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Dermatology Quiz and Case Discussion

From The Child's Doctor, Fall 2006

Anthony J. Mancini, MD
Head, Dermatology, Ann & Robert H. Lurie Children's Hospital of Chicago; Professor of Pediatrics and Dermatology, Northwestern University Feinberg School of Medicine
Disclosure: Dr. Mancini has no industry relationships to disclose. He refers to cantharidin, podophyllin, podophylotoxin, salicylic acid, phenol, potassium hydroxide, topical retinoids, silver nitrate, trichloroacetic acid, intralesional interferon, oral cimetidine, imiquimod cream, and cidofovir. These products are not labeled for use in discussion, but are well documented in the literature for this use.
Leslie P. Lawley, MD
Fellow, Dermatology, Children's Memorial Hospital
Disclosure: Dr. Lawley has no industry relationships to disclose. She refers to cantharidin, podophyllin, podophylotoxin, salicylic acid, phenol, potassium hydroxide, topical retinoids, silver nitrate, trichloroacetic acid, intralesional interferon, oral cimetidine, imiquimod cream, and cidofovir. These products are not labeled for use in discussion, but are well documented in the literature for this use.

Other Disclosure Information

Educational objectives

At the conclusion of this activity, participants will be able to:

  • Recognize the lesions shown in the photographs and described in the vignettes
  • Discuss differential diagnosis
  • Describe appropriate treatment

CME credit

Credit statement

1. An otherwise-healthy 8-year-old boy presents for evaluation of multiple papules on his arms, legs (Figure 1) and trunk. He has developed over 50 of these lesions, which are asymptomatic, over the last 4-5 months.

The most likely etiology is:

A. Herpes simplex virus

B. Poxvirus

C. Varicella zoster virus

D. Human papilloma virus

E. Enterovirus

2. A 2-year-old girl presents with similar skin lesions on her trunk and extremities, which have been present for 8 months. Her mother reports that over the last 2 weeks, many of these previously flesh-colored papules have become acutely red (Figure 2) and increased in size. There is no pain, tenderness or discharge, and she has had no fever or other symptoms.

The most appropriate therapeutic approach to this patient is:

A. Topical corticosteroid ointment

B. Systemic antibiotic therapy

C. Reassurance and watchful waiting

D. Skin culture and topical antibiotic therapy

E. Manual curettage

3. A 7-year-old female is referred for evaluation of an itchy rash. It has been present for 6 weeks, involves the arms, trunk and legs (Figure 3), and was preceded by several flesh-colored papules in the same distribution.

The appropriate treatment is:

A. Topical corticosteroid ointment followed by a return visit for treatment of the papules

B. Topical imiquimod cream and cryotherapy

C. Reassurance and watchful waiting

D. Skin culture and topical antibiotic therapy

E. Oral cimetidine at high-dose for 8 weeks


Answers: 1B, 2C, 3A



Molluscum contagiosum is a common infection of the skin seen most often in school-aged children, and caused by the molluscum contagiosum virus (MCV), a poxvirus. In a recent US study two-thirds of patients were less than 8 years old.[1] In adults, molluscum contagiosum is often associated with sexual transmission and/or immunodeficiency. These associations are rare in children, in whom MCV is likely spread through innocent skin-to-skin contact. A relationship between swimming pool exposure and development of molluscum contagiosum has been suggested.[2,3] Four different genotypes of MCV have been isolated; infection with MCV type 1 results in the majority of pediatric cases of molluscum contagiosum.[4]

Clinically, flesh-colored, pearly dome-shaped papules are observed upon examination. A central area of umbilication may or may not be present. Molluscum lesions may occur anywhere on the body, but are most often seen on the trunk in patients less than 5 years of age and on the extremities in those over 5 years of age.[1] The antecubital and popliteal fossae, axillae, and groin are common sites of involvement, and autoinoculation is frequently noted in these areas, felt to be secondary to skin-to-skin contact. Occasionally, an associated dermatitis surrounding a group of molluscum lesions is present, and has been termed “molluscum dermatitis.” The resultant scratching in these areas may propagate autoinoculation, with the development of additional lesions.[5] Even though MCV is typically not associated with immunodeficiency in children, it may take 18 to 24 months for the host immune system to react against the virus. Once this occurs, individual lesions often become acutely erythematous and edematous, a clinical sign heralding spontaneous resolution, which is usually complete within 2 to 3 weeks.

Molluscum contagiosum is typically diagnosed on a clinical basis. If there is a question, curette of an individual lesion may be performed, and the contents smeared onto a glass slide. Microscopic evaluation following application of an appropriate stain (Wright, Gram, Giemsa or Papanicolaou) will reveal viral inclusion (also known as Henderson-Patterson) bodies.[6] Skin biopsy is rarely indicated, but will also reveal the characteristic viral inclusions on hematoxylin and eosin-stained sections.

