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Molluscum contagiosum: an evidence-based review.

Molluscum contagiosum (MC) is a highly infectious poxvirus that infects the skin and, rarely, the mucous membranes. (1) The estimated incidence of MC in the United States has not been well studied, but a study from the Netherlands showed that 17% of children and teenagers less than 15 years of age had the infection. (2) MC is seen in a bimodal distribution, with most cases occurring in childhood, followed by a sharp drop in incidence during adolescence, then a sharp rise in young adulthood. (3)

Transmission of Infection

Transmission is usually by direct contact--young children sharing a bath, youngsters roughhousing in swimming pools, and contact sports such as wrestling are typical examples. Infection with the MC virus can also occur through fomites, such as shared towels, and by autoinoculation, especially when an individual with pruritic MC lesions (molluscum dermatitis) scratches the skin. (1) In young adulthood, MC infection often is sexually transmitted. (1)

Predisposing Diseases and Drugs

A number of diseases predispose patients to developing larger numbers of MC and a more severe infection. Two of the most common are atopic dermatitis (4) and Darier's disease. (5)

Patients who are immunosuppressed, including those who have received organ transplants (5) or have leukemia, (6) comprise another population at increased risk for more severe cases of MC. Patients with human immunodeficiency virus (HIV) infection are also at greater risk. In fact, the prevalence of MC infection is also higher in this latter group: an estimated 5% to 18% of patients infected with HIV develop MC. (7)

In a paper published in 1971, topical corticosteroids were implicated as agents that increase the risk for MC infection. (8) However, the association was quite tenuous, and those results have never been confirmed. Some clinicians also believe--erroneously--that the same association exists between MC and finmunomodulators. In fact, anecdotally, many clinicians have found that treatment of molluscum dermatitis with either a topical corticosteroid or an immunomodulator makes MC infection itself more amenable to treatment as a result of restoration of normal skin barrier function.

Natural History and Reason to Treat

MC is a benign, self-limited infection. All lesions spontaneously clear within 2 to 4 years. (9) However, this does not mean that patients with MC should not be treated.

With proper treatment, complications may be avoided. These include bleeding, the development of secondary infection such as impetigo, and the development of molluscum dermatitis, which is associated with itching and discomfort. (1) As noted above, scratching can cause lesion spread by autoinoculation. When MC lesions develop around the eyes, chronic keratoconjunctivitis is a potential complication. (10)

In addition, the number of MC lesions that develop usually is associated with the duration of the infection. (1) Treatment that shortens the course of MC infection is likely to reduce the number of lesions a patient might otherwise develop. Brown and colleagues (11) reported that treatment can shorten the course of the disease to about 6 to 8 months (down considerably from about 2 to 4 years). An estimated 7% of untreated lesions resolve with some degree of scarring, (1) so a patient with a long-standing infection may develop a large number of scars. (12) MC lesions also may cause or exacerbate an eczematous rash. (13)

Finally, and not least, MC lesions on exposed areas of the skin--and, particularly, on the face--subject a patient to psychosocial consequences, (10) including embarrassment and social exclusion because of fear of contagion.

Diagnosis

MC lesions (Figure 1) typically appear as smooth, dome-shaped papules 1 to 2 mm in diameter. Often, these will have an erythematous base. Central umbilication is the classic sign of MC but usually is clearly seen only in larger lesions. In early lesions, umbilication may not be readily apparent but may be visible with magnification (with dermoscopy, for example). (14)

The trunk, axillae, antecubital and popliteal fossae, and crural folds are the most common anatomic sites for development of lesions, but they may appear anywhere on the body. When MC occurs in the perianal area, the lesions must be distinguished from condylomata acuminata. Lesions around the eyes may be confused with benign appendageal tumors, including chalazion. Giant molluscum--lesions >2 cm in diameter--may resemble deep fungal infections such as cryptococcosis and histoplasmosis.

When MC lesions are characteristic in appearance and are found in the common anatomic locations, the diagnosis can be made based on those clinical findings. To confirm the clinical diagnosis, a Tzanck preparation can be made of a scraping from the central core of an umbilicated lesion. If present, molluscum bodies--the largest viral body seen in dermatology practice--will be clearly identifiable on microscopic examination. If lesions are not characteristic and/or are in uncommon anatomic locations and if a Tzanck preparation fails to demonstrate molluscum bodies, a biopsy may be indicated.

[FIGURE 1 OMITTED]

Treatment Options

A number of treatments for MC have been discussed in the literature, and 10 of these strategies will be reviewed briefly here (Table). It should be noted that, to date, no treatment currently available for MC is approved for this indication by the US Food and Drug Administration.

Watchful waiting certainly is an option. This strategy costs very little, and no office visits are required. However, the potential consequences of not actively treating MC--as discussed above--make watchful waiting an undesirable choice for most patients.

Curettage is undoubtedly an effective treatment for MC. In a case series of 110 children, Kakourou and colleagues (15) demonstrated 100% clearance of lesions with three treatments. However, despite its efficacy, curettage is associated with local bleeding and pain, (1) distinct disadvantages in young patients and in patients of any age who have more than just a few lesions.

