Current Status of Prurigo Nodularis in Japan: A Retrospective Study Using a Health Insurance Claims Database

Background/Objectives: Prurigo nodularis (PN) is associated with considerable disease burden. Limited information exists about the epidemiology, treatment patterns, and impact of PN. This retrospective study used Japanese health insurance claims data to investigate the prevalence and incidence of PN from 2006 to 2021. Methods: A cross-sectional study design was used to estimate prevalence and incidence longitudinally; a cohort design was used to assess comorbidities, treatment patterns, and healthcare resource utilization (HCRU). Results: Over the study period, data from 297,545 to 10,081,414 individuals were available annually; in 2020, 1946 individuals were diagnosed with PN. The prevalence and incidence of PN showed little variation over the study period; in 2021, the prevalence was 41 per 100,000 persons. Although there was a tendency for a higher prevalence of PN in childhood, the prevalence and incidence were similar in other age groups and were slightly higher in females. Inflammatory skin diseases and atopic diathesis were common comorbidities. The most prescribed treatments for adults with PN were topical steroids (78%), oral antihistamines (68%), and moisturizers (54%). Oral steroids, macrolides, and psychotropics were prescribed to >10% of patients. Individuals with PN who also had atopic dermatitis (AD) received higher cumulative doses of stronger potency topical steroids, local steroid injections, and oral steroids than those without concomitant AD. Additionally, HCRU was higher in individuals with AD. Conclusions: Although patients are usually treated according to the guidelines, there is an unmet need for more effective treatments for PN due to the frequent use of intensive and late-line treatments.