Changes

March 2022 — reviewed. A literature search was conducted in March 2022 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of the topic. No changes to clinical recommendations have been made. A section on Risk factors has been added to Background information.

Update

Goals

To support primary healthcare professionals to:

• Make an accurate diagnosis of molluscum contagiosum.
• Provide appropriate information and advice to people with molluscum contagiosum.
• Treat people with molluscum contagiosum in primary care if needed.
• Refer adults with molluscum contagiosum to genitourinary medicine for screening for sexually transmitted infections.
• Assess the severity of molluscum contagiosum and arrange onwards referral to a specialist where appropriate.

Outcome measures

Audit criteria

QOF indicators

QIPP - Options for local implementation

No QIPP indicators were found during the review of this topic.

NICE quality standards

No NICE quality standards were found during the review of this topic.

What is it?

• Molluscum contagiosum is a viral skin infection caused by the molluscum contagiosum virus (MCV), which is classified within the family of poxviruses (Poxviridae) [van der Wouden, 2017]. 
  • There are four distinct subtypes of MCV. MCV-1 is the most common subtype (75–96% of cases), followed by, in the order of decreasing frequency, MCV-2, MCV-4, and MCV-3 [BASHH, 2014; Leung, 2017; Meza-Romero, 2019; Gaurav, 2021]. 
  • There appears to be no clinical difference between MCV subtypes or their preferred anatomical sites [BASHH, 2014]. An individual infection is usually caused by only one subtype of the virus [BASHH, 2014; Leung, 2017]: 
    • MCV-1 causes almost all paediatric cases of molluscum contagiosum.
    • MCV-2 affects teenagers and adults and is mainly sexually transmitted. It is relatively common in immunocompromized people and accounts for approximately 60% of cases in people with HIV infection [Leung, 2017].
  • Transmission of MCV occurs by direct contact with infected skin (sexual, non-sexual, or autoinoculation) or indirectly via contaminated fomites (such as shared towels and flannels) [Gerlero, 2018; Meza-Romero, 2019]. Vertical transmission has also been reported [BMJ, 2021]. 
  • The incubation period usually ranges from 2–12 weeks but can be as long as 26 weeks [Leung, 2017; Gerlero, 2018; Meza-Romero, 2019; Gaurav, 2021].  
  • Unlike the herpes virus, MCV does not persist as a latent infection [Gerlero, 2018]. Therefore, molluscum contagiosum associated with HIV does not represent recurrence of childhood MCV infection [Leung, 2017].
  • Replication of the virus in infected cells causes hyperplasia and development of the characteristic flesh-coloured, umbilicated papules.

What are the risk factors for molluscum contagiosum?

• Risk factors for molluscum contagiosum include:
  • Close contact with an infected person — transmission occurs by direct contact with infected skin (sexual, non-sexual, or autoinoculation) or indirectly via contaminated fomites (such as shared towels and flannels) [Gerlero, 2018; Meza-Romero, 2019]. Vertical transmission has also been reported [BMJ, 2021]. 
  • Atopic dermatitis — people with atopic dermatitis are more likely to develop infections with molluscum contagiosum due to impaired skin barrier function and immune dysregulation. The prevalence of molluscum contagiosum in children with atopic dermatitis is estimated to be between 20–45% [BMJ, 2021] compared with 5–12% in children who do not have the condition. 
  • Immunocompromize — molluscum contagiosum is particularly problematic in adults who are immunocompromized. The main causes of immunosuppression associated with molluscum contagiosum include HIV infection, solid organ transplants, immunosuppressive therapy, systemic lupus erythematosus, sarcoidosis, and neoplasia. Giant nodules of molluscum contagiosum have been described as a first clinical manifestation of HIV infection. 
  • Climate — molluscum contagiosum is more common in geographical areas with warm climates [Olsen, 2014a; Leung, 2017; BMJ, 2021]. 
  • Swimming — there is evidence for an association between swimming and molluscum contagiosum infection [Olsen, 2014a; BMJ, 2021]. 

How common is it?

• Molluscum contagiosum is common, but the exact prevalence is uncertain as many people never seek medical care.
  