Cryotherapy is an effective and acceptable therapy, especially on the face, in older children with a small number of lesions. However, it is uncomfortable and may not be tolerated by younger children. (16,17)

Cantharidin is a treatment that is both effective and painless when applied appropriately and carefully. In a study conducted at Children's Memorial Hospital in Chicago, (18) 90% of 300 patients experienced clearing, 8% improved, only 2% had no response. Cantharidin is painless on application and causes an asymptomatic blister. However, the compound is caustic and is not suitable for home application. It must be applied by a clinician, and so this modality requires office visits. Also, the only lesions that clear are the ones to which cantharidin is applied.

The sites of cantharidin application should be chosen carefully. The trunk and extremities are good locations for treatment, but the face, neck, and any intertriginous areas are not because of the risk that cantharidin will spread beyond the center of the treated lesions and cause blistering of noninfected skin.

Imiquimod 5% cream as monotherapy for molluscum has yielded promising results in some studies. In a study of 15 patients, (19) 8 (53%) achieved complete clearance of lesions using imiquimod once daily five times per week. Four other patients (27%) had a 50% reduction in lesions. In the subset of children in the study (n = 7), six (86%) had complete regression of lesions. In a placebo-controlled study by Theos and colleagues, (20) 33% of patients had complete clearance and 67% had partial response (vs 9% and 18%, respectively, in the control group)--a large, though not statistically significant, difference.

Because of imiquimod's mechanism of action, which induces local immune responses, local inflammation is an expected reaction. Usually, the resulting erythema is mild and well tolerated. In the study by Hengge and colleagues, (19) almost one third of patients reported erythema, although only one patient withdrew from the study. As a result of its mechanism of action, imiquimod stimulates dendritic cells to produce interferon alpha. Although it is well documented that systemic administration of interferons can cause side effects such as malaise and fever, topical administration of imiquimod has rarely been associated with such side effects. The most recently reported association was a case report of fever in a child treated with imiquimod. (21)

Tretinoin cream has been mentioned as potentially useful for treating MC, (1,22) although no controlled efficacy and safety trials have been done. Nevertheless, tretinoin may be helpful, particularly for treating areas of the body that are cosmetically sensitive--such as the face--where cantharidin use may not be advisable.

[FIGURE 2 OMITTED]

Pulsed dye laser also has been discussed in the literature as an effective therapy for ME. (23,24) However, this modality is costly, unlikely to be covered by health insurance plans, and, because it can cause some discomfort, may require the use of general anesthesia when being used in pediatric patients. However, pulsed dye laser is dramatically effective for MC, resulting in 100% clearance and no permanent scarring, so it is an option for children with multiple lesions who do not respond to other therapies.

Salicylic acid gel, 12%, was reported as 87% effective within 6 months (that is, complete clearance) in one placebo-controlled trial, (25) although this dramatic result must be considered in relation to the results in the control group: 60% of patients who used vehicle only also had complete clearance. This compound is available over the counter, is reasonably effective, and is well tolerated. However, clearance of lesions may require many months of use.

Cimetidine has been studied in a limited way in MC, and the results of these clinical trials are equivocal. In one of these studies, 2 months of treatment with high-dose cimetidine yielded clearance of lesions In 10 of 13 patients (77%). (26) However, other studies have been published showing that cimetidine, used either for MC or for warts, is not effective. (27)

Combination therapy with cantharidin plus imiquimod was shown to be effective in a series of 16 pediatric patients with MC. (28) The investigators applied cantharidin once in the office, then had patients apply imiquimod 5% cream daily for 5 weeks. According to the published study, 75% of patients had at least 90% clearance of MC lesions. These results are encouraging and deserve further study.

Conclusion

A number of treatment strategies have been tried in MC, several with good success and others with varying degrees of limited utility, either because of lack of efficacy or because of other disadvantages, including side effects, high cost, or the need for long duration of treatment. The choice of modality should be age-appropriate; the other main factors to consider are the number of lesions present and their anatomic location. Several of the modalities discussed in particular, pulsed dye laser and cimetidine--should be reserved for cases in which other therapies have failed.

Acknowledgement

Special thanks to Shay Jones, PA-C, MEd, MPH, for his valuable assistance in the development and writing of this article.

References

(1.) Brown J, Janniger CK, Schwartz RA, Silverberg NB. Childhood molluscum contagiosum. Int J Dermatol. 2006;45:93-99.

(2.) Koning S, Bruijnzeels MA, van Suijlekom-Smit LW, van der Wouden JC. Molluscum contagiosum in Dutch general practice. Br J Gen Pract. 1994;44:417-419.

(3.) Dohil MA, Lin P, Lee J, Lucky AW, Paller AS, Eichenfield LF. The epidemiology of molluscum contagiosum in children. J Am Acad Dermatol. 2006;54:47-54.

(4.) Keipert JA. The association of molluscum contagiosum and infantile eczema. Med J Aust. 1971;1:267-270.

