CD14 Mouth ulcer mayhem secondary to dental fillings

Abstract Dental amalgam contains mercury, which may cause an uncommon lichenoid allergic contact dermatitis (ACD) affecting the oral mucosa in direct contact with the amalgam filling. Distinguishing a lichenoid amalgam reaction from oral lichen planus is challenging, both clinically and histopathologically. This case illustrates the important role that patch testing to dental materials can play in providing a simple answer in the management of resistant cases of mouth ulceration, protecting patients from exposure to potentially toxic immunosuppressive treatments. A 64-year-old woman presented with a 5-year history of oral ulceration affecting the buccal mucosa and tongue bilaterally. These ulcers were persistent, very painful and bled intermittently, causing a significant adverse effect on her quality of life. She worked as a manager at a local wildlife sanctuary, and hobbies included walking, writing and artwork. An incisional biopsy taken from an ulcer in the left buccal mucosa demonstrated a dense lichenoid inflammatory cell infiltrate. The oral surgical team treated her for presumed ulcerative oral lichen planus with multiple treatments, including topical steroids, high doses of oral prednisolone, hydroxychloroquine, mycophenolate mofetil and azathioprine. She gained only very minimal benefit. The oral surgeons then requested dermatological advice for the next potential treatment option, which was suggested to be rituximab. At this point, the surgeons noticed that the ulcers seemed to be most prominent at sites of the patient’s longstanding amalgam fillings and she was referred for patch testing. Patch tests were performed to the British Standard series, medicaments series and oral and dental series. Positive reactions were noted to both amalgam (D2+/D4+) and mercury (D2+/D4+). The patient had her amalgam fillings replaced with white acrylate fillings, and her oral ulceration completely healed without the need for any further immunosuppression. Clinically and histologically, lichenoid ACD secondary to dental fillings can be indistinguishable from idiopathic oral erosive lichen planus. However, the proximity of ulceration to dental filling materials should always raise the possibility of a lichenoid ACD and trigger referral for patch testing, preferably prior to systemic medications being tried. This case highlights the importance of patch testing in patients with localized, asymmetrical, difficult-to-treat oral ulcers adjacent to amalgam fillings, which could spare the patient from exposure to potentially harmful immunosuppressive treatments.