What is the pathogenesis and disease progression of molluscum contagiosum infection?

Updated: Aug 09, 2018
  • Author: Ashish C Bhatia, MD, FAAD, FACMS; Chief Editor: Dirk M Elston, MD  more...
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Answer

The molluscum contagiosum virus replicates in the cytoplasm of epithelial cells, producing cytoplasmic inclusions and enlargement of infected cells. This virus infects only the epidermis. Infection follows contact with infected persons or contaminated objects, but the extent of necessary epidermal injury is unknown. The initial infection seems to occur in the basal layer, and the incubation period is usually 2-7 weeks. This is suggested by the fact that, although viral particles are noted in the basal layer, viral deoxyribonucleic acid (DNA) replication and the formation of new viral particles do not occur until the spindle and granular layers of the epidermis are involved. Infection may be accompanied by a latent period of as long as 6 months.

Following infection, cellular proliferation produces lobulated epidermal growths that compress epidermal papillae, while fibrous septa between the lobules produce pear-shaped clumps with the apex upwards. The basal layer remains intact.

Cells at the core of the lesion show the greatest distortion and are ultimately destroyed, resulting in large hyaline bodies (ie, molluscum bodies, Henderson-Paterson bodies) containing cytoplasmic masses of virus material. These bodies are present in large numbers and appear as a white depression at the center of fully developed lesions. Occasionally, the lesions can progress beyond local cellular proliferation and become inflamed with attendant edema, increased vascularity, and infiltration by neutrophils, lymphocytes, and monocytes. Viral-derived proteins inhibit mitochondrial-mediated apoptosis. [7]

As with other poxviruses, molluscum contagiosum virus does not appear to develop latency but evades the immune system through the production of virus-specific proteins. Cell-mediated immunity is most important in modulating and controlling the infection. Children and patients with HIV infection generally have more widespread lesions. Prevalence of molluscum contagiosum virus in patients with HIV may be as high as 5-18%, and the severity of infection is inversely related to the CD4 T-lymphocyte count. More extensive and resistant infections also are noted in patients receiving prednisone and methotrexate.

The virus is not strongly immunogenic, as it infrequently induces antibody formation. Specific antibodies have been found in approximately 80% of patients and in about 15% of control subjects. A role for humoral immunity in regression of lesions is not established. Reinfection is common.


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