(5.) Euvrard S, Kanitakis J, Cochat P, Cambazard F, Claudy A. Skin diseases in children with organ transplants. J Am Acad Dermatol. 2001;44:932-939.

(6.) Cotton DWK, Cooper C, Barrett DF, Leppard BJ. Severe atypical molluscum contagiosum infection in an immunocompromised host. Br J Dermatol. 1987;116:871-876.

(7.) Schwartz JJ, Myskowski PL. Molluscum contagiosum in patients with human immunodeficiency virus infection. A review of twenty-seven patients. J Am Acad Dermatol. 1992;27:583-588.

(8.) Hellier FF. Profuse mollusca contagiosa of the face induced by corticosteroids. Br J Dermatol. 1971;85:398.

(9.) Sturt RJ, Muller HK, Francis GD. Molluscum contagiosum in villages of the West Sepik District of New Guinea. Med J Aust. 1971;2:751-754.

(10.) Redmond RM. Molluscum contagiosum is not always benign. BMJ. 2004;329:403.

(11.) Brown J, Janniger CK, Schwartz RA, Silverberg NB. Childhood molluscum contagiosum. Int J Dermatol. 2006;45:93-99.

(12.) Weller R, O'Callaghan CJ, MacSween RM, White MI. Scarring in molluscum contagiosum: Comparison of physical expression and phenol ablation. BMJ. 1999;319:1540.

(13.) Laughter D, Istvan JA, Tofte SJ, Hanifin JM. The prevalence of atopic dermatitis in Oregon schoolchildren. J Am Acad Dermatol. 2000;43:649-655.

(14.) Zaballos P, Ara M, Puig S, Malvehy J. Dermoscopy of molluscum contagiosum: A useful tool for clinical diagnosis in adulthood. J Eur Acad Dermatol Venereol. 2006;20:482-483.

(15.) Kakourou T, Zachariades A, Anastasiou T, Architectonidou E, Georgala S, Theodoridou M. Molluscum contagiosum in Greek children: A case series. Int J Dermatol. 2005;44:221-223.

(16.) White MI, Weller R, Diack P. Molluscum contagiosum in children--evidence based treatment. Clin Exp Dermatol. 1997;22:51.

(17.) Kuflik EG. Cryosurgery updated. J Am Acad Dermatol. 1994;31: 925-944.

(18.) Silverberg NB, Sidbury R, Mancini AJ. Childhood molluscum contagiosum: Experience with cantharidin therapy in 300 patients. J Am Acad Dermatol. 2000;43:503-507.

(19.) Hengge UR, Esser S, Schultewolter T, et al. Self-administered topical 5% imiquimod for the treatment of common warts and molluscum contagiosum. Br J Dermatol. 2000;143:1026-1031.

(20.) Theos AU, Cummins R, Silverberg NB, Paller AS. Effectiveness of imiquimod cream 5% for treating childhood molluscum contagiosum in a double-blind, randomized pilot trial. Cutis. 2004;74:134138,141-142.

(21.) Campanelli A, Krischer J, Saurat JH. Topical application of imiquimod and associated fever in children. J Am Acad Dermatol. 2005;52:E1.

(22.) Thomas JR III, Doyle JA. The therapeutic uses of topical vitamin A acid. J Am Acad Dermatol. 1981;4:505-513.

(23.) Hughes PS. Treatment of molluscum contagiosum with the 585nm pulsed dye laser. Dermatol Surg. 1998;24:229-230.

(24.) Hancox JG, Jackson J, McCagh S. Treatment of molluscum contagiosum with the pulsed dye laser over a 28-month period. Curls. 2003;71:414-416.

(25.) Leslie KS, Dootson G, Sterling JC. Topical salicylic acid gel as a treatment for molluscum contagiosum in children. J Dermatolog Treat. 2005;16:336-340.

(26.) Dohil M, Prendiville JS. Treatment of molluscum contagiosum with oral cimetidine: Clinical experience in 13 patients. Pediatr Dermatol. 1996;13:310-312.

(27.) Cunningham BB, Paller AS, Garzon M. Inefficacy of oral cimetidine for nonatopic children with molluscum contagiosum. Pediatr Dermatol. 1998;15:71-72.

(28.) Ross GL, Orchard DC. Combination topical treatment of molluscum contagiosum with cantharidin and imiquimod 5% in children: A case series of 16 patients. Australas J Dermatol. 2004;45:100-102.

DOUGLAS W. KRESS, MD
TABLE. Treatment Options for
Molluscum Contagiosum

* Watchful waiting
* Curettage (1,15)
* Cryotherapy (16,17)
* Cantharadin (18)
* Imiquimod 5% cream (19-21)
* Tretinoin cream (1,22)
* Pulsed dye laser (23,24)
* Salicylic acid gel, 12% (25)
* Cimetidine (26,27)
* Combination therapy:
cantharidin + imiquimod (28)
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Author:Kress, Douglas W.
Publication:Family Practice News
Article Type:Disease/Disorder overview
Geographic Code:1USA
Date:Jul 1, 2007
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