Crystalline inclusions in epithelial cells of hairy leukoplakia: a new ultrastructural finding.

Hairy leukoplakia is often the first manifestation of an HIV infection. In the present study we have investigated the ultrastructural features of hairy leukoplakia in two HIV seropositive male homosexual patients. Ultrastructurally EBV particles were found in the upper prickle and keratinized epithelial cells, whereas papilloma virus particles were not found. Candida albicans were also seen in the keratinized layer. In addition two types of inclusions which have not previously been reported in hairy leukoplakia were commonly seen in the epithelial cells containing the EBV. The first was a crystalline microtubular structure which may take the form of several arrays. The second was an elongated multivesicular structure consisting of membrane-bound rounded vesicles embedded in a background of fine filaments. The vesicles were similar to the empty looking EBV particles and their mean diameter was 100 nm. Further investigations are needed to elucidate the exact nature of these structures and their relationship to the Epstein-Barr virus.