Molluscum
Info 5
Excerpted from Dermatology
Online Journal
Molluscum Contagiosum
Daniel Hanson and Dayna G. Diven
Dermatology Online Journal 9(2): 2
Primary Health, Boise, Idaho USA
Abstract
Molluscum contagiosum is a disease
caused by a poxvirus of the Molluscipox virus genus that produces
a benign self-limited papular eruption of multiple umbilicated
cutaneous tumors. This common viral disease is confined to
the skin and mucous membranes. Transmission requires direct
contact with infected hosts or contaminated fomites. It is
generally thought to infect humans exclusively, but there
are a few isolated reports of Molluscum contagiosum occurring
in chickens, sparrows, pigeons, chimpanzees, kangaroos, a
dog, and a horse. The infection is found worldwide and has
a higher incidence in children, sexually active adults, and
those who are immunodeficent.
Introduction
Molluscum contagiosum, a cutaneous
and mucosal eruption caused by a Molluscipox virus, was first
described and later assigned its name by Bateman in the beginning
of the nineteenth century.[1] In 1841 Henderson and Paterson
described the intracytoplasmic inclusion bodies now known
as molluscum or Henderson-Paterson bodies.[2] In the early
twentieth century, Juliusberg, Wile, and Kingery were able
to extract filterable virus from lesions and show transmissibility.[3,4]
Goodpasture later described the similarities of molluscum
and vaccinia.[5] Though generally thought to infect only humans,
case reports of the virus occurring in other animals have
been published. [6,7,8,9]
Incidence
Molluscum contagiosum virus (MCV) can
be found worldwide with a higher distribution in the tropical
areas. The disease is more prevalent in children with the
lesions involving the face, trunk, and extremities. In adults
the lesions are most often found near the genital region.
The disease is endemic with a higher incidence within institutions
and communities where overcrowding, poor hygiene, and poverty
potentiate its spread.[10] Over the last 30 years its incidence
has been increasing, mainly as a sexually transmitted disease,
and it is particularly rampant as a result of concurrent human
immunodeficiency virus (HIV) infection.[11] The worldwide
incidence is estimated to be between 2% and 8%.[12] Less then
5% of the children in the United States are believed to be
infected. Between 5% and 20% of patients with HIV have symptomatic
MCV.[13,14] There are four main subtypes of molluscum contagiosum:
MCV I, MCV II, MCV III, and MCV IV.[15,16] All subtypes cause
similar clinical lesions in genital and nongenital regions.
Studies show MCV I to be more prevalent (75%–90%) than
MCV II, MCV III, and MCV IV, except in immunocompromised individuals.[17,18]
There are, however, regional variations in the predominance
of a given subtype and differences between individual subtypes
in different countries.[19]
Pathogenesis
This disease is transmitted primarily
through direct skin contact with an infected individual. Fomites
have been suggested as another source of infection, with molluscum
contagiosum reportedly acquired from bath towels, tattoo instruments,
and in beauty parlors and Turkish baths.[10] The average incubation
time is between 2 and 7 weeks with a range extending out to
6 months. Infection with the virus causes hyperplasia and
hypertrophy of the epidermis.[12] Free virus cores have been
found in all layers of the epidermis. So-called viral factories
are located in the malpighian and granular cell layers.[12]
The molluscum bodies contain large numbers of maturing virions.
These are contained intracellularly in a collagen-lipid-rich
saclike structure that is thought to deter immunological recognition
by the host.[20] Rupture and discharge of the infectious virus-packed
cells occur in the center of the lesion. MCV induces a benign
tumor instead of the usual necrotic pox lesion associated
with other poxviruses.[21]
Clinical manifestations
MCV produces a papular eruption of
multiple umbilicated lesions. The individual lesions are discrete,
smooth, and dome shaped. They are generally skin colored with
an opalescent character. The central depression or umbilication
contains a white, waxy curdlike core. The size of the papule
is variable, depending upon the stage of development, usually
averaging 2–6 mm. Papules may exceed 1 cm in size in
immunosuppressed hosts. The papules may become inflamed spontaneously
or after trauma and present atypically in size, shape, and
color. The lesions are often grouped in small areas but may
also become widely disseminated.
Any cutaneous surface may be involved,
but favored sites include the axillae, the antecubital and
popliteal fossae, and the crural folds. Rarely, MCV lesions
occur in the mouth or conjunctivae.[22,23,24] Autoinoculation
is common. Children usually acquire molluscum nonsexually
at both genital and nongenital areas. MCV in adults affects
the groin, genital area, thighs, and lower abdomen and is
often acquired sexually. Around 10% of cases develop an eczematous
dermatitis around the lesions, but this disappears as the
infection resolves.[25] Patients with atopic dermatitis can
have a disseminated eruption. Eruptions in immunocompromised
indiviuals are very resistant to treatment.[13,26]
Dermatopathology
Histologically, molluscum contagiosum
exhibits intraepidermal lobules with central cellular and
viral debris. In the basal layer, enlarged basophilic nuclei
and mitotic figures are seen. Progressing upward, the cells
show cytoplasmic vacuolization and then eosinophilic globules.
