Prevalence, severity and clinical features of psoriasis in fingernails and toenails in adult patients: Italian experience.

Psoriasis is a chronic inflammatory skin disease affecting 2.0-6.5\% of the European population. Although the most striking clinical features of psoriasis involve the skin, other organs including nails and joints may be affected in a substantial proportion of patients. Literature reports nail involvement in 10-56\% of psoriatic patients, with common physical and social impairment. However, the precise prevalence of specific clinical features of nail psoriasis is somewhat under-reported.Our cross-sectional study aimed at describing the prevalence and the clinical features of nail involvement in adult psoriatic patients in a psoriasis referral centre in northern Italy.A total of 178 (124 men, 54 women) consecutive adult patients (≥18 years old) with psoriasis were included. Psoriasis Area and Severity Index (PASI) and Nail Psoriasis Severity Index (NAPSI) scores were calculated for each patient. Relevant medical history was recorded.Nail involvement was present in 137 (99 men, 38 women) patients (76.9\%). The most common nail abnormality was onycholysis, followed by crumbling, subungual hyperkeratosis, pitting and discoloration. Pitting and onycholysis were the most prevalent patterns observed in fingernails, whereas onycholysis and crumbling were the most frequent changes detected in toenails. The most frequently and severely affected nails were the fourth fingernail and the first toenail. The average PASI score was higher in individuals with nail involvement (12.0 vs. 8.7, P = 0.06). Nail changes were present in 85.7\% of patients with psoriatic arthritis.Our study confirms that nail involvement may be overlooked in psoriasis patients. Different psoriatic patterns in the nail affect specific digits more frequently.