Epidemiology and Severity of Prurigo Nodularis in Europe: A Literature Review with an Application to Italian Data

Introduction: Prurigo nodularis is a chronic inflammatory skin disease with recent definition and relatively low prevalence. Information on prurigo nodularis, including its epidemiology, severity, and burden of disease, is still scanty. Objectives: We sought to review and summarize recent quantitative data on prurigo nodularis in Europe and to estimate the burden of disease in Italy, with a focus on moderate-to-severe prurigo nodularis. Methods: We conducted a systematic literature review of recent studies on the epidemiology of prurigo nodularis in Europe, using PubMed/MEDLINE and EMBASE. The study selection process was conducted independently by two reviewers. Articles focusing on the severity of prurigo nodularis were also searched (non-systematically), and relevant information was extracted. Synthetic results were combined to population data to derive the best estimate of the burden of prurigo nodularis in Italian adults. Results: Five articles reporting data on incidence and/or prevalence of prurigo nodularis in European populations were identified. The prevalence of prurigo nodularis ranged from 6.5 to 111.0 cases per 100,000, with a median estimate of 32.7 cases per 100,000, the incidence ranging between 2.88 and 20 per 100,000 person-years. Five other studies reported data on the severity of prurigo nodularis, measured through pruritus scores, quality-of-life indexes and/or percentage of non-response to treatment. We estimated a total of 16,280 prevalent prurigo nodularis cases in Italy, of whom 6,073 had moderate-to-severe to very severe disease. Among the latter, 1,798 estimated cases were not controlled by standard treatments. Conclusions: We retrieved and summarized recent epidemiological data on prurigo nodularis, evidencing a high burden of disease in Italy and other European countries.