Dear Editors, oral lichen planus (OLP) is an autoimmune-mediated inflammatory disease of the oral cavity with an estimated global prevalence of about 1.0 % [1]. Mildly affected individuals may only display the characteristic clinical features, that is, Wickham's striae of the oral mucosa, but are otherwise asymptomatic. However, certain patients may suffer from moderate to severe pain that interferes with food intake and dental hygiene [2]. Furthermore, patients with OLP are more likely to develop oral squamous cell carcinoma with a recently reported malignant transformation rate of 2.3 % [3]. Apremilast, a well-tolerated phosphodiesterase-4-inhibitor, was shown to be effective in some difficult-to-treat OLP cases (six patients in total) [4][5][6][7].In this retrospective, multicenter cohort study, performed in three European tertiary referral hospitals (
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