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Frictional keratosis is an epithelial response to mild chronic trauma such as chronic superficial chewing (tongue, buccal mucosa and lips); it is also known as "morsicatio linguarum," "morsicatio buccarum," or "morsicatio labiorum." Other possible causes of frictional keratosis are a sharp tooth, an ill-fitting denture or contact with certain material including cough drops, sunflower seeds, or, as in this case, Nicorette gum. It is difficult to determine whether the direct contact with Nicorette gum or the chemicals comprising Nicorette are causing the white lesions. The histology (Figures 5-6) supports direct frictional keratosis while the history of the white lesions not regressing after six months of not holding the Nicorette gum on the left side (Figures 1-3) tells another story. It is too early to presume that Nicorette gum contains any chemicals that can cause the white patches and for that reason, we choose to call it frictional keratosis based on the histology.
Frictional keratosis can affect patients of any age with no gender predilection. It is commonly found in younger patients involving the lips, cheeks, and lateral tongue. On palpation, it ranges from smooth to rough, irregular and leathery in consistency. Histologically, it is made up of hyperkeratosis, usually with superficial bacterial colonization. The spinous layer is usually hyperplastic and the connective tissue may or may not be inflamed or fibrotic. The treatment of choice is removal of the irritating factor. It is best to biopsy if the lesion persists. It is also important to keep the patient on regular follow-up visits and re-biopsy if the lesion changes to red, ulcerates, or grows larger.
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