The differential diagnosis of molluscum contagiosum may be broad, and can include herpes simplex infection, verruca vulgaris, syringoma (and other adnexal tumors), pyoderma, papular granuloma annulare, condyloma acuminatum, cutaneous Cryptococcus infection, histoplasmosis, keratoacanthoma, epidermal inclusion cyst, basal cell carcinoma, neurilemmoma, or pyogenic granuloma.[6] The lesions of herpes simplex infection are vesicular and painful, and cluster on an erythematous base. Verruca vulgaris (common wart) presents with hyperkeratosis and verrucous surface changes, and lack central umbilication. Condylomata acuminata (anogenital warts) may be difficult to distinguish, but usually show some verrucous changes and also lack central umbilication. Pyoderma usually presents with erythema, crusting and purulent discharge. Adnexal tumors, keratoacanthoma, and basal cell carcinoma are very rare in children, and may occasionally mimic the flesh-colored popular nature of molluscum. These lesions, along with those of papular granuloma annulare and neurilemmoma, can be easily differentiated on histologic evaluation. Pyogenic granuloma presents as a vascular papule, which is often accompanied by surface erosion, compressibility, and a history of bleeding. Cutaneous cryptococcosis and histoplasmosis usually occur in the setting of immunodeficiency.

While treatment of molluscum is not necessary, many parents are concerned about the appearance, contagiousness, or associated symptoms (ie, itching in the presence of molluscum dermatitis), and request intervention.[2] Since the natural history is one of eventual spontaneous resolution, treatment for these lesions should be as painless as possible and entail no increased risk of scarring. Therapeutic options are multiple, and have included cantharidin (Asian blister beetle extract), podophyllin, podophylotoxin, curettage, cryotherapy, salicylic acid, phenol, potassium hydroxide, topical retinoids, silver nitrate, trichloroacetic acid, intralesional interferon, oral cimetidine, tape stripping, manual core extraction, electrodessication, carbon dioxide laser, pulsed dye laser, imiquimod, and cidofovir.[7,8] The success of most of these therapies is varied and inconsistent.

Cantharidin is an extremely safe, effective and well-tolerated treatment when applied sparingly (with the blunt end of a wooden applicator stick) to non-facial, non-fold area lesions.[9] It does result in minor blistering, and mild discomfort may occur in the first 24 hours following treatment. Up to 30 lesions are treated in 1 visit, with repeat visits scheduled at 3 to 8 week intervals as necessary. Parents must be thoroughly educated in rinsing the treated areas (usually in 4 hours) and in expecting blistering prior to healing. When an associated molluscum dermatitis is present, it should be treated with a topical corticosteroid cream or ointment in an attempt to alleviate itching and help prevent autoinoculation and secondary bacterial infection.[10]

Facial lesions pose a therapeutic challenge, as cantharidin is not safe for use in this setting. The strategies most often employed for facial lesions include watchful waiting, topical retinoids, imiquimod cream, or light cryotherapy (in patients who can tolerate this treatment). Surgical removal or curettage is occasionally necessary for larger eyelid lesions.


[1.] Dohil MA, et al. The epidemiology of molluscum contagiosum in children. J Am Acad Dermatol 2006;54(1):47-54.

[2.] Braue A, et al. Epidemiology and impact of childhood molluscum contagiosum: A case series and critical review of the literature. Pediatr Dermatol 2005;22(4):287-294.

[3.] Choong KY, Roberts LJ. Molluscum contagiosum, swimming and bathing: A clinical analysis. Australas J Dermatol 1999;40(2):89-92.

[4.] Gottlieb SL, Myskowski PL. Molluscum contagiosum. Int J Dermatol 1994;33(7):453-461.

[5.] Paller AS, Mancini AJ. Hurwitz Clinical Pediatric Dermatology. 3rd ed. Philidelphia: Sanders; 2006:412-415.

[6.] Tyring S. Mucocutaneous Manifestations of Viral Disease. New York: Marcel Dekkor Inc; 2002:59-65.

[7.] Bolognia J, Jorizzo JL, Rapini RP. eds. Dermatology. Edinburgh: Mosby; 2003:1266-1267.

[8.] Leslie KS, Dootson G, Sterling JC. Topical salicylic acid gel as a treatment for molluscum contagiosum in children. J Dermatolog Treat 2005;16(5-6):336-340.

[9.] Silverberg NB, Sidbury R, Mancini AJ. Childhood molluscum contagiosum: Experience with cantharidin therapy in 300 patients. J Am Acad Dermatol 2000;43(3):503-507.

[10.] Brown J, et al. Childhood molluscum contagiosum. Int J Dermatol 2006;45(2):93-99.

Accreditation Statement

The Northwestern University Feinberg School of Medicine is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

Credit Designation Statement

The Northwestern University Feinberg School of Medicine designates this live activity for a maximum of 2 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.