MOLLUSCUM CONTAGIOSUM

The pox viruses include a large number of related DNA viruses that infect various vertebrate hosts. The pox viruses are responsible for infections in humans, along with the main manifestations of these infections. Systemic human disease can result from infection with smallpox (variola major) virus, a poxvirus that infects only humans or from zoonotic infection with monkey pox virus. Other poxvirus infections cause primarily localized skin disease in humans. Molluscum contagiosum virus (MCV) is an obligate human pathogen that causes distinctive proliferative skin lesions; Molluscum contagiosum is the most frequent human disease resulting from poxvirus infection. Exposure to animals infected with other poxviruses can also cause localized skin disease in humans.

Molluscum contagiosum is generally a benign disease consisting of pearly, flesh colored, and umbilicated skin lesions 2 to 5 mm in diameter with a characteristic dimple at the center. A relative lack of inflammation and necrosis distinguishes these proliferative lesions from other poxvirus lesions. The lesions occur singly or in clusters. MCV is a human poxvirus that is transmitted by close contact, including sexual intercourse. Swimming pools are a common vector for transmission. Atopy and compromise of skin integrity increase the risk of infection. Lesions may be found anywhere on the body except the palms and soles and may be associated with an eczematous rash. The incubation period ranges from 2 weeks to 6 months, with an average of 2 to 7 weeks. In most cases, the disease is self-limited and regresses spontaneously after 3 to 4 months in immunocompetent hosts. There are no systemic complications, but skin lesions may persist for 3 to 5 years. Molluscum contagiosum develops especially often in association with the advanced stages of HIV infection, with a prevalence of 5 to 18% among HIV-infected patients. The disease is often more generalized, severe, and persistent in AIDS patients than in other groups, frequently involving the face and upper body. Extensive Molluscum contagiosum has also been reported in conjunction with other types of immunodeficiency.

The diagnosis of Molluscum contagiosum is typically made by its clinical presentation and can be confirmed by histologic demonstration of the cytoplasmic eosinophilic inclusions, or Molluscum bodies, that are characteristic of poxvirus replication. MCV cannot be propagated in vitro, but electron microscopy and molecular studies can be used for its identification. There is no specific systemic treatment for Molluscum contagiosum, but a variety of techniques for physical ablation have been used. Molluscum contagiosum may respond to effective control of HIV infection with highly active antiretroviral therapy. Cidofovir displays in vitro activity against many poxviruses, including smallpox virus and MCV, and case reports suggest that parenteral or topical Cidofovir may have some efficacy in the treatment of recalcitrant Molluscum Contagiosum in immunosuppressed hosts.