Bauer finger at the finger and onychopachydermoperiostosis at the toe. In other types of spondylarthropathies, and in psoriatic arthritis, nail involvement is a major clinical feature for diagnosis and classification included in CASPAR criteria.