New insight into the pathogenesis of nail psoriasis and overview of treatment strategies

Abstract

Psoriasis is a chronic inflammatory disease affecting up to 3% of the general population. The prevalence of nail involvement in psoriasis patients varies between 15% and 79%. While the nails represent a small portion of the body surface area, psoriasis in these areas can have a disproportionate influence on a patient's physical and psychosocial activities. Differential diagnosis between an onychomycosis and a psoriatic nail could be challenging; nevertheless, coexistence of onychomycosis and nail psoriasis also occurs and both are common disorders in the general population. Nail psoriasis can be difficult to treat. Treatment of nail psoriasis should consider the body surface area of skin disease, psoriatic arthritis, severity of nail disease, and the impairment in the quality of life. All patients should be tested for onychomycosis before starting a therapy. This recommendation is underlined by the fact that nail psoriasis is mostly treated by immunosuppressive drugs, like steroids, methotrexate, or biologics, which may aggravate mycotic nail infections. Conventional systemic therapy, such as use of steroids, cyclosporine, methotrexate, and retinoid in the long term, can cause organ toxicities. Currently, use of apremilast and tofacitinib favors an early healing of nail psoriasis because they act directly on the pathogenic targets, distressing the inflammatory signals associated with the initiation and maintenance of the disease activity, and as with several conventional synthetic disease modifying antirheumatic drugs, they are characterized by the convenience of oral administration. The number of treatment options has increased considerably in recent years; however, given the heterogeneity of the disease, the therapy should be personalized to individual cases.

Keywords: nail; onychomycosis; psoriasis.

Figure 1

The cytokines axis in psoriasis. IL-23-, IL-17-axis-related mediators are overexpressed in lesional psoriatic skin and nails. TNFα-/iNOS-producing dendritic cells (TiP-DCs) are activated by various cells and stimuli including Candida albicans. Candida activates Th17 and Th22 to produce IL-22 and IL-17A/F. Keratinocytes are the key-responding cells to this pathway. Abbreviations: VEGF, vascular endothelial growth factor; IL, interleukin; TNF, tumor necrosis factor; iNOS, inducible nitric oxide synthase; KC, keratinocytes.

Figure 2

Patient affected by nail psoriasis at baseline (week 0). The same patient after 12 weeks and 24 weeks of treatment with apremilast.