Identification of nail features associated with psoriasis severity.

There are no detailed studies of the prevalence of nail psoriasis and clinical characteristics of psoriatic nail involvement, including nail features associated with disease severity. Therefore, we designed a study to investigate the prevalence and characteristics of psoriatic nail involvement in patients with psoriasis and determine the relationship between psoriatic nail features and severity of nail psoriasis and cutaneous psoriasis. The Nail Psoriasis Severity Index (NAPSI) was used for evaluation of the severity of nail lesions. The presence of nail fold psoriasis (NFP) was also assessed. The severity of psoriasis was evaluated by calculating the Psoriasis Area and Severity Index (PASI). As a result, the prevalence of nail psoriasis was 85.5%. Pitting was the most common clinical feature (55.6%). The severity of nail psoriasis was not affected by medical parameters, although patients with localized pustular psoriasis tended to have more severe nail psoriasis than did those with chronic plaque psoriasis. When comparing the mean NAPSI and the mean PASI according to nail lesions, we found that subungual hyperkeratosis (SH) and NFP were significantly associated with the severity of both nail psoriasis and cutaneous psoriasis. Psoriatic nail changes were most common in the first digit. Conclusively, the majority of patients with psoriasis had psoriatic nail involvement, and Koebner's response seems to be closely related to the induction of nail psoriasis. To limit progression of the disease, psoriatic patients with SH or NFP should be examined thoroughly because those clinical features reflect the levels of severity of both nail and cutaneous psoriasis.