Abstract BACKGROUND: Psoriasis is a disease of worldwide distribution with a prevalence of 1 to 3%. Nail psoriasis is estimated in 50% of patients with psoriasis, and in the presence of joint involvement, it can reach 80%. OBJECTIVE: To study the nail changes - and their clinical implications - presented by patients with psoriasis vulgaris under surveillance in a university hospital from the south of Brazil. METHODS: his cross-sectional study evaluated 65 adult patients from January 2012 to March 2013. Cutaneous severity was assessed according to the Psoriasis Area and Severity Index (PASI). The Nail Psoriasis Severity Index (NAPSI) was used to evaluate patient's nails. The diagnosis of psoriatic arthritis was established according to the Classification Criteria for Psoriatic Arthritis (CASPAR). RESULTS: The prevalence of NP was 46.1%. These patients had a median [interquartilic range (IQR)] NAPSI of 1 (0-15). A total of 63.3% of patients reported aesthetic discomfort or functional impairment related to their nails. Onycholysis was the most common feature (80%). When compared with patients without nail involvement, patients with NP had lower mean age at psoriasis onset [21 (18-41) vs. 43 (30-56) years, p=0,001]; longer disease duration [15.5 (10-24) vs. 6 (2-12) years, p=0.001]; higher PASI [9.2 (5-17) vs. 3.7 (2-10), p=0.044], higher frequency of psoriatic arthritis (43.3 vs. 3.7, p = 0.002) and more often reported family history of psoriasis (40% vs. 7.4%, p = 0.011). CONCLUSION: Onycholysis was the most frequent finding and most patients feel uncomfortable with the psoriatic nail changes that they experience.

Nails are considered epidermal appendages, and as such, are commonly affected in patients with psoriasis, 80% of whom are likely to develop nail psoriasis as a result of their condition. Two patterns of nail disorders have been shown to be caused by psoriasis. Nail matrix involvement can result in features such as leukonychia, pitting (punctures or cupuliform depressions), red spots in the lunula and crumbling. Nail bed involvement, on the other hand, can cause onycholysis, salmon or oil-drop patches, subungual hyperkeratosis and splinter hemorrhages. Nail disease causes aesthetic and functional impairment, and is indicative of more severe forms of psoriasis as well as of joint involvement. The treatment for nail psoriasis involves behavioral interventions, topical medications, or systemic therapy in case of extensive skin or joint involvement. This article presents a review of the main features of nail psoriasis, its clinical presentation, diagnostic and assessment methods, clinical repercussions, and of its available treatment options.