[Nail psoriasis-painful and yet undertreated : From pathogenesis to therapy].

Nail psoriasis (NP) affects approximately 50% of psoriasis patients and is a common but often oversee disease feature that correlates with the duration and severity of psoriasis. The pathogenesis of NP is dominated by the increased expression of inflammatory cytokines such as interleukin (IL)-23 and IL-17, which leads to painful inflammation and hyperkeratosis in the nail apparatus. Clinically, there are changes to the nail matrix and the nail bed, usually characterized by spotty nails and distal onycholysis. In addition, psoriatic arthritis is more common in patients with NP. Patients with NP have a higher reduction in health-related quality of life and a higher comorbidity profile than psoriasis patients without NP. Various scores such as the Nail Psoriasis Severity Index (NAPSI) and the Physician's Global Assessment of Fingernail Psoriasis Score (f-PGA) or the Nail Assessment in Psoriasis and Psoriasis Arthritis (NAPPA) are available for the objective assessment of severity, whereby the latter also takes subjective symptoms into account. In terms of differential diagnosis, onychomycosis or its coexistence should always be considered when making the diagnosis. The severity-adapted treatment of NP is often extremely protracted. Overall, there are only a few studies on topical or systemic traditional therapy. Significantly more and promising data are available on the use of biologic therapies, which are often recommended for the primary treatment of NP, particularly in cases of nail matrix infestation.