Molluscum contagiosum

Definition:

A viral skin infection that causes raised pearl-like papules or nodules on the skin.

Causes, incidence, and risk factors:

Molluscum contagiosum is caused by a virus that is a member of the Poxvirus family. This virus is called Molluscipoxvirus Molluscum contagiosum.

This is a common infection in children. It is frequently seen on the face, neck, axilla (arm pit), arms, and hands but may occur anywhere on the body except the palms and soles. On occasion it is seen on the genitalia.

In adults, molluscum is generally seen on the genitalia as a sexually-transmitted disease. Because molluscum produces no systemic illness and is not of long-term public health or economic significance, it has not been treated as other sexually-transmitted diseases. The importance is significant in the growing population of immunocompromised people with AIDS, who may develop a fulminating (rapidly worsening) case of molluscum contagiosum.

Typically the lesion of molluscum begins as a small papule which becomes raised up to a pearly, flesh-colored nodule. The nodule often has a dimple in the center (umbilicated). These nodules may occur in lines, where the person has scratched. Scratching or other local mechanical irritation causes the virus to spread in a line or in groups (crops). The nodules are approximately 2 to 5 millimeters in diameter and painless. There is no inflammation and subsequently no redness unless the person has been digging or scratching at the lesions. In the mature molluscum, the top of the nodule may be opened with a sterile needle and a small waxy core can be seen and squeezed out of the lesion.

Molluscum contagiosum is a chronic infection and lesions may persist from a few months to a few years. These lesions ultimately disappear without scarring. Early lesions on the genitalia may be mistaken for herpes but, unlike herpes, these lesions are painless.

The virus is contagious through direct contact, as seen in children, but may spread by sexual contact. It can spread locally (autoinoculation) by shedding of the virus from lesions to adjacent normal skin areas.