  • In children, the annual incidence of molluscum contagiosum ranges from 2–10% and its prevalence from 5–12%. However, these rates vary significantly depending on the population studied [Gerlero, 2018; BMJ, 2021]. Infection acquired through routine physical contact or, occasionally, fomites is the most common presentation, and children account for most infections [BASHH, 2014].
  • Sexual transmission usually affects young adults and is a very small proportion of reported infections, although it appears to be increasing in frequency [BASHH, 2014].
  • Severe molluscum infection can manifest in the context of immunocompromize [BASHH, 2014]. People with HIV infection are particularly prone to molluscum contagiosum, and prevalence in this population has been reported to range from 5–18% [van der Wouden, 2017].
  • There is no significant difference in the prevalence between males and females, or in different ethnic groups [Olsen, 2014b; BMJ, 2021]. 
• Most studies on molluscum contagiosum have looked at selected populations, such as people attending genito-urinary medicine clinics or dermatology outpatient departments.
  
  • A large UK general practice-based survey of patients' records found that [Pannell et al, 2005]:
    • The average annual incidence of new presentations of molluscum was 261/100,000.
    • The annual incidence of new presentations of molluscum in children aged 0–14 years was 1265/100,000.
    • Over 80% of reported cases occurred in children aged under 15 years, with the maximum incidence in preschool children aged 1–4 years.
    • In a general practice population of 10,000 people, about 24 new cases of molluscum contagiosum present each year.
  • A retrospective longitudinal study in primary care found that from 2004 to 2013 [Olsen, 2016]:
    • The incidence of molluscum in children presenting to their GP was 2 in 1000 person-years in those aged younger than 1 year, 13–14 in 1000 person-years in those aged 1–9 years, and 4–5 in 1000 person-years in those aged 10–14 years.
    •  The rate of molluscum consultations in primary care for children aged 0–14 years was 9.5 per 1000 person-years. 
    • The highest consultation rates were in those aged 1–4 years and 5–9 years for both males and females. Consultation rates for males were marginally higher in those aged 1–4 years (13.1 per 1000) than in those aged 5–9 years (13.0 per 1000). However, for females the highest rate of consultations was in those aged 5–9 years (13.9 per 1000) and 1–4 years (13.0 per 1000).
    • Consultation rates for molluscum contagiosum declined by 50% from 2004 to 2013. 

What are the complications?

• Complications from molluscum contagiosum include [Olsen, 2014a; Leung, 2017; Meza-Romero, 2019; Edwards, 2020; BMJ, 2021]:
  • Emotional and psychological distress — arising from the cosmetic appearance of the lesions.
  • Skin reactions — pruritus and erythema occur in about 30% of people with molluscum contagiosum, especially those with atopic dermatitis. Resolution of molluscum may take longer in people with atopic dermatitis [BMJ, 2021]. Erythema multiforme and erythema annulare centrifugum (a widespread rash of red inflammatory rings) have rarely been reported [Leung, 2017; van der Wouden, 2017].
  • Scarring — occurs in about 7% of people with molluscum contagiosum. It heals naturally and is rarely permanent. Scaring may be caused by the body's immune response or by the use of phenol, which is no longer recommended.
  • Bacterial superinfection — secondary bacterial infection may be caused by local entry of bacteria into the skin at the site of molluscum. Scratching of molluscum will compromise the skin barrier and increase the chance of bacterial infection, especially in children with atopic dermatitis. The molluscum contagiosum virus can cause folliculitis in immunocompromized people (molluscum folliculitis) [Gaurav, 2021]. Infection of an epidermoid cyst by the molluscum contagiosum virus has rarely been reported [Leung, 2017].
  • Ocular complications — lesions on the lid margins may shed viral toxins into the conjunctival sac, causing follicular conjunctivitis and, uncommonly, corneal involvement [The College of Optometrists, 2021].
  • Hypersensitivity reaction — in about 10% of people, molluscum lesions may be surrounded by a halo of eczema (molluscum dermatitis). This is the result of a hypersensitivity reaction to the viral antigen and can evolve into an abscess or a less morphologically typical lesion [Leung, 2017; Gerlero, 2018; Gaurav, 2021]. 

