Various changes may occur in the gingiva and/or the periodontium as an expression of existing infection with human immunodeficiency virus. Thus, periodontal disease, characterized by unusual course, progress, and resistance to treatment, may occur with increased frequency. Clinically, pseudomembranous or erythematous (atrophic) forms of candidiasis or so-called papillary hyperplasia may be caused by ubiquitous fungi. Although Candida albicans infections arise frequently on the cheek, the palate, the dorsum of the tongue, and the corner of the mouth (angular cheilitis), gingivo-periodontal manifestation is more unusual. Because of the existing immune defect, infection with or reactivation of various viruses may occur. Recurrent, progressive destructive ulcerations may be caused by herpes simplex virus 1 or 2, but apparently limited ulcerations may be an expression of a disseminated cytomegalovirus infection. Oral Kaposi's sarcoma appears initially as bluish or reddish spots; these may transform during the course of the disease into blue, occasionally lymphoma-like or lymphangioma-like, exophytic tumors.