A case of lichen planus caused by mercury allergy

Abstract

We report a patient with lichen planus of the buccal mucosa, the nails and the skin caused by mercury allergy. Since 1998, a 61‐year‐old man had felt stinging on his buccal mucosa when he ate or brushed his teeth and all of his nails became rough and thin in June 2000 (Fig. 1a–c). All lesions biopsied showed a dense band‐like lymphocytic infiltrate in the upper dermis and liquefaction degeneration of the basal layer (Fig. 2). Patch testing showed positive reactions to the toothpaste that he used, sodium N‐lauroyl sarcosinate 0·5% aq., mercury 0·05% pet., ammoniated mercuric chloride 1·0% pet. and thimerosal 0·1% pet. (Fig. 3). Mercury was used as a component of his dental fillings. When these were replaced by the hard resin jacket crowns, the mucosal and nail symptoms gradually improved (Fig. 1d,e).