Nationwide epidemiological and clinical survey of juvenile‐onset morphea in Japan

Juvenile-onset morphea can severely impact activities of daily living by causing functional disability. This study was performed to clarify the epidemiological and clinical characteristics of juvenile-onset morphea in Japan. We conducted a nationwide, two-part postal survey. The first survey aimed to estimate the number of patients with juvenile-onset morphea, while the second survey aimed to elucidate the epidemiological and clinical characteristics of juvenile-onset morphea. This study included patients of all ages with juvenile-onset morphea whose age at disease onset was <18 years and who visited a medical institution from 1 January, 2016 to 31 December, 2020. The first survey identified 371 patients with juvenile-onset morphea. The second survey collected detailed clinical information for 315 patients with juvenile-onset morphea. We estimated that the number of patients diagnosed with juvenile-onset morphea from 2016 to 2020 was 591 (95% confidence interval 479-702) among children aged <18 years. The estimated annual incidence rate of juvenile-onset morphea ranged from 2.11 to 2.87 per 1 000 000 children aged <18 years from 2016 to 2019. The mean age at onset was 7.7 years. Regarding subtypes, linear morphea was the most common, followed by circumscribed morphea. Complications and treatments varied widely by subtype, with local treatment primarily used for circumscribed morphea. By contrast, patients with linear morphea, generalized morphea, pansclerotic morphea, and mixed morphea had severe complications affecting daily life, and they received systemic immunosuppressive therapy more frequently. The prognosis of juvenile-onset morphea was generally favorable. The results of this study are expected to help in the development of appropriate diagnostic and therapeutic approaches for juvenile-onset morphea.