Erythroplakia (or erythroplasia) is a clinical term to describe any erythematous (red) area on a mucous membrane that cannot be attributed to any other pathology. The term erythroplasia was coined by Louis Queyrat to describe a precancerous red lesion of the penis. This gave rise to the term erythoplasia of Queyrat. Depending upon the context, this term may refer specifically to carcinoma in situ of the glans penis or vulva appearing as a red patch, or may be used as a synonym of erythroplasia on other mucous membrane or transitional sites. It mainly affects the glans penis (the head of the penis), although uncommonly it may present on the mucous membranes of the larynx and rarely, the mouth or the anus.