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
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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

This is a common infection in children and occurs when a child comes into direct contact with a lesion. The virus can spread through contact with contaminated objects, such as towels, clothing, or toys. The virus also spreads by sexual contact. Persons with a weakened immune system (due to conditions such as AIDS) may have a rapidly worse case of molluscum contagiosum.

Pathophysiology

The time from infection to the appearance of lesions ranges from 1 week to 6 months, with an average incubation period of 6 weeks. Diagnosis is made on the clinical appearance.

Transmission

In adults, molluscum infections are often sexually transmitted and usually affect the genitals, lower abdomen, buttocks, and inner thighs. In rare cases, molluscum infections are also found on the lips, mouth, and eyelids. It is spread through direct contact or shared articles of clothing (including towels).

Virology

MC has no animal reservoir, infecting only humans, as did smallpox. However, there are different pox viruses that infect many other mammals. The infecting human MC virus is a DNA poxvirus called the molluscum contagiosum virus (MCV). There are 4 types of MCV, MCV-1 to -4, with MCV-1 being the most prevalent and MCV-2 seen usually in adults and often sexually transmitted. The virus cannot routinely be cultured.

Overview

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Template

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Template Sentence 1: [Pathogen name] is usually transmitted via the [transmission route] route to the human host.

Template Sentence 2: Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.

Template Sentence 3: On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Template Sentence 4: On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Template Sentence 5: [Disease name] is transmitted in [mode of genetic transmission] pattern.

Template Sentence 6: [Disease/malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].

Template Sentence 7: Development of [disease name] is the result from multiple genetic mutations.

Template Sentence 8: Genes involved in the pathogenesis of [disease name] include [gene1], [gene2], and [gene3].

Template Sentence 9: The progression to [disease name] usually involves the [molecular pathway].

Template Sentence 10: The pathophysiology of [disease name] depends on the histological subtype.

Pathogenesis

• Molluscum contagiosum is a member of the poxvirus family
• causes a chronic localized infection with small papules on the skin of an infected individual in contrast to the acute, sometimes fatal, disease induced by smallpox.
• the only known host for molluscum is humans
• inability to grow the virus in standard cell culture or in an animal model of infection.
• reports of some success in growth using human foreskin xenograft fragments.
• (MCV) commonly causes asymptomatic cutaneous neoplasms in children and sexually active adults as well as persistent opportunistic acquired immunodeficiency syndrome (AIDS)-associated disease.
• Sequencing the 190-kilobase pair genome of MCV has now revealed that the virus potentially encodes 163 proteins, of which 103 have homologs in the smallpox virus. 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 possesses 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.
• Analysis of the molluscum contagiosum virus (MCV) genome revealed that it encodes approximately 182 proteins, 105 of which have direct counterparts in orthopoxviruses (OPV).
• The corresponding OPV proteins comprise those known to be essential for replication as well as many that are still uncharacterized, including 2 of less than 60 amino acids that had not been previously noted. The OPV proteins most highly conserved in MCV are involved in transcription; the least conserved include membrane glycoproteins. Twenty of the MCV proteins with OPV counterparts also have cellular homologs and additional MCV proteins have conserved functional motifs. Of the 77 predicted MCV proteins without OPV counterparts, 10 have similarity to other MCV proteins and/or distant similarity to proteins of other poxviruses and 16 have cellular homologs including some predicted to antagonize host defenses. Clustering poxvirus proteins by sequence similarity revealed 3 unique MCV gene families and 8 families that are conserved in MCV and OPV. Two unique families contain putative membrane receptors; the third includes 2 proteins, each containing 2 DED apoptosis signal transduction domains. Additional families with conserved patterns of cysteines and putative redox active centers were identified. Promoters, transcription termination signals, and DNA concatemer resolution sequences are highly conserved in MCV and OPV. Phylogenetic analysis suggested that MCV, OPV, and leporipoxviruses radiated from a common poxvirus ancestor after the divergence of avipoxviruses. Despite the acquisition of unique genes for host interactions and changes in GC content, the physical order and regulation of essential ancestral poxvirus genes have been largely conserved in MCV and OPV.
• replicates in the cytoplasm of cells, and thus, it is not surprising that more than one-half of the genes are similar to those found in variola and vaccinia viruses.
• Pathogenesis is the mechanism by which a certain factor causes disease (pathos = disease, genesis = development). The term can also be used to describe the development of the disease, whether it is acute, chronic, or recurrent. It can also be used to describe whether the disease causes inflammation, malignancy,necrosis etc.
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Genetics

• Some diseases are genetic, and have particular inheritance patterns, and express different phenotypes.
• The effect that genetics may have on the pathophysiology of a disease can be described in this section.
• MCV genome was 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 allow the investigation of novel host defense mechanisms and provide new possibilities for the development of therapeutics for treatment and prevention of the MCV infection.
• many genes found in variola and vaccinia are not present in the molluscum contagiosum genome.
• Molluscum contagiosum contains many unique genes that encode proteins responsible for novel host defense mechanisms; these mechanisms inhibit the host inflammatory and immune responses to the infection.

Associated Conditions

• Conditions associated with the disease can be detailed in this section.
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Gross Pathology

• Gross pathology refers to macroscopic or larger scale manifestations of disease in organs, tissues and body cavities. The term is commonly used by pathologist to refer to diagnostically useful findings made during the gross examination portion of surgical specimen processing or an autopsy.
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Microscopic Pathology

• Microscopic pathology is the disease process as it occurs at the microscopic level.
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