What is the prognosis?

• Molluscum contagiosum is a benign and usually self-limiting infection [Gerlero, 2018].
  • In otherwise healthy people, the prognosis is extremely good [BMJ, 2021].
    • Most lesions resolve spontaneously, and complications are uncommon.
    • Spontaneous resolution usually occurs within 18 months, but in some cases the lesions may persist for more than 3 or 4 years [Olsen, 2014a; Leung, 2017; van der Wouden, 2017].
    • Lesions tend to last longer in people with co-existing atopic dermatitis [Leung, 2017; NHS Lothian, 2020].
  • In people who are immunocompromized, individual molluscum contagiosum lesions can persist for longer (5 years or more) [Bhatia, 2012; NHS Lothian, 2020].
    • Immunocompromized people may manifest hundreds of lesions with rapid spread, depending on their level of immunosuppression. In people with HIV infection, clearance may be delayed or incomplete but may improve with treatment [BMJ, 2021].

How should I diagnose molluscum contagiosum?

• The diagnosis of molluscum contagiosum is predominantly clinical, as the classic appearance of the lesions usually excludes other conditions, such as warts. Diagnostic investigations are not usually necessary. 
  
  • Typically, the person presents with lesions which have developed over a few weeks.
    • The lesions are usually characteristic, presenting as smooth-surfaced, firm, dome-shaped, flesh-coloured or pearly white papules with a central umbilication. 
    • Commonly, people have 1–30 individual lesions at a time, occurring as clusters (which can become koebnerised). Occasionally, solitary lesions can be seen.
    • Molluscum lesions are usually 2–5 mm in diameter. Occasionally, much larger (giant mollusca) lesions (1 cm or greater in diameter) can be seen, especially with solitary lesions or in the setting of immunocompromize.
  • Almost any part of the body can be affected:
    • In children, lesions are commonly seen on the trunk and in flexures, but anogenital lesions may also occur.
    • In adults, sexual contact may lead to lesions developing on the genitalia, pubis, thighs, and lower abdomen.
    • Rarely, lesions can occur on the soles of the feet, palms of the hands, oral mucosa, and eyelids. 
    • Immunocompromized people (for example those with HIV) or people on immunosuppressants (such as oral corticosteroids) can present with facial, widespread (often numbering over 100), or atypical lesions.
    • Atypical presentations may include giant, cystic, ulcerated, follicular, condyloma acuminatum-like, sebaceous naevus-like, pyogenic granuloma-like, cellulitis or abscess-like lesions.
  • Molluscum lesions are frequently asymptomatic, but complications (such as pruritus, erythema and bacterial superinfection) may occur
    
    • Eczema or inflammation can develop around lesions prior to resolution. It is important to differentiate this from inflammation from eczema or a bacterial skin infection, both of which may require treatment.

What else might it be?

• Differential diagnoses of molluscum contagiosum include:
  
  • Acne vulgaris.
  • Infections, such as common warts (verruca vulgaris), chicken pox, folliculitis, and condyloma acuminatum. See the CKS topics on Warts - anogenital  and Warts and verrucae.
  • Milia.
  • Keratoacanthoma.
  • Cutaneous horn.
  • Tumours, such as basal cell carcinoma and syringomas.
  • Papular urticaria.
  • Lichen planus (uncommon).
  • Deep fungal infection, including penicilliosis, cryptococcosis, histoplasmosis, coccidiodomycosis, pneumocystis carinii, and aspergillosis.
• Differential diagnoses of genital molluscum include:
  • Ectopic sebaceous glands.
  • Vulvar lymphangioma circumscriptum.
  • Genital warts.
• Differential diagnoses of giant molluscum contagiosum include: 
  • Acantholytic acanthoma.
  • Epidermoid cyst.
  • Subepidermal calcified nodule.
  • Abscess.
  • Keratoacanthoma.
  • Cutaneous horn.

Scenario: Management of molluscum contagiosum

From age 1 month onwards.

Search strategy

Scope of search

A literature search was conducted for guidelines, systematic reviews and randomized controlled trials on primary care management of molluscum contagiosum in children and adults.

Search dates

March 2017 - January 2022

Key search terms

Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline.