The nucleus becomes compressed at the level of the granular
cell layer, and the molluscum bodies lose their internal structural
markings. Undisrupted lesions show an absence of inflammation,
but dermal changes can include an infiltrate that is lymphohistiocytic,
neutrophilic, or granulomatous. The latter has been seen in
solitary lesions. Antibody to MCV by indirect immunofluorescence
has been found in 69% of patients with visible lesions.[27]
Polymerase chain reaction can detect MCV in skin lesions.[28]
Currently, there is no in-vitro or animal model for MCV. MCV
can undergo an abortive infection in some cell lines, which
can cause confusion with herpes simplex virus by laboratories.[29]
Two sets of investigators have infected human skin with molluscum
contagiosum and grafted it onto athymic mice, although there
was no continued viral replication.[30,31]
Diagnosis
The clinical appearance of molluscum
contagiosum is in most cases diagnostic. Though molluscum
cannot be cultured in the laboratory, histological examination
of a curetted or biopsied lesion can also aid in the diagnosis
in cases that are not clinically obvious. The thick white
central core can be expressed and smeared on a slide and left
unstained or stained with Geimsa, Gram, Wright, or Papanicolaou
stains to demononstrate the large brick-shaped inclusion bodies.
Electron microscopy has also been used to demonstrate the
poxivirus structures. Immunohistochemical methods using a
polyclonal antibody allows recognition of molluscum contagiosum
in fixed tissue.[32] In-situ hybridization for MCV DNA has
also been utilized.[33] Molluscum contagiosum lesions must
be differentiated from verruca vulgaris, condyloma accuminata,
varicella, herpes simplex, papillomas, epitheliomas, pyoderma,
cutaneuos cyptococcosis, epidermal inclusion cyst, basal cell
carcinoma, papular granuloma annulare, keratoacanthoma, lichen
planus, and syringoma or other adenexal tumors.
Treatment
Molluscum cantagiosum is a self-limited
disease, which, left untreated, will eventually resolve in
immunocompetent hosts but may be protracted in atopic and
immunocompromised individuals. Some patients pick and scratch
at the lesions, a habit that may lead to scarring. In addition,
some schools and daycare centers will not admit children with
visible molluscum papules. When patients seek medical attention
and desire to rid themselves of the papules, there are several
means of therapeutic destruction to help speed resolution.
The decision whether treatment is necessary depends on the
needs of the patient, the recalcitrance of their disease,
and the likelihood of treatments to leave pigmentary alteration
or scarring. Most of the common treatments consist of various
means to traumatize the lesions. Antiviral and immune-modulating
treatments have recently been added to the options. The following
is a brief summary of some of the more common treatments.
Cryosurgery
One of the most common, quick, efficient
methods of treatment is cryotherapy. Liquid nitrogen, dry
ice, or Frigiderm are applied to each individual lesion for
a few seconds. Repeat treatments in 2–3-week intervals
may be required.[34] Hyper- or hypopigmentation and scarring
may be caused by this treatment.
Evisceration
An easy method to remove the lesions
is eviscerating the core with an instrument such as a scalpel,
sharp tooth pick, edge of a glass slide, or any other instrument
capable of removing the umbilicated core. Because of its simplicity,
patients, parents, and caregivers may be taught this method
so new lesions can be treated at home.[35,36] This method
is simple but may not be tolerated by small children.
Curettage
Curettage is another method of removal.
It can be used with and without light electrodessication.
This method is more painful, and it is recommended that a
topical anesthetic cream be applied to the lesions before
the procedure to decrease the pain. This method has the advantage
of providing a reliable tissue sample to confirm the diagnosis.[35,37]
Tape stripping
Another reported treatment involves
the use of adhesive tape. The adhesive side of the tape is
repeatedly applied to and removed from the lesion for 10–20
cycles. This action effectively removes the superficial epidermis
from the top of the lesion.[38] However, repeated use of the
same strip has the potential to spread the virus to adjacent,
uninvolved skin.
Podophyllin and podofilox
A 25% suspension in a tincture of benzoin
or alcohol may be applied once a week. This treatment requires
some precautions. It contains two mutagens, quercetin and
kaempherol. Some of the listed side effects include severe
erosive damage in adjacent normal skin that may cause scarring
and systemic effects such as peripheral neuropathy, renal
damage, adynamic illeus, leucopenia, and thrombocytopenia,
especially if used generously on mucosal surfaces. Podofilox
is a safer alternative to podophyllin and may be used by the
patient at home. The recommended use usually consists of application
of 0.05 ml of 5% podofilox in lactate buffered ethanol twice
a day for 3 days.[35,38] The active agent is absolutely contraindicated
in pregnancy.
