Molluscum contagiosum pathophysiology

Molluscum contagiosum Microchapters
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Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Molluscum contagiosum from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Diagnostic criteria
History and Symptoms
Physical Examination
Laboratory Findings
X ray
Ultrasound
CT Scan
MRI
Other Imaging Studies
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2]

Overview

Molluscum contagiosum is usually transmitted via direct contact with a lesion on a human host. Following transmission, molluscum contagiosum uses the human cell machinery to replicate. On gross pathology, a central umbilication and punctiform vessels are characteristic findings of molluscum contagiosum. On electron microscopic analysis, typical brick-shaped poxvirus particles inside the infected tissue are characteristic findings of molluscum contagiosum.

Pathogenesis

• The human molluscum contagiosum virus (MCV) is a DNA poxvirus.
• MCV has no animal reservoir, infecting only humans, as did smallpox.
• Human are the only known host for MCV.
• MCV replicates in cells cytoplasm. This may be related to genetic similarity in variola and vaccinia viruses more than one-half.
• In adults, molluscum infections are often sexually transmitted and usually affect the genitals, lower abdomen, buttocks, and inner thighs. In rare cases, molluscum contagiosum infections are also found on the lips, mouth, and eyelids. It is spread through direct contact or shared articles of clothing (including towels).
• MCV can commonly cause asymptomatic cutaneous neoplasms. Children and sexually active adults as well as persistent opportunistic acquired immunodeficiency syndrome (AIDS)-associated disease are more sensitive to the virus and more in danger for cutaneous neoplasm.

Genetics

• Molluscum contagiosum virus (MCV) genome was firstly described and reported by Senkevich et al.
• MCV possesses 59 genes predicted to code for novel proteins including MHC-class I, chemokine and glutathione peroxidase homologs not found in other poxviruses. The MCV genomic data is near complete which can allow the investigation of host defense mechanisms. These information also can provide new possibilities for the development of therapeutics for treatment and prevention of the MCV infection.
• Molluscum contagiosum inhibits the host inflammatory response. This unique feature seems to be related to some of the specific genes that are present in its genome.
• Scientists have sequenced more than 190-kilobase pair genome of MCV. These genome findings have revealed that the virus potentially encodes approximately 182 proteins, 105 of which have direct counterparts in orthopoxviruses (OPV). Another study suggests that MCV lacks counterparts to 83 genes of the smallpox virus, including those important in suppression of host responses to infection, nucleotide biosynthesis, and cell proliferation.

Gross Pathology

• In a dermoscopic exam of infected tissue, a central umbilication with polylobular, white to yellow amorphous structures is visualized which is typical for diagnosis. A peripheral crown of radiating or punctiform vessels may also be seen.

Microscopic Pathology

Electron microscopic evaluation of tissue is not a part of routine diagnosis procedure, but if done it may show:

• Typical brick-shaped poxvirus particles inside the infected tissue which is highly specific for diagnosis.
• Electron microscopy can also identify infected cells that appear normal on light microscopy.