HUMAN PAPILLOMAVIRUS TYPE 60-ASSOCIATED PLANTAR WART - RIDGED WART

Background: We had recently cloned a new cutaneous human papillomavirus type 60 (HPV-60) from a plantar cyst with characteristic pathologic changes and identified it in additional cysts. However, it is not known whether or not HPV-60 infection causes the other cutaneous lesions. Observations: Six plantar warts were found in five patients. These warts were found either with concomitant plantar cysts (four patients) or without an accompanying cyst (one patient). All warts showed a similar clinical appearance, including a smooth and slightly elevated surface and the retained appearance of the dermal ridges. Their histopathologic features were identical to those found in the wall of the cysts reported previously, namely hyperkeratosis with vacuolated structure with or without nuclei in the horny layer and amorphous eosinophilic cytoplasmic inclusions in the cells with peripherally located nuclei in the granular and prickle cell layers. By Southern blot analysis, all warts were found to harbor HPV-60 DNA. In addition, immunohistochemistry and in situ hybridization analysis revealed the presence of viral capsid antigen and viral genome in these lesions, respectively. Conclusion: We conclude that HPV-60 infection on the plantar skin causes the warty lesion, designated as ridged walt, distinct from those infected with other cutaneous human papillomaviruses.