Leukoplakia causes thick, raised, plaque-like white patches on the mucous membranes of the mouth. Patches may also appear transparent or gray and usually have at least one area with a clear margin. Cracking may also occur. Although they can be bothersome depending on the type, leukoplakia patches are often painless. Commonly affected regions include: inner lining of the cheeks; gums; bottom of the mouth under the tongue; tongue. In some cases, C of the body aside from the mouth. Of these areas, the genitals are most frequently affected.