Molluscum contagiosum pathophysiology
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Molluscum contagiosum Microchapters |
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Diagnosis |
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Treatment |
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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 route to the human host. Following transmission, the molluscum contagiosum uses the human body cells to replicate. On gross pathology, a central umbilication, and punctiform vessels are characteristic findings of molluscum contagiosum. On electronic microscopic analysis, typical brick-shaped poxvirus particles inside the infected tissue are characteristic findings of molluscum contagiosum.
Pathogenesis
- The infecting human molluscum contagiosum virus is a DNA poxvirus called the molluscum contagiosum virus (MCV).
- MCV is a member of the poxvirus family.
- MCV can cause a chronic localized skin infection. The skin presentations are small papules that can be compared to smallpox which is an acute, sometimes fatal, disease.
- MCV has no animal reservoir, infecting only humans, as did smallpox.
- MCV is transmitted by humans, which make the humans as only known host for MCV.
- 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. [1]
- MCV replicates in cells cytoplasm. This may be related to the similarity of its genes more than one-half to those found in variola and vaccinia viruses.
- In adults, molluscum infections are often sexually transmitted and usualy 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).
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.[2]
- Although molluscum contagiosum replicates in cells cytoplasm, which may be related to the similarity of its genes more than one-half to those found in variola and vaccinia viruses, still many genes found in variola and vaccinia are not present in the molluscum contagiosum genome.
- Molluscum contagiosum inhibits host inflammatory response. This unique feature seems to be related to some of the specific genes that are presented in its genome and responsible for shutting down the host immune response.
- Scientists have sequenced more than 190-kilobase pair genome of MCV. These genome findings has now revealed that the virus potentially encodes approximately 182 proteins, 105 of which have direct counterparts in orthopoxviruses (OPV)[1]. 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. MCV have 59 genes that are predicted to encode previously uncharacterized proteins, including major histocompatibility complex class I, chemokine, and glutathione peroxidase homologs, which suggests that there are MCV-specific strategies for coexistence with the human host.[3]
Associated Conditions
- There is a problem with the molluscum contagiosum diagnosis as it is not possible to grow the virus in standard cell culture or in an animal model of infection.
- There are a few reports of some success in growing molluscum contagiosum with the human foreskin xenograft fragments culturing, but it is still under further investigation.[1]
Gross Pathology
- In dermoscopic exam of infected tissue, a central umbilication with polylobular, white to yellow amorphous structures is visualized which is typical for diagnosis. Also a peripheral crown of radiating or punctiform vessels may be seen as well.
- This section is a good place to include pictures. Search for copyleft images on The Pathology Wiki [3] and Ask Dr. Wiki [4].
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
References
- ↑ 1.0 1.1 1.2 Fife KH, Whitfeld M, Faust H, Goheen MP, Bryan J, Brown DR (1996). "Growth of molluscum contagiosum virus in a human foreskin xenograft model". Virology. 226 (1): 95–101. doi:10.1006/viro.1996.0631. PMID 8941326.
- ↑ Bugert JJ, Darai G (1997). "Recent advances in molluscum contagiosum virus research". Arch. Virol. Suppl. 13: 35–47. PMID 9413524.
- ↑ Senkevich TG, Koonin EV, Bugert JJ, Darai G, Moss B (1997). "The genome of molluscum contagiosum virus: analysis and comparison with other poxviruses". Virology. 233 (1): 19–42. doi:10.1006/viro.1997.8607. PMID 9201214.