Molluscum contagiosum overview

# Overview
Molluscum contagiosum is a common disease that mostly affect children in preschool age and school aged children as well. Outbreaks of molluscum contagiosum have occurred in the different settings like swimming pools. Molluscum contagiosum may be classified according to virus sub-types based on restriction endonuclease analysis into 4 different subtypes. There is not enough evidence about correlation of molluscum contagiosum subtypes and the disease features or anatomical distribution of lesions. 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. he most important risk factors associated with molluscum contagiosum include: childhood age, closer contact sports, swimming-pool attendance , sexual relationship and multiple sexual partners, immunodeficient statessuch as inherited immunodeficiencies, human immunodeficiency virus (HIV) infection, and following treatment with immunosuppressive drugs. The hallmark of molluscum contagiosum is 2 to 5 mm in diameter lesions that spares over hands and feet. The mainstay of therapy for molluscum contagiosum is topical treatment.

# Historical perspective
Molluscum contagiosum was first discovered by Bateman in 1817 in his second edition of his synopsis. In 1841 Paterson demonstrated molluscum contagiosum's infectious nature. The viral nature of the disease was demonstrated by Juliusberg in 1905. Outbreaks of molluscum contagiosum have occurred in the different settings like swimming pools, but the exact information about outbreaks is not available due to report policy.

# Classification
Molluscum contagiosum may be classified according to virus sub-types based on restriction endonuclease analysis into 4 different subtypes. 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. There is not enough evidence about correlation of molluscum contagiosum subtypes and the disease features or anatomical distribution of lesions.

# Pathophysiology
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.

# Differentiating tonsillitis from other diseases
Molluscum contagiosum must be differentiated from other diseases that cause infection of the skin and of the mucous membranes. Skin lesions due to cryptococcosis, histoplasmosis, or Penicillium marneffei infection may resemble molluscum lesions. Other lesions that may be mistaken from molluscum contagiosum include flat warts, condyloma acuminatum, pyogenic granuloma , adnexal tumors, Langerhans cell histiocytosis , basal cell carcinoma , and amelanotic melanoma. Skin biopsy is useful for distinguishing molluscum contagiosum from other disorders.

# Epidemiology and Demographics
The prevalence of molluscum contagiosum is estimated to be around 8000 cases per 100,000 annually. Worldwide, the incidence of molluscum contagiosum is 1200-1400 per 100,000 persons. Molluscum contagiosum is a common disease that tends to affect children and immunocompromised. There is no racial predilection to molluscum contagiosum. There is no gender predilection to molluscum contagiosum.

# Risk Factors
The most important risk factors associated with molluscum contagiosum include: childhood age, closer contact sports, swimming-pool attendance , sexual relationship and multiple sexual partners, immunodeficient statessuch as inherited immunodeficiencies, human immunodeficiency virus (HIV) infection, and following treatment with immunosuppressive drugs. 

# Screening
There is insufficient evidence to recommend routine screening for molluscum contagiosum. Molluscum Contagiosum Diagnostic Tool for Parents (MCDTP) is a new developed diagnostic test for in home diagnosis of the molluscum contagiosum in children but it is not recommended by guidelines as a routine screening test. There is no guideline recommendation for screening of molluscum contagiosum in suspected cases.

# Natural history, complications and prognosis

## Natural History
The symptoms of molluscum contagiosum usually develop 2 to 7 weeks after exposure but may range from 1 week to 6 months, with a mean of 6 weeks. Molluscum contagiosum start with symptoms such as rash and pruritis. Molluscum contagiosum is a self-limited disease that can be resolved even without treatment. Occasionally, disease may persists for up to three to five years. 

## Complications
Complications that can develop as a result of Molluscum contagiosum is skin scarring (which usually may happen after spontaneous resolution),  chronic conjunctivitis or keratoconjunctivitis, and rarely Gianotti-Crosti like eruptions. Inflammatory reactions to molluscum contagiosum antigen has been reported.

## Prognosis
The prognosis of molluscum contagiosum is good even without treatment.

# Diagnosis

## Diagnostic criteria
There are no criteria for the diagnosis of molluscum contagiosum. Although the diagnosis is usually based on characteristic appearance of the lesions, diagnostic studies that can be used include histologic examination, dermoscopic examination and electron microscopy of biopsies.

## History and Symptoms
The hallmark of molluscum contagiosum is 2 to 5 mm in diameter lesions that spares over hands and feet. A positive history of swimming-pool attendance, sexual multiple partners, and endemic infection are suggestive of molluscum contagiosum. The most common symptoms of molluscum contagiosum include shiny surface skin lesions, may be associated with erythema around the lesion and pruritus.  Less common symptoms of molluscum contagiosum include conjunctivitis, and erythema in all the body.

## Physical Examination
Patients with molluscum contagiosum usually appear good and healthy. Physical examination of patients with molluscum contagiosum is usually remarkable for skin papules that are small, shiny and firm.

## Laboratory Findings
There are no diagnostic lab findings associated with molluscum contagiosum. The diagnosis of molluscum contagiosum should be made clinically. For confirmation of the diagnosis, pathological studies can be done which involve Hematoxylin and Eosin staining of the infected tissue and direct visualization. it is also recommended to test for other sexually transmitted diseases in adults and for immunodeficiency related diseases.

## Imaging Findings
Molluscum contagiosum can also be diagnosed with dermoscopic evaluation of infected tissue. In dermoscopic exam of infected tissue, a central umbilication with poly-lobular, 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.

# Treatment

## Medical Therapy
The mainstay of therapy for molluscum contagiosum is topical treatment. Contemporary medical therapies for molluscum contagiosum are based on topical application of caustic agents including cantharidin, podophyllotoxin, imiquimod, and potassium hydroxide. Cryotherapy is another topical therapy that involve liquid nitrogen application with a cotton-tipped swab to the lesion.

## Surgery
Surgical treatments include curettage, in which molluscum contagiosum lesions are removed with a surgical knife. Also laser therapy can be effective in the treatment of molluscum contagiosum lesions.

# Prevention

## Primary Prevention
Effective measures for the primary prevention of molluscum contagiosum include following hygiene (cleanliness) habits, covering lesions, and not to share personal items with others.

## Secondary Prevention
Secondary prevention strategies following molluscum contagiosum include early detection of lesions.