Oral hairy leukoplakia: pathogenetic aspects and significance of the lesion

Oral hairy leukoplakia in HIV-seropositive persons is considered as a highly serious sign and places the patient in the AIDS-related complex group according to the classification recommended by the Centers for Disease Control. Epstein-Barr virus (EBV) is thought to be the cause. Based on the investigation of 14 of our own cases and a review of the literature, we conclude that so called hairy leukoplakia does not have a specific histopathologic pattern. Identical lesions can be caused by fungus infection, or biting and other kinds of mechanical irritation. Both fungal infection and EBV infection have been proven in a high percentage of the lesions. However, EBV has been found also in apparently normal oral mucosa. This questions the assumption that the virus is the cause of the lesions. In our investigation the presence of "hairy leukoplakia" did not reflect the clinical status of the patient. The best indicator of the clinical status was the T-lymphocyte subset CD4+ number in the peripheral blood. It appears that low CD4+ counts, candidiasis and the presence of replicating EBV in the epithelial cells are parallel markers of increasing immunodeficiency.