It is a Pox virus infection of the skin and mucous membrane caused by virus in the subgenus Molluscipox virus. It is a large brick shaped DNA pox virus measuring 300-240 nm.
History – Bateman first described and named it in the 19th centuary. In 1841, Henderson and Paterson describes intracytoplasmic inclusion bodies now known as Molluscum bodies or Henderson – Paterson bodies
Clinical presentation
Multiple or solitary dome shaped, umbilicated, waxy papules which range in size from 2 to 8 mm in diamtre
Age – common in children but can occur in all the age group
Sites – predilection for head and neck, trunk, flexural areas or the genitalia of children and adolescents. rarely seen on the palms and soles, tattoos, herpes zoster scar, burned skin.
Modes of transmission –
Direct body contact
Through minor abrasions
Indirectly via fomites
sexually transmitted
use of swimming pools
In patients on Tacrolimus or methotrexate
Incubation period – 14 to 50 days
Spontaneous regression occurs in immunocompetent persons. Regression is primarily by cell mediated immune response or by the Ubiquitin – proteosome system
Microscopy –
Epidermis is acanthotic
Lesion consists of several inverted lobules of hyperplastic squamous epithelium which expand into underlying dermis. Lobules are separated by fine septa of compressed dermis
Epidermal cells contain large intracytoplasmic inclusion bodies called molluscum bodies
Inclusion bodies in keratinocytes appear just above the basal layer and progressively enlarge
These bodies first appear as minute intracytoplasmic ovoid eosinophilic structure in the lower cells of stratum malpighii at 1 or 2 layers above basal cell layer
Molluscum bodies increase in size as the infected cell moves towards surface.
At the level of granular layer, the bodies become increasingly haematoxyphilic (basophilic) and occupy the entire cell. They displace and compress the nucleus so that it appears as thin crescent at the periphery
In horny layer Molluscum bodies are basophilic measuring 35Aμm in diametre lie enmeshed in a network of eosinophilic horny fibres
In the centre of the lesion, stratum corneum disintegrates. Molluscum bodies are extruded along with keratinous debris into dilated ostia which leads to surface
Thus a central crater is formed.
Secondary infection and ulceration may occur. In some cases eosinophilic infiltrate is present
In early eruptive phase inflammation is absent but later inflammation and foreign body giant cell reaction occurs due to extrusion of molluscum bodies into dermis. Eosinophilic infiltrate can also be present
Electron microscopy – Reveals the molluscum bodies which contains large number of virions embedded in protein matrix
Diagnosis of Molluscum contagiosum can be done in clinic by using10% kOH. 10% KOH is added to crushed material of the core of MC. after few minutes keratin is sufficiently cleared . Only clustered, round or oval shaped Molluscum bodies are easily seen in the specimen
Treatment-
No treatment is required as involution occurs in immunocompetent persons
Physical modalities – Cryotherapy, or curettage or manual extraction
Topical and intralesional therapy – Cidofovir, Cantharidin, Imiquimod
References
Xiaowei Xu, Lori A. Erickson, David E Elder. Diseases caused by viruses.In: Elder, David E, Elenitsas, Rosakie, Johnson, Bernette L, Murphy George F. Levers Histopathology of the skin, 9th edition. 2005