Nail involvement features in palmoplantar pustulosis.

Pathogenesis of palmoplantar pustulosis (PPP) is not fully understood and whether PPP is a variant of plaque psoriasis (PsO) is still controversial. Psoriatic nail changes are among the clinical features common to both diseases, and understanding them could lead to the understanding of the correlation between both diseases. However, only limited numbers of studies have reported nail involvement pattern in PPP. In this study, we conducted a retrospective review of the medical records and photographs of patients diagnosed with PPP to understand the nail involvement features in PPP patients. We compared the results with the data from our previous study that analyzed the pattern of nail involvement in PsO. As a result, nail involvement was observed in 66.3% of the patients and its severity was correlated with the severity of cutaneous lesions (r = 0.34, P = 0.01). Onycholysis and crumbling were more frequent in PPP than in PsO. Crumbling was associated with higher severity of PPP (P = 0.01), while onycholysis was associated with lower severity (P = 0.03). In PPP, nail changes in the first digits were less prominent than those in other digits when compared with PsO. Risk factors for nail involvement in PPP included female sex (odds ratio [OR] = 9.44, P < 0.001), younger age at diagnosis (OR = 1.08, P = 0.01), and higher severity (OR = 1.15, P = 0.01). Presence of psoriatic arthritis did not show significant association with nail involvement (OR = 1.62, P = 0.77). In conclusion, although PPP shares some nail features with PsO, differences were noted in the commonly observed features and in the distribution of involved nails.