In psoriasis treatment, greater improvement in skin severity predicts greater improvement in nail severity

Nail are important for both function and esthetic appearance and although they represent a small body surface area, dermatologic disorders affecting the nails can have a detrimental effect to the patient. Deciding on the best systemic antipsoriatic drug to treat nail psoriasis can be difficult due to the lack of nail data on their Food and Drug Administration-approved labels, as well as the variety of scoring systems used for nail psoriasis.

We performed a literature review and included randomized control trials or articles based on randomized control trials for different systemic antipsoriatic drugs. Only articles and studies utilizing Nail Psoriasis Severity Index (NAPSI) or target NAPSI as outcome measures were included. Data was taken directly from articles, directly from clincaltrials.gov or directly from data on file at various pharmaceutical companies.

Data for NAPSI and PASI were collected for 10 antipsoriatic drugs including three oral medications and seven biologic agents. We found that NAPSI or target NAPSI was strongly predicted based on the change in PASI and duration of treatment (R = 0.71, p = .0002). PASI alone (R = 0.52, p = .001) and duration alone (R = 0.21, p = .07) predict NAPSI response.

According to this model, there is a relationship between skin and nail response, with improvement in nails correlating with improvement in skin and longer duration of treatment.