Molluscum Contagiousum
This image shows multiple lesions, with some which have resolved in the centre of the picture. The lesion at the top left shows typical umbilication. The multiple lesions highlight the highly infectious nature of the molluscum contagiousum virus.
Features
Molluscum contagiousum are shiny, pearly white, umbilicated papules. The lesion starts very small and becomes identifiable with a magnifying glass at roughly 1mm in diameter. The lesion continues to grow, albeit slowly, and may reach 5-10mm by 6-12 weeks. The lesions are often multiple due to the virus being disseminated from the original lesion. Most cases regress spontaneously within 6-9 months, although some may persist for several years. Lesions may become inflamed, secondarily infected or eczematized.
The lesions may present anywhere on the skin, but are commonly found on the neck, trunk and axillae. Due to the infective nature of the lesions, sexual contact may result in transmission of the causative virus. In these cases, lesions are commonly found in the anogenital region.
Refractory mollusca is associated with decreased host immunity (such as in AIDS). This results in a different pattern of lesions, involving the face in particular.
Incidence
The disease is common, but its incidence in most areas of the world is unknown. It is principally an infection of childhood, although infection is rare under the age of 1 year. Peak age of incidence is 10-12. Boys are more commonly affected than girls, perhaps due to an increased use of swimming pools and participation in contact sports.
Aetiology
Molluscum contagiousum is caused by infection with a Pox virus, known as the molluscum contagiousum virus (MCV). There are two genomes (MCV-1 and MCV-2), with MCV-1 causing by far the majority of infections. The lesions are highly infectious.
Differential Diagnosis
Pyogenic granuloma. Keratoacanthoma. Epithelioma.
Treatment
Patients should be advised to use seperate towels from others, not share any clothing which may have come into contact with the lesions and avoid close contact with others.
Mollusca will resolve spontaneously given enough time, but there are several treatments available. Lesions may be "spiked" with liquid nitrogen, phenol or iodine. They often require repeated treatments and can be painful. Topical Cidofovir has also been shown to cause resolution of the lesions. If large enough, curettage and diathermy may be appropriate.
