A condition that may affect the lining of the mouth and tongue. It is an inflammatory condition that causes soreness, sensitivity and discomfort. The condition has a variety of appearances. It is commonly seen as a network of fine white lines on the inside of the cheeks, often on a reddish background. Less commonly it can appear as white patches of different sizes and shapes on the tongue or roof of the mouth. Occasionally the gums can be affected, both with white patches and, sometimes, shiny red sore-looking gums.