• exp Molluscum contagiosum virus/, exp Molluscum Contagiosum/, molluscum.tw  pox virus.kw.

Sources of guidelines

• National Institute for Health and Care Excellence (NICE)
• Scottish Intercollegiate Guidelines Network (SIGN)
• Royal College of Physicians
• Royal College of General Practitioners
• Royal College of Nursing
• NICE Evidence
• World Health Organization
• Guidelines International Network
• TRIP database
• Agency for Healthcare Research and Quality
• Institute for Clinical Systems Improvement
• National Health and Medical Research Council (Australia)
• Royal Australian College of General Practitioners
• British Columbia Medical Association
• Canadian Medical Association
• Alberta Medical Association
• Michigan Quality Improvement Consortium
• Singapore Ministry of Health
• National Resource for Infection Control
• RefHELP NHS Lothian Referral Guidelines
• Medline (with guideline filter)
• Driver and Vehicle Licensing Agency
• NHS Health at Work (occupational health practice)

Sources of systematic reviews and meta-analyses

• The Cochrane Library:
  • Systematic reviews
  • Protocols
  • Database of Abstracts of Reviews of Effects
• Medline (with systematic review filter)
• EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

• NIHR Health Technology Assessment programme
• The Cochrane Library:
  • NHS Economic Evaluations
  • Health Technology Assessments
• Canadian Agency for Drugs and Technologies in Health
• International Network of Agencies for Health Technology Assessment

Sources of randomized controlled trials

• The Cochrane Library:
  • Central Register of Controlled Trials
• Medline (with randomized controlled trial filter)
• EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

• Bandolier
• Drug and Therapeutics Bulletin
• TRIP database
• Central Services Agency COMPASS Therapeutic Notes

Sources of national policy

• Department of Health
• Health Management Information Consortium (HMIC)

Patient experiences

• Healthtalk
• BMJ - Patient Journeys

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

• British National Formulary (BNF)
• electronic Medicines Compendium (eMC)
• European Medicines Agency (EMEA)
• LactMed
• Medicines and Healthcare products Regulatory Agency (MHRA)
• REPROTOX
• Scottish Medicines Consortium
• Stockley's Drug Interactions
• TERIS
• TOXBASE
• Micromedex
• UK Medicines Information

Stakeholder engagement

Our policy

The external review process is an essential part of CKS topic development. Consultation with a wide range of stakeholders provides quality assurance of the topic in terms of:

• Clinical accuracy.
• Consistency with other providers of clinical knowledge for primary care.
• Accuracy of implementation of national guidance (in particular NICE guidelines).
• Usability.

Principles of the consultation process

• The process is inclusive and any individual may participate.
• To participate, an individual must declare whether they have any competing interests or not. If they do not declare whether or not they have competing interests, their comments will not be considered.
• Comments received after the deadline will be considered, but they may not be acted upon before the clinical topic is issued onto the website.
• Comments are accepted in any format that is convenient to the reviewer, although an electronic format is encouraged.
• External reviewers are not paid for commenting on the draft topics.
• Discussion with an individual or an organization about the CKS response to their comments is only undertaken in exceptional circumstances (at the discretion of the Clinical Editor or Editorial Steering Group).
• All reviewers are thanked and offered a letter acknowledging their contribution for the purposes of appraisal/revalidation.
• All reviewers are invited to be acknowledged on the website. All reviewers are given the opportunity to feedback about the external review process, enabling improvements to be made where appropriate.

Stakeholders

• Key stakeholders identified by the CKS team are invited to comment on draft CKS topics. Individuals and organizations can also register an interest to feedback on a specific topic, or topics in a particular clinical area, through the Getting involved section of the Clarity Informatics website.
• Stakeholders identified from the following groups are invited to review draft topics:
  • Experts in the topic area.
  • Professional organizations and societies (for example, Royal Colleges).
  • Patient organizations, Clarity has established close links with groups such as Age UK and the Alzheimer’s Society specifically for their input into new topic development, review of current topic content and advice on relevant areas of expert knowledge.
  • Guideline development groups where the topic is an implementation of a guideline.
  • The British National Formulary team.
  • The editorial team that develop MeReC Publications.
• Reviewers are provided with clear instructions about what to review, what comments are particularly helpful, how to submit comments, and declaring interests.

