A 6-year-old girl has been seen by at least three providers, each of whom offered a different diagnosis for the dermatologic changes to her arm (staph infection, warts, and dermatitis). None of the prescribed treatments for these conditions—a 10-day course of cephalexin; salicylic acid; and hydrocortisone cream, respectively—have resolved the problem. Therefore, her mother brings the child to dermatology.

Further questioning reveals a marked history of atopy, characterized by seasonal allergies, occasional hives, and asthma. Both parents experienced these same problems as children.

Examination reveals a 5-cm ill-defined collection of firm 2- to 4-mm papules covering the bilateral antecubital areas. These are superimposed on a background of slightly erythematous, slightly scaly skin. A total of three angry-looking pustules are interspersed among the smaller shiny, firm papules.

ANSWER
The correct answer is test treatment with liquid nitrogen (choice “c”), which would elicit the pathognomic umbilication seen in most molluscum papules. Cultures for bacteria or viruses (choice “a” or “b”) would not help, since this is not a bacterial condition and since the poxvirus is difficult to grow in culture. Punch or shave biopsy (choice “d”) would establish the diagnosis and is occasionally necessary, but it is not called for in this case.

DISCUSSION
This combination of molluscum papules, which occasionally become inflamed and pustular, and underlying eczematous changes is quite common. It has been called “eczematized molluscum.”

The antecubital distribution and personal and family history of atopy should put the provider on notice immediately. The diagnosis usually can be made on empiric grounds, without the diagnostic liquid nitrogen or biopsy. But when in doubt, confirmation is quick and easy.

The majority of molluscum patients will be atopic or will have parents or siblings who are. Patients with atopy are notoriously susceptible to skin infections, especially from viral organisms.

Most children with molluscum will acquire immunity within a few months, with or without treatment. But it is arguably sensible to treat a few lesions with topical preparations such as cantharidin, a blistering agent that destroys the treated lesions and may prompt the immune system to destroy the rest.

As with molluscum’s cousin, the wart, many different treatments for removing the papules have been tried, including destructive modalities such as liquid nitrogen. All have drawbacks, such as pain and blistering.

With this combination of atopy and warts or molluscum, a healthy dose of patient (or, more importantly, parent!) education is essential before treatment is attempted, since parents of these patients are often confused and worried. Parents and providers are often frightened by the occasional red, pustular molluscum. However, only rarely does this represent secondary bacterial infection.