Cantharidin
Cantharidin (0.9% solution of collodian
and acetone) has been used with success in the treatment of
MCV. This blister-inducing agent is applied carefully and
sparingly to the dome of the lesion with or without occlusion
and left in place for at least 4 hours before being washed
off. Cantharidin can cause severe blistering. It should be
tested on individual lesions before treating large numbers
of lesions. It should not be used on the face. When tolerated,
this treatment is repeated every week until the lesions clear.
Usually 1–3 treatments are necessary.[39]
Tretinoin (Retin-A)
Tretinion 0.1% cream has been used
in the treatment of MCV. It is applied twice daily to the
lesions. Resolution was reported by day 11. Trace erythema
at the site of prior lesions was a noted side effect.[41]
Tretinion 0.05% cream has also been used with success and
decreased irritation.[35]
Cimetdine
Oral cimetidine has successfully been
used in extensive infections.[42] The histamine 2-receptor
antagonist stimulates delayed-type hypersensivity. One uncontrolled
study showed resolution in 9 of 13 patients. In this study,
the dosage was 40 mg/kg/day in two divided doses for 2 months.[43]
The authors recommended further placebo-controlled, double-blind
studies be completed to determine the efficacy of cimetidine
in treating MCV. Because cimetadine interacts with many systemic
medications, a review of the patient's other medications is
recommended.
Potassium hydroxide
Another treatment option is the use
of potassium hydroxide. In one study, an aqueous solution
of 10% KOH was applied topically twice daily to all lesions
with a swab. The treatment was discontinued when an inflammatory
response or superficial ulcer became evident. Resolution occurred
in a mean of 30 days.[44] This treatment had some complications
including hypertrophic scar formation and persistent or transitory
hyper- and hypopigmentation. A subsequent study in pediatric
patients recommended the use of 5% KOH and found it equally
effective with many fewer side effects.[45]
Pulsed dye laser
The use of pulsed dye laser for the
treatment of MC has also been documented with excellent results.
The therapy was well tolerated, without scars or pigment anomalies.
The lesions resolved without scarring at 2 weeks. Studies
show 96%–99% of the lesions resolved with one treatment.[46,47]
The pulsed dye laser is quick and efficient, but its expense
makes it less cost effective than other options.
Imiquimod (Aldara)
Imiquimod 5% cream has been used topically
to treat MCV by inducing high levels of IFN-a and other cytokines
locally.[48,49] This potent immunomodulatory agent is well
tolerated, although application site irritation is common.
It has had no known systemic or toxic effects in children.[50]
It is applied to the area nightly for 4 weeks. Clearing can
take up to 3 months.
Cidofovir
Cidofovir is a nucleoside analog that
has potent antiviral properties. Several small studies and
case reports describe the successful use of cidofovir applied
topically or administered by intralesional injection in several
virally induced cutaneous diseases.[51] Cidofovir cream 3%
has been used successfully to treat MCV in studies, with clearing
in 2–6 weeks.[52] Its high cost, need for extemporaneous
preparation, and carcinogenicity in some studies have limited
its use.[51]
Editorial Note: All
of the above treatments are invasive and potentially painful.
Discuss these options at length with your doctor before proceeding
if you choose to go with one of these methods. A report in
the journal Biomedicine and Pharmacotherapy, 2004 by Burke,
BE et al demonstrated good clearing of molluscum in children
treated with am extract of Australian essential oils. The
authors have improved upon the original work and an all natural,
painless treatment formula is available over-the-counter as
ZymaDerm.
Conclusion
Molluscum Contagiosum is a common,
generally benign, viral infection of the skin. It is common
in children, sexually active adults, and immunodeficient patients.
It is caused by the molluscipox virus, a member of the poxviridae
family. This virus differs from other poxviruses in that it
causes spontaneously regressing, umbilicated tumors of the
skin rather than poxlike vesicular lesions. In immunocompetent,
nonatopic patients molluscum contagiosum is usually a self-limited
disease for which treatment is not mandatory. However, when
treatment is deemed appropriate, multiple local therapeutic
options are available. For patients with impaired immune functions
with widespread and potentially disfiguring eruptions, the
usual local destructive therapies are ineffective; antiviral
and immunomodulatory medications have been more successful.
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Pediatr Dermatol 1999;16(5):414-415.© 2003 Dermatology
Online Journal
© 2003 Dermatology Online Journal
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