A 44-year-old man with a history of gastroesophageal reflux disease and anxiety presents for evaluation of mouth ulcers recurring for the past 2 years. The painful ulcers resolve within 2 weeks but recur on different mucosal surfaces. He denies new medications, foods, or oral hygiene products and involvement of cutaneous or other mucosal surfaces. He is uncertain whether he has a family history of oral ulcers. He was previously prescribed anesthetic rinses and fluconazole, without benefit. His current medications include omeprazole and lorazepam. Intraoral examination demonstrates an ulcer with a pseudomembrane and erythematous halo on the left lateral surface of the tongue (Figure). Physical examination results are otherwise normal.