Nail psoriasis is considered one of the six disease domains of psoriatic arthritis (PsA) and may precede the disease by many years. The prevalence of nail disease in patients with PsA ranges from 41% to 93%, and imaging studies have indicated a close link between nail psoriasis and enthesitis, a hallmark manifestation of early PsA that can lead to structural changes, pain, and disability. Although nail psoriasis is an important feature of PsA, real-world studies that have examined characteristics of patients with PsA and nail psoriasis, particularly in the United States, are limited. For a real-world study published in The Journal of Rheumatology, my colleagues and I sought to examine the association of nail disease with patient demographics, disease activity, quality of life (QOL), and work productivity among patients with PsA.

Comparing Patients by Nail Psoriasis Presence
This cross-sectional study included all patients aged 18 or older enrolled in the US-based Corrona PsA/Spondyloarthritis Registry between March 21, 2013 and October 1, 2018 with a diagnosis of PsA who had non-missing data for physician-reported nail psoriasis at the enrollment visit. Patients were stratified by presence versus absence of physician-reported nail psoriasis at the time of enrollment, defined as a nonzero response on the nail psoriasis visual analog scale (VAS) of 0-100. Descriptive analyses of patient demographics, disease activity, QOL, and work productivity were assessed at enrollment and compared between nail psoriasis groups using t tests or Wilcoxon rank sum tests for continuous variables and χ2 or Fisher exact tests for categorical variables.

Of the 2,925 patients with PsA enrolled between March 2013 and October 2018, 2,841 had information available about the presence of nail psoriasis at registry enrollment and were included in the analysis, among whom 1,152 had nail psoriasis (prevalence, 40.5%). Prior to registry enrollment, the majority of patients (68.7%) were biologic naïve. Patients with nail psoriasis were slightly younger (mean age, 53.1 vs 54.4) and more likely to be male (51.9% vs 44.1%) compared with patients without nail psoriasis (both P <0.01). Patients with nail psoriasis were also more likely to be disabled from working due to their disease (12.3% vs 7.8%; P <0.01 for distribution across work status category) and had a history of depression (17.8% vs 13.3%; P <0.01) compared with patients without nail psoriasis. Symptom duration, disease duration, and prior and current medication use were comparable in patients with versus without nail psoriasis. Impacts of Nail Psoriasis
Overall, patients with nail psoriasis had higher disease activity at enrollment than those without nail psoriasis. Patients with nail psoriasis had a significantly higher mean percentage of affected body surface area (7.9% vs 3.5%), tender joint count (6.0 vs 3.5), and swollen joint count (2.4 vs 1.7), as well as worse mean composite measures of disease activity, than patients without nail psoriasis (all P <0.01). Patients with nail disease were less likely to be in minimal disease activity (35.0% vs 47.6%) and had an increased prevalence of enthesitis (27.7% vs 17.0%) and dactylitis (12.2% vs 7.4%) compared with those without nail psoriasis (all P <0.01).

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Patients with nail psoriasis also had overall worse health-related QOL than patients without nail psoriasis. Patients with nail psoriasis reported higher mean pain (41.7 vs 36.1) and fatigue (43.9 vs 39.0) scores on a visual analog scale (range, 0-100) than those without nail psoriasis (all P <0.01; Table). In addition, patients with nail psoriasis had worse physical function and overall health state, as well as greater work productivity and activity impairment, than those without nail psoriasis.

The Importance of Identification & Management
Overall, our results highlight the burden of nail psoriasis in patients with PsA. Nail psoriasis was associated with greater severity of psoriasis and PsA symptoms, more disability and functional impairment, and worse health-related QOL. These findings emphasize the importance of identification and management of nail disease in patients with PsA. Further research is needed to assess whether nail disease affects treatment response in patients with PsA.