Characteristics, comorbidities, and treatment practices of lichen planus in Northern Finland: A register-based study among 619 subjects.

Background and Aims: Lichen planus (LP) is a common itching skin disease where lesions appear on the skin and mucous membranes. However, the epidemiology of LP is not yet sufficiently understood. The aim of this study was to retrospectively map out the characteristics, comorbidities and treatments of patients diagnosed with LP. Methods: This is a retrospective hospital patient registry-based study performed between 2009 and 2021 in a secondary care hospital (Oulu University Hospital) in Northern Finland. All patients with recorded diagnosis of LP were included in the study. Characteristics, comorbidities, and treatments of LP patients were studied. Results: In total, 619 patients were verified from the hospital health records. The mean age of patients was 54.2 years and the majority were female (58.3%). Most of the patients had symptoms in more than two skin areas (mean 2.7 skin areas), lower limbs being the most common site (74.0%). A third of patients (34.7%) had oral LP lesions. Nearly fifth (19.4%) of the subjects had a history of previous LP. Of comorbidities found among LP subjects, obesity (22.5%), malignancies (19.4%), depression (12.8%), and thyroiditis (12.4%) were seen more often than in general Finnish population. The most used form of treatment was topical corticosteroids (97.6%), followed by phototherapy 26.8%. Systemic treatments such as prednisolone and methotrexate had been used in 7.6% and 1.1% of the patients, respectively. Conclusion: LP patients had a heightened risk for several comorbidities, which should be considered when managing patients with LP.