Pediatric Dermatology Consult - July 2016

Prognosis and treatment

Molluscum infections typically resolve spontaneously in months to years (average duration, 13 months),¹⁴ so treatment may not be required. The goal of treatment is to accelerate the resolution of the infection, but some studies have found that common treatments may not shorten the time to resolution.¹¹ However, if there is substantial pruritus, lesions are cosmetically undesirable, or a child has atopic dermatitis and is at increased risk for autoinoculation, treatment may be warranted.¹⁵ Furthermore, molluscum lesions can scar, so prevention of autoinoculation may help minimize scarring.¹⁶

Few high-quality studies of the efficacy of molluscum treatments exist, and a 2009 Cochrane review found insufficient evidence to recommend any therapy for molluscum. The most common treatment used by pediatric dermatologists is cantharidin,¹⁷ and this treatment also is available to primary care practitioners. This option is preferred over other destructive methods such as curettage or liquid nitrogen cryotherapy because it is not painful or traumatic and is well tolerated by pediatric patients.⁸ Parent and physician satisfaction with the therapy is high; 78%-95% of parents would use cantharidin treatment again for molluscum recurrence.^4,8,18 Originally extracted from the blister beetle but now synthesized commercially,¹⁹ cantharidin causes vesiculation at the dermoepidermal junction6 by destroying intercellular connections.4 Vesiculation of the skin causes extrusion of the molluscum body, which facilitates resolution of the lesion.¹⁹ The cantharidin formulation is applied directly to molluscum lesions with the wooden end of a cotton-tipped applicator.⁴ Patients may be directed to wash it off after 4-6 hours. Blistering is an expected, desired outcome. A minority of patients may experience mild temporary pain (7%), more significant blistering (2.5%), burning (less than 1%), pruritus (less than 1%), or irritation (less than 1%).⁴ There is a risk of scarring and pigmentary changes, but these risks also exist for untreated lesions.¹⁹ Cantharidin treatment is repeated approximately every 4 weeks, and 90% of cases resolve after an average of 2.1 treatments.¹⁸ Topical retinoids can be used in an attempt to trigger an irritant response by the immune system, and they are the preferred therapy for facial lesions, but they are inconsistently effective.4 Randomized controlled trials found that imiquimod, a previously popular treatment is not effective,²⁰ and the evidence for cimetidine is contradictory.^21,22 Molluscum dermatitis and id reaction can be treated with medium strength topical steroids. 

References

1. Viral diseases of the skin, in "Hurwitz Clinical Pediatric Dermatology," 4 ed. (New York: Elsevier, 2011, pp. 348-69). .
2. Molluscum, in "Red Book Report of the Committee on Infectious Diseases," 2015.

Ms. Haddock is a medical student at the University of California, San Diego, and a research associate at Rady Children's Hospital-San Diego. Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children's Hospital-San Diego and professor of dermatology and pediatrics at the University of California, San Diego. Dr. Eichenfield and Ms. Haddock state they have no relevant financial disclosures.