The mouth and genitals
Mucous membranes are covered with a modified stratified squamous epithelium that lacks a stratum corneum. This makes them moist and susceptible to infection, and to conditions not seen elsewhere. In contrast, the skin around them is like that on other body sites, and develops the standard range of skin disorders. It follows that the diagnosis of puzzling mouth or genital changes is often made easier by look-ing for skin disease elsewhere.
The mouth can harbour an enormous range of dis-eases, affecting each of its component structures. Inflammatory and infectious disorders of the mouth are usually either red or whitealeading to the terms erythroplakia and leukoplakia, respectively. These are descriptive terms but not diagnoses. A biopsy will help sort out the non-dysplastic causes, such as lichen planus and candida infections, from the dysplastic ones that are the precursors of carcinoma.
Some skin diseases cause ulceration in the mouth. These ulcers are accompanied by skin diseases else-where on the body, and making a diagnosis there is easier than in the mouth. In other patients with mouth ulcers, the course of the ulcers or erosions, and their size and location in the mouth, provide diagnostic clues. Table 13.4 lists some common tongue troubles.