Wednesday 15 June 2011
UI953: - Molluscum contagiosum
A lesion consists of several inverted lobules of hyperplastic squamous epithelium which expand into the underlying dermis.
The lobules are separated by fine septa of compressed dermis.
Eosinophilic inclusion bodies form in the cytoplasm of keratinocytes just above the basal layer, and progressively enlarge.
At the level of the granular layer, the bodies become increasingly hematoxyphile and occupy the entire cell.
These molluscum bodies are eventually extruded with keratinous debris into dilated ostia, which lead to the surface.
Areas of hair bulb differentiation, or epithelial proliferation mimicking a basal cell carcinoma, may occur at the margins of a lesion.
Molluscum contagiosum has been reported in epidermal cysts, but some of these cases may simply represent pilar infundibula dilated by cornified cells and molluscum bodies.
A variable chronic inflammatory cell infiltrate is seen in regressing lesions, and is thought to represent a cell-mediated immune reaction.
However, in the early eruptive phase there is no inflammatory response.
Inflammation and a foreign-body reaction may also be related to extrusion of molluscum bodies into the dermis.
Rarely, an atypical lymphocytic infiltrate (‘pseudoleukemia cutis’, ‘pseudolymphoma’) may be found.
In one case, the atypical cells were CD8+ T lymphocytes with scattered CD30+ cells.
In another they were CD4+, with some CD30+ cells.
Another rare inflammatory response is a moderate to heavy infiltrate of eosinophils, with the formation of flame figures.
Secondary infection and ulceration may occur.
Molluscum folliculitis is an uncommon pattern seen mainly in immunocompromised persons.
It has also followed leg shaving.
The molluscum bodies are present within the follicular epithelium.
Molluscum contagiosum has also been reported in association with a nevocellular nevus, a halo nevus, with the Meyerson phenomenon, with cutaneous lupus erythematosus and with human papillomavirus (HPV).
Co-infection with cryptococcosis has been reported in a patient with HIV infection.
In one patient with systemic lupus erythematosus, metaplastic bone was present in the dermis adjacent to each lesion of molluscum contagiosum.
cutaneous viral diseases