Patient engagement

Clarity Informatics has enlisted the support and involvement of patients and lay persons at all stages in the process of creating the content which include:

• Topic selection
• Scoping of topic
• Selection of clinical scenarios
• First draft internal review
• Second draft internal review
• External review
• Final draft and pre-publication

Our lay and patient involvement includes membership on the editorial steering group, contacting expert patient groups, organizations and individuals.

Evidence exclusion criteria

Our policy

Scoping a literature search, and reviewing the evidence for CKS is a methodical and systematic process that is carried out by the lead clinical author for each topic. Relevant evidence is gathered in order that the clinical author can make fully informed decisions and recommendations. It is important to note that some evidence may be excluded for a variety of reasons. These reasons may be applied across all CKS topics or may be specific to a given topic.

Studies identified during literature searches are reviewed to identify the most appropriate information to author a CKS topic, ensuring any recommendations are based on the best evidence. We use the principles of the GRADE and PICOT approaches to assess the quality of published research. We use the principles of AGREE II to assess the quality of published guidelines.

Standard exclusions for scoping literature:

• Animal studies
• Original research is not written in English

Possible exclusions for reviewed literature:

• Sample size too small or study underpowered
• Bias evident or promotional literature
• Population not relevant
• Intervention/treatment not relevant
• Outcomes not relevant
• Outcomes have no clear evidence of clinical effectiveness
• Setting not relevant
• Not relevant to UK
• Incorrect study type
• Review article
• Duplicate reference

Organizational, behavioural and financial barriers

Our policy

The CKS literature searches take into consideration the following concepts, which are discussed at the initial scoping of the topic.

• Feasibility
  • Studies are selected depending on whether the intervention under investigation is available in the NHS and can be practically and safely undertaken in primary care.
• Organizational and Financial Impact Analysis
• Studies are selected and evaluated on whether the intervention under investigations may have an impact on local clinical service provision or national impact on cost for the NHS. The principles of clinical budget impact analysis are adhered to, evaluated and recorded by the author. The following factors are considered when making this assessment and analysis.
  • Eligible population
  • Current interventions
  • Likely uptake of new intervention or recommendation
  • Cost of the current or new intervention mix
  • Impact on other costs
  • Condition-related costs
  • In-direct costs and service impacts
  • Time dependencies
• Cost-effectiveness or cost-benefit analysis studies are identified where available. 

We also evaluate and include evidence from NICE accredited sources which provide economic evaluations of recommendations, such as NICE guidelines. When a recommended action may not be possible because of resource constraints, this is explicitly indicated to healthcare professionals by the wording of the CKS recommendation.

Declarations of interest

Our policy

Clarity Informatics requests that all those involved in the writing and reviewing of topics, and those involved in the external review process to declare any competing interests. Signed copies are securely held by Clarity Informatics and are available on request with the permission of the individual. A copy of the declaration of interest form which participants are asked to complete annually is also available on request. A brief outline of the declarations of interest policy is described here and full details of the policy is available on the Clarity Informatics website. Declarations of interests of the authors are not routinely published, however competing interests of all those involved in the topic update or development are listed below. Competing interests include:

• Personal financial interests
• Personal family interest
• Personal non-financial interest
• Non-personal financial gain or benefit

Although particular attention is given to interests that could result in financial gains or losses for the individual, competing interests may also arise from academic competition or for political, personal, religious, and reputational reasons. An individual is not obliged to seek out knowledge of work done for, or on behalf of, the healthcare industry within the departments for which they are responsible if they would not normally expect to be informed.

Who should declare competing interests?

Any individual (or organization) involved in developing, reviewing, or commenting on clinical content, particularly the recommendations should declare competing interests. This includes the authoring team members, expert advisers, external reviewers of draft topics, individuals providing feedback on published topics, and Editorial Steering Group members. Declarations of interest are completed annually for authoring team and editorial steering group members, and are completed at the start of the topic update and development process for external stakeholders.

Competing interests declared for this topic:

None.