Molluscum contagiosum. A clinicopathologic study

Molluscum contagiosum: a case series

Molluscum contagiosum is a benign and contagious disease of the skin. In a series of 30 consecutive patients, 15 had full resolution, 12 were improved. Brief case histories of the 15 patients who fully resolved are presented. The homeopathic medicines most frequently associated with positive outcome were Natrum sulphuricum, Sulphur and Natrum muriaticum.

Identification and typing of molluscum contagiosum virus in clinical specimens by polymerase chain reaction

A polymerase chain reaction (PCR) which enables the detection of molluscum contagiosum virus (MCV) genomes in either fresh or formalin-fixed clinical specimens is described. The primers used were designed to amplify a 167 bp region of the 3.8 kbp HindIII fragment K of the MCV 1 genome. The ability of this PCR to detect three common MCV types (1, 1v and 2) in clinical specimens was confirmed using frozen extracts from 75 molluscum lesions, and digests of single sections of 11 formalin-fixed, paraffin-embedded lesions; all of which had been previously typed by Southern hybridisation. In addition, 2 specimens previously negative by hybridisation were shown to be positive for MCV DNA by PCR. Confirmation of the identity of the PCR products and distinction between the two major MCV types (MCV 1/1v versus MCV 2) was achieved by comparison of the results of cleavage with the restriction endonucleases Hhal and Sacl. Sequencing of the PCR products revealed complete homology between MCV 1 and 1v, but minor nucleotide variations between MCV 1/1v and MCV 2 were identified. As well as providing a highly sensitive means of diagnosis, the technique may also prove useful for investigations into the pathogenesis, epidemiology and natural history of molluscum contagiosum infection.

Proinflammatory properties of molluscum bodies

Molluscum contagiosum, a condition characterized by benign viral tumours, occasionally becomes inflamed and regresses spontaneously, an event probably initiated by a host cell-mediated immune rejection against the lesion, but it inevitably involves the disruption of the epidermal tissue to expose the molluscum bodies to the tissue fluids of the dermis. It has been suggested that the molluscum bodies induce inflammation by a mechanism similar to that involved in ruptured epidermal cysts or in acne. Despite the occasional development of inflammation in molluscum contagiosum, the proinflammatory properties of molluscum bodies have never been studied in vitro. Thus, in the present study we sought to determine whether molluscum bodies exert a proinflammatory effect by inducing neutrophil chemotaxis. When exposed to fresh serum in vitro, water-insoluble components of molluscum bodies activated the alternative complement pathway to produce chemotactic C5a/C5a des Arg. We also found that an aqueous extract of molluscum bodies exerted potent chemotactic activity for neutrophils. Remarkably high amounts of the immunoreactive proinflammatory cytokines IL-8 and GRO alpha were present in the extract even when compared with psoriatic scale extracts. Gel filtration HPLC of the extract demonstrated the presence of neutrophil chemotactic activity over a wide range of molecular mass. These data suggest that disruption of the epidermal wall of molluscum bodies induces acute inflammatory changes by activation of the alternative complement pathway on exposure to the tissue fluids, and that the molluscum bodies themselves release proinflammatory cytokines and other neutrophil chemotactic factors on decomposition.

Molluscum contagiosum-induced comedo and secondary abscess formation

A 9-year-old boy had recurrent formation of fluctuating abscesses of the forearms, leading to surgical incisions. Histopathologic examinations revealed that the etiologic agent was a molluscum virus in the lower portion of a pilosebaceous follicle, which formed a comedo. The comedones developed into pustular and cystic lesions after the boy attempted to squeeze out the contents. Two different reaction patterns to molluscum contagiosum seem to be present: a lymphocyte-mediated immunologic reaction in normally regressing lesions, and an acute inflammatory reaction due to disruption of infected epidermal tissue into the dermis, as seen in this patient.

Demonstration of a unique viral structure: the molluscum viral colony sac

Using scanning electron microscopy to study molluscum contagiosum lesions, it has been possible to demonstrate a unique, well defined sac enclosing the virion colony of each infected keratinocyte. This confirms the presence of a structure demonstrated over 50 years ago by micro-dissection, but ignored since it is not seen on either light or transmission electron microscopy. It is postulated that this sac, of unknown origin, favours replication of the virions by providing a site that is both anatomically and immunologically privileged. Such relatively unimpeded growth of the virions results in an enlarged cell in which the cytoplasm and nucleus are compressed into a thin outer shell. In the aggregate, this produces a tumour of virus-packed cells rather than a tumour composed of virus-induced cell hyperplasia.

The identification of molluscum infection by immunohistochemical means

Tissue obtained from formalin-fixed, paraffin-embedded blocks containing molluscum contagiosum virus was used as a source of antigen to generate a polyclonal antibody against molluscum contagiosum virus. This antibody recognized an antigen in molluscum bodies which was preserved during routine fixation and embedding. The antibody can be used with standard immunohistochemical methods to identify molluscum contagiosuminfection in inflamed and distorted tissue specimens. Our data indicate that paraffin-embedded, formalin-fixed material can be used as an antigenic source to generate antibodies with diagnostic potential.