A sexually active 17-year-old man presents to the local free clinic to check some small papules that appeared on his penis. The papules are small, white lesions with a central depression. There is no discharge or pain on urination. What is the virus most likely causing these lesions?

The disease described in the vignette is molluscum contagiosum, caused by Molluscipox virus (d), a member of the Poxviridae. This self-li mi ting disease is more common in children than adults and is spread by direct contact (including sexual activity) and fomites such as towels. Biopsy of the lesions differentiates them from condyloma accuminatum caused by HPV types 6 and 11 (c). Molluscum bodies, similar to Guarnieri bodies observed with other poxviruses, are present in molluscum contagiosum and koilocytes are seen in HPV infections. Coxsackievirus A(b) can cause skin lesions, but these are vesicular; while the lesions caused by orf virus (e) are pustular in nature. Adenovirus (a) does not cause skin lesions.