by Kristy Fleming, MD
Two months ago, an otherwise healthy 24-year-old man developed asymptomatic lesions on his groin. He is an avid bicyclist and attributed the lesions to irritation from the friction of his bicycle seat and clothing. The patient was seen by his primary-care clinician two weeks prior and was placed on oral clindamycin (Cleocin) and cephalexin (Keflex). No improvement was noted with the antibiotic treatment, and the patient became concerned when he noticed the lesions were increasing in number. He is sexually active but reported no history of sexually transmitted infection.What’s your diagnosis? Submit your answer, and then read the full explanation below. If you like this activity or have a suggestion, tell us about it in the comment box at the bottom of the page.
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Molluscum contagiosum is a very common benign and self-limited cutaneous viral infection in children that can also occur in adults. In children, molluscum presents as one to hundreds of lesions on the face, trunk and/or extremities.1 Genital lesions are seen in 10% of generalized childhood cases, but those confined to the genital area warrant an investigation for sexual abuse.2
In adults, molluscum contagiosum cases are mostly sexually transmitted infections or associated with immunodeficiency, especially HIV infection.
Molluscum contagiosum is generally spread through skin-to-skin contact, and immunocompetent adults typically present with lesions in the genital region. There are usually fewer than 20 lesions that favor the lower abdomen, upper thighs and penile shaft.1 Mucosal involvement is very rare.2 Transmission through fomites has been reported, and the virus may also be spread in water from bathtubs and swimming pools.3 Additionally, koebnerization can also result in molluscum contagiosum lesions that appear as solitary papules, cluster or linear configurations.
Molluscum contagiosum lesions present as 2 to 5 mm dome-shaped umbilicated papules, ranging in color from flesh tone to slightly pearly or translucent.1,2 Immunocompromised hosts may experience “giant” lesions that are up to 1.5 cm in size, which can be cosmetically disfiguring.2
Excrescences are occasionally observed protruding from the central dell.1 Dermatitis surrounding the lesions is common and can sometimes be misdiagnosed as eczema if no primary lesions are observed.
Inflammation of molluscum contagiosum papules signifies a host immune response and often heralds impending resolution.3
Clinicians who regularly see children are likely well versed in identifying and diagnosing molluscum contagiosum, but practitioners with a patient population limited to adults may not have a high index of suspicion for this diagnosis.
The differential diagnosis of papules in the groin of an adult is broad and includes appendageal tumors, verrucae, condyloma acuminata and papular granuloma annulare. In immunocompromised patients, the possibility of opportunistic infections must also be considered.3
Fortunately, the characteristic molluscum contagiosum histologic appearance is easy to identify. Lesions demonstrate large, bright purple to magenta-colored intracytoplasmic inclusion bodies (molluscum bodies or Henderson-Patterson bodies), in epidermal keratinocytes.3
Clinicians should offer adult patient with molluscum contagiosum evaluation for additional sexually transmitted infections.
Molluscum contagiosum lesions will spontaneously resolve, but complete resolution may take a number of years. Patients often seek medical treatment if the lesions are pruritic or cosmetically bothersome, or if they fear transmitting the infection to others.
Treatment modalities commonly employed include curettage, cryotherapy and in-office cantharidin application. Case reports indicate that other therapies, such as imiquimod cream, topical tretinoin cream, topical keratolytics, tape application, pulsed dye laser, topical cidofovir and oral cimetidine may also be effective.1,3 Clinicians should counsel patients to practice safe sex.
1. Paller AS, Mancini AJ. Hurwitz Clinical Pediatric Dermatology, 3rd Ed. Elsevier; 2006:412-415.
2. James WD, Berger TG, Elston DM. Andrew’s Diseases of the Skin Clinical Dermatology,10th ed. Saunders Elsevier; 2006: 394-397.
3. Bolognia J, Jorizzo JL, Rapini RP. Dermatology, 2nd Ed. Elsevier; 2008: 1232-1233.