Linear lichen planus in the region of the mandibular nerve caused by an allergy to palladium in dental metals.

We observed a case of linear lichen planus extending from the right cheek to the jaw, which was accompanied by itching and an unusual sensation in the mouth. The eruption was located along the mandible and aligned with the mandibular nerve. The right molars of the patient contained metal compounds and these were considered to be the cause of his disease. Patch testing with various dental metals showed positive reactions to palladium and platinum. A biopsy specimen showed a lichenoid reaction in the lesional tissue, and dermal contact dermatitis was noted at the palladium patch test site. His dentist reported that palladium-silver-gold or nickel-chrome alloys without platinum had been used in the crown and bridge of his molars. After removal of the dental alloys, the skin eruption resolved with some residual hyperpigmentation. In addition, the peculiar mouth sensation disappeared dramatically within 2 months.