[Nail psoriasis in individuals with psoriasis vulgaris: a study of 661 patients].

BACKGROUND AND OBJECTIVES The nails are affected in a substantial number of patients with psoriasis. Nevertheless, few epidemiological studies have reported the characteristics of patients with nail psoriasis. Here we describe the epidemiology of nail psoriasis and the main characteristics of affected patients. PATIENTS AND METHODS We undertook a prospective case-control study at Hospital Universitario Marqués de Valdecilla and Hospital Universitario Central de Asturias in Spain between January 2007 and December 2009. RESULTS Of a total of 661 patients included, 47.4% were diagnosed with nail psoriasis, which was 13.5% more prevalent in men. The group of patients with nail disease had more severe psoriasis (12.82 vs 8.22 points on the psoriasis area and severity index) and a longer disease duration (20.30 vs 13.94years), and included a larger percentage of patients with psoriatic arthritis (29.7% vs 11.5%), a positive family history of the disease (53.7% vs 42.8%), and a body mass index greater than 30 (31.6% vs 23.9%). A larger percentage of the patients with nail disease had early-onset psoriasis (74.1% vs 65.5%) and fewer were carriers of the human lymphocyte antigen Cw*0602 allele (33% vs 50.3%). CONCLUSIONS Nail disease is frequent in psoriasis and is associated with greater severity of psoriasis and a larger number of comorbidities.