Aminolevulinic acid (ALA)-assisted photodynamic diagnosis of subclinical and latent HPV infection of external genital region.

The relatively high recurrence rate of genital warts can be attributed to the unsuccessful elimination of viruses in areas of subclinical and latent infection. Therefore, the identification and treatment of the subclinical and latent infection is a key to reduce the recurrence. The goal of this study is to investigate the usefulness of 5-aminolevulinic acid (ALA)-assisted in situ fluorescence diagnosis of subclinical lesion and latent HPV infection. A total of 30 patients with histologically confirmed genital warts (condylomata acuminata) were subjected to topical application of ALA, acetic acid test, histopathologic examination and HPV DNA subtyping. Topical application of ALA was performed by applying 20% ALA cream to the lesion plus 2-cm margin for 2h followed by fluorescence examination. Correlations between histopathologic examination, aceto-whitening test, HPV DNA subtyping and fluorescence were examined. All warty lesions and subclinical lesions (n=25) showed red fluorescence and harbored HPV DNA (HPV6 or 11). Latent HPV infections at 0.5-2 cm away from the warty lesion also showed red fluorescence. Nonspecific fluorescence was associated with mucosa, inflammatory infiltration and erosive lesion. ALA-assisted photodynamic diagnosis could be employed for the detection of the lesion and subclinical lesion of genital warts. It is also useful in detecting latent HPV infection.