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
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.
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.
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).