Chapter 317. Molluscum Contagiosum

Molluscum contagiosum is a cutaneous viral infection caused by the poxvirus Molluscipoxvirus, an approximately 300-nm, double-stranded DNA, brick-shaped virus. Humans are the only known source of the virus, which is spread by direct contact, including sexual contact, autoinoculation, or contaminated fomites. Molluscum can be seen at any age, but are most common in children younger than 8 years. Outbreaks have been noted among wrestlers and in pools and water parks. Patients with atopic dermatitis and immunosuppressed individuals, including persons with HIV infection, tend to have more intense and widespread eruptions, but most children presenting with molluscum contagiosum are otherwise healthy and immunocompetent.1,2

Clinical Manifestations and Diagnosis

Molluscum contagiosum is usually asymptomatic, although an eczematous, red, scaling patch may surround lesions in about 10% of patients, and is termed molluscum dermatitis. Molluscum are usually diagnosed clinically, based on morphology and distribution. Flat-topped, discrete, dome-shaped, flesh-colored lesions are usually 1 to 5 mm in diameter. Central white cores or umbilication are seen in active lesions (Fig. 367-5). Molluscum lesions commonly occur on the trunk, face, and extremities, but may be generalized.2 Groups of lesions often occur in body folds and intertriginous areas, secondary to skin-to-skin autoinoculation. Small, atypical, and giant lesions may be mistaken for verrucae, keratosis pilaris, milia, bacterial pustules, or cutaneous papules, such as juvenile xanthogranuloma.

Contents of the central core, obtained by needle extraction and examined microscopically after staining with Wright or Giemsa stain, display molluscum bodies, distinctive ovoid intracytoplasmic inclusions.

Treatment

Molluscum contagiosum infection is usually self-limited, with the disease duration quite variable, lasting several weeks to several years. Lesions can regress spontaneously, but treatment may prevent autoinoculation and spread to other individuals. Chemical or physical destruction is commonly used to treat molluscum though the evidence basis of treatments is limited. Chemical treatments include cantharidin (0.7% in collodion), tretinoin, imiquimod, salicylic acid, and lactic acid. Physical destruction using liquid nitrogen cryotherapy or removal of the central core using curettage or needle extraction of each lesion usually results in resolution (Table 367-2). Small pitted scars are rare, but may occur spontaneously or secondary to treatment.3-6 Generally, reassurance that the condition is self-limited is a reasonable approach, although topical therapy with tretinoin or other chemical agent can be considered. Referral to a dermatologist can be considered for persistent molluscum, large numbers of lesions on an individual, or patient or family preference, with cantharidin or curettage most commonly used.

Prevention

Children with lesions covered by clothing have a very low risk of spreading disease to others. Because infection may spread in water, families should be advised not to have siblings bathe together if an affected child has active lesions. In outbreaks (eg, among wrestlers), spread may be decreased by restricting body contact and by restricting the sharing of potential contaminated fomites (eg, towels).