Overview
Definition:
Molluscum contagiosum (MC) is a common, benign, viral skin infection caused by the *Molluscipoxvirus*
It presents as discrete, dome-shaped papules with a central umbilication.
Epidemiology:
It is highly contagious and most common in children aged 1 to 10 years
Prevalence varies geographically, but it affects millions worldwide annually
Transmission occurs via direct skin-to-skin contact, fomites, or autoinoculation.
Clinical Significance:
While often self-limiting, MC can cause significant cosmetic concerns, psychosocial distress, and pruritus, especially in immunocompromised individuals
Understanding treatment indications is crucial for effective patient management and to prevent complications and spread.
Clinical Presentation
Symptoms:
Asymptomatic lesions are most common
Pruritus can occur
Lesions may become inflamed or secondarily infected
Discomfort or pain may arise if lesions are in intertriginous areas or become infected.
Signs:
Lesions are typically 2-5 mm in diameter, pearly or skin-colored papules with central umbilication
They can be solitary or multiple, disseminated, or grouped
Lesions are commonly found on the trunk, face, extremities, and genital areas
In immunocompromised individuals, lesions can be larger, more widespread, and atypical.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on the characteristic appearance of umbilicated papules
Biopsy with histopathological examination and PCR for molluscum contagiosum virus DNA can confirm diagnosis in ambiguous cases, though rarely needed for typical presentations.
Diagnostic Approach
History Taking:
Inquire about the onset, duration, and spread of lesions
Ask about any pruritus, pain, or signs of secondary infection
Assess for immunocompromise (e.g., HIV, chemotherapy, chronic steroid use) or atopy, which can influence lesion behavior
Note recent travel, contact with affected individuals, or use of shared items.
Physical Examination:
Perform a thorough dermatological examination to assess the number, size, distribution, and morphology of the lesions
Examine the entire skin surface, including the scalp, face, trunk, extremities, and genital/perianal areas
Look for signs of inflammation, excoriation, or secondary bacterial infection.
Investigations:
Generally not required for typical cases in immunocompetent children
In immunocompromised patients or cases with diagnostic uncertainty, a skin biopsy for histopathology (showing eosinophilic cytoplasmic inclusions called molluscum bodies) or PCR can be considered.
Differential Diagnosis:
Important differential diagnoses include viral warts, lichen planus, folliculitis, acne, milia, benign nevi, and basal cell carcinoma
Unique umbilication is a key distinguishing feature of MC.
When To Treat
Indications For Treatment:
Treatment is generally recommended for cosmetic concerns, significant pruritus, symptoms of inflammation or secondary infection, rapid spread, or in immunocompromised individuals where lesions may be extensive and persistent
Also consider treatment if lesions are causing significant psychosocial distress.
Age Considerations:
In infants and very young children, spontaneous resolution is common, and observation may be preferred unless lesions are bothersome or spreading rapidly
In older children and adolescents, cosmetic impact and the desire for quicker clearance may favour treatment.
Immunocompromised Patients:
Treatment is strongly advised in immunocompromised individuals due to the potential for widespread, persistent, and debilitating disease, which can be a marker of underlying immunosuppression.
Treatment Goals:
The goals of treatment are to accelerate lesion clearance, reduce transmission, alleviate symptoms (pruritus, inflammation), and improve cosmetic appearance and psychosocial well-being.
Management Options
Observation And Supportive Care:
Reassurance that MC is benign and usually self-limiting within 6-18 months
Advise on good hygiene practices to prevent spread and on emollients for pruritus
Topical treatments like calamine lotion or mild corticosteroids can manage itching.
Topical Therapies:
Potassium hydroxide (KOH) 5-10% solution or gel, topical retinoids (tretinoin, adapalene), salicylic acid preparations, imiquimod cream, and topical cantharidin are options
Application should be careful and localized to lesions to minimize irritation.
Physical Destruction Methods:
Curettage (with or without local anesthesia), cryotherapy (liquid nitrogen), or electrodessication are effective for individual lesions, often used for discrete, bothersome papules
These are typically performed by a healthcare professional.
Pharmacological Treatment:
While no specific antiviral therapy exists for MC, treatments that induce an inflammatory response or cellular turnover are used
Systemic treatments are rarely indicated but may be considered for extensive disease in select cases.
Complications
Secondary Infection:
Bacterial superinfection is common, presenting as erythema, pain, and purulent discharge
Management involves appropriate antibiotics.
Scarring:
Although rare with spontaneous resolution, aggressive treatment or secondary infection can sometimes lead to hyper- or hypopigmentation or minor scarring.
Psychosocial Impact:
The visible nature of the lesions, especially on the face and extremities, can lead to teasing, bullying, and reduced self-esteem in children.
Dissemination:
In immunocompromised individuals, the virus can disseminate widely, leading to extensive and difficult-to-treat lesions.
Key Points
Exam Focus:
Recognize characteristic umbilicated papules
Understand that treatment is not always necessary in immunocompetent children but is indicated for cosmetic concerns, severe pruritus, infection, rapid spread, or immunocompromise
Know the common differentials.
Clinical Pearls:
Emphasize hygiene to prevent spread
Reassure parents about the benign and self-limiting nature of MC in most cases
Be aware of atypical presentations in immunocompromised patients
Consider sequential treatment of lesions to reduce patient discomfort.
Common Mistakes:
Over-treating asymptomatic lesions in immunocompetent children
Misdiagnosing MC as other papular eruptions
Failing to consider underlying immunocompromise when lesions are extensive or persistent.