of immunodeficiency, almost always human immunodeficiency virus (HIV) infection. This condition is not considered to be a true idiopathic leukoplakia since the causative agent has been identified. It is one of the most common oral lesions associated with HIV infection, along with pseudomembraneous candidiasis. The appearance of the lesion often heralds the transition from HIV to acquired immunodeficiency syndrome (AIDS). Syphilitic leukoplakia This term refers to a white lesion associated with syphilis, specifically in the tertiary stage of the infection. It is not considered to be a type of idiopathic leukoplakia, since the causative agent Treponema pallidum is known. It is now rare, but when syphilis was more common, this white patch usually appeared on the top surface of the tongue and carried a high risk of cancerous changes. It is unclear if this lesion was related to the condition itself or whether it was caused by the treatments for syphilis at the time. Esophagus Leukoplakia of the esophagus is rare compared to oral leukoplakia. The relationship with esophageal cancer is unclear because the incidence of esophageal leukoplakia is so low. It usually appears as a small, nearly opaque white lesion that may resemble early esophageal squamous cell carcinoma. The histologic appearance is similar to oral leukoplakia, with hyperkeratosis and possible dysplasia. Bladder In the context of lesions of the mucous membrane lining of the bladder, leukoplakia is a historic term for a visualized white patch which histologically represents keratinization in an area of squamous metaplasia. The symptoms may include frequency, suprapubic pain (pain felt above the pubis), hematuria (blood in the urine), dysuria (difficult urination or pain during urination), urgency, and urge incontinence. The white lesion may be seen during cystoscopy, where it appears as a whitish-gray or yellow lesion, on a background of inflamed urothelium and there may be floating debris in the bladder. Leukoplakia of the bladder may undergo cancerous changes, so biopsy and long term follow up are usually indicated. Anal canal Leukoplakia of the anal canal is rare. It may extend up to the anorectal junction. On digital examination it feels hard and granular, and at proctoscopy, it appears as white plaques which may be diffuse, circumferential, or circumscribed. The histologic appearance is similar to oral leukoplakia, with hyperkeratosis and acanthosis. It may be asymptomatic, with symptoms due to other lesions such as hemorrhoids or fissures. Progression to anal stenosis has been described. The malignant