Molluscum Contagiosum

Introduction

Molluscum contagiosum is a common, benign viral skin infection caused by a poxvirus. It is characterised by the appearance of small, flesh-coloured, dome-shaped papules with a central dimple (umbilication). The condition is generally self-limiting but can be persistent, particularly in immunocompromised individuals. Molluscum contagiosum primarily affects children but can also be seen in adults, particularly those with compromised immune systems or those who are sexually active.

Aetiology and Pathophysiology

Molluscum contagiosum is caused by the molluscum contagiosum virus (MCV), a DNA virus belonging to the poxvirus family. There are several subtypes of the virus, with MCV-1 being the most common:

• Transmission: The virus is spread through direct skin-to-skin contact, including sexual contact, or indirectly through fomites such as towels or clothing. It can also spread by autoinoculation, where the virus is transferred from one part of the body to another through scratching or shaving.
• Incubation Period: The incubation period ranges from 2 to 6 weeks, though it can be longer.
• Risk Factors: The condition is more common in children, sexually active adults, and immunocompromised individuals. Those with atopic dermatitis are also at increased risk due to the compromised skin barrier.

Clinical Presentation

Molluscum contagiosum typically presents with the following features:

• Papules: Small (2-5 mm), flesh-coloured, or pearly-white, dome-shaped papules with a characteristic central umbilication.
• Distribution: The lesions can occur anywhere on the body but are most commonly found on the face, trunk, and extremities in children. In adults, lesions may be found on the lower abdomen, inner thighs, and genital area.
• Number of Lesions: The number of lesions can vary from a few to several hundred, depending on the individual's immune response and the extent of autoinoculation.
• Asymptomatic or Mildly Itchy: The lesions are usually asymptomatic, though mild pruritus (itching) may occur. Secondary bacterial infection can result from scratching.
• Resolution: Lesions typically resolve spontaneously within 6 to 12 months, but they can persist for up to several years, particularly in immunocompromised individuals.

Diagnosis

The diagnosis of molluscum contagiosum is usually clinical, based on the characteristic appearance of the lesions. However, certain tests can confirm the diagnosis if needed:

• Clinical Examination: The typical appearance of dome-shaped papules with central umbilication is often sufficient for diagnosis.
• Dermatoscopy: Dermatoscopy can reveal characteristic central umbilication and white or yellowish inclusions within the lesions.
• Histopathology: In uncertain cases, a biopsy can be performed. Histopathology typically shows molluscum bodies (large eosinophilic cytoplasmic inclusions) within the epidermis.

Management and Treatment

Molluscum contagiosum is generally a self-limiting condition, and in many cases, no treatment is necessary. However, treatment may be considered in cases where lesions are symptomatic, extensive, cosmetically concerning, or in immunocompromised patients:

1. Observation

• Watchful Waiting: As the condition often resolves spontaneously, watchful waiting is appropriate for most patients, particularly children. Parents and patients should be reassured about the benign nature of the condition.

2. Physical Treatments

• Cryotherapy: Liquid nitrogen can be used to freeze the lesions, which causes them to blister and eventually fall off. This method may require multiple treatments and can be painful.
• Curettage: The lesions can be scraped off with a curette. This method is effective but can be uncomfortable, and there is a risk of scarring.
• Laser Therapy: Pulsed dye lasers can be used to target the lesions, particularly in cases where other treatments have failed or are not suitable.

3. Prevention of Spread

• Avoid Sharing Personal Items: Patients should be advised not to share towels, clothing, or other personal items to prevent the spread of the virus.
• Avoid Scratching: Encourage patients to avoid scratching the lesions to prevent autoinoculation and secondary bacterial infection.
• Good Hygiene Practices: Regular hand washing and avoiding contact with lesions can help reduce transmission to others.

When to Refer

Referral to a dermatologist or specialist may be necessary in the following situations:

• Immunocompromised Patients: Patients with HIV/AIDS or other immunosuppressive conditions who develop extensive or persistent molluscum contagiosum should be referred for specialist management.
• Refractory or Extensive Lesions: If the lesions do not respond to treatment or are widespread and causing significant discomfort or cosmetic concern, referral is recommended.
• Uncertain Diagnosis: If the diagnosis is unclear or if there is a suspicion of another condition, such as basal cell carcinoma or verrucae, a referral for further evaluation is advised.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Molluscum Contagiosum. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Molluscum Contagiosum: Diagnosis and Treatment. Available at: https://www.nice.org.uk/guidance/ng198 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical Treatments for Viral Skin Infections. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).