LAUSR

We report on a 59-year-old lady with a nine-month history of biopsy-proven, severe erosive oral lichen planus (OLP) that was refractory to multiple treatments, who experienced significant clinical improvement after three doses of the anti-interleukin-23 (IL-23) monoclonal antibody tildrakizumab. The patient had a history of wellcontrolled type 2 diabetes mellitus. She was not on any oral hypoglycaemic agents or antihypertensive medications. Examination of the oral cavity revealed active disease with reticular striations and severe erosions of the gums, palate and buccal mucosa (Fig. 1). The lesions were bilateral and symmetric. Clinically, the lesions were consistent with the modified World Health Organization (WHO) criteria and the American Academy of Oral and Maxillofacial Pathology criteria for the diagnosis of lichen planus. There was no evidence of lichen planus on examination of the skin, genitals, scalp or nails. Histology of an active lesion in the buccal mucosa revealed acanthosis and a band of lichenoid inflammation, with linear basement membrane staining for fibrinogen evident on immunofluorescence. At first presentation, treatment was commenced with isotretinoin 20mg weekly, ciclosporin 50mg twice daily, topical nystatin and topical clobetasol dipropionate 0.05% in an orabase vehicle. After 6 weeks, there was minimal improvement and the dose of isotretinoin was increased to 5mg daily and ciclosporin to 100 mg twice daily. Two months later, with no further symptomatic improvement, she had ongoing active disease with erosions of the gums, palate and buccal mucosa. She was unable to tolerate whole food and pureed all food to enable her to swallow. Screening investigations, including viral hepatitis serology and QuantiFERON-TB Gold, were negative. Tildrakizumab 100mg was injected subcutaneously at week 0 and week 4. The patient was reviewed at week 16 and at this point had experienced some symptomatic improvement. Isotretinoin and ciclosporin were ceased, and the third dose of tildrakizumab was administered. The patient was reviewed again at week 28, and her OLP had significantly improved. She was able to eat whole food again and could tolerate everything apart from very spicy curry. Examination revealed complete healing of her erosions, with residual fine reticular striations (Fig. 2). There were