Diagnostic Considerations
The cutaneous manifestations of other opportunistic infections, such as cutaneous cryptococcosis, histoplasmosis, and aspergillosis, may mimic molluscum contagiosum and must be ruled out in immunocompromised hosts. (See the images below.)
This lesion of cutaneous coccidioidomycosis could be included among the differential diagnoses of molluscum contagiosum.
This keratoacanthoma could be included among the differential diagnoses of molluscum contagiosum.
Molluscum contagiosum may be randomly associated with other lesions, such as epidermal cysts, nevocellular nevi, sebaceous hyperplasias, and Kaposi sarcoma. Pseudocystic molluscum contagiosum, giant molluscum contagiosum, and molluscum contagiosum associated with other lesions are responsible for frequent clinical misdiagnoses.
Infection of children through sexual abuse is possible; however, to a greater extent than warts, molluscum contagiosum virus is quite common on the genital, perineal, and surrounding skin of children. [20, 21] Regard abuse as unlikely, unless other suspicious features are present.
Histologic or microscopic confirmation of molluscum contagiosum is indicated in patients who are immunocompromised because several life-threatening opportunistic infections may clinically mimic molluscum contagiosum.
Conditions to consider in the differential diagnosis of molluscum contagiosum include the following:
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Keratoacanthoma
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Verruca vulgaris (warts)
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Eccrine poroma
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Epidermal cyst
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Foreign body granuloma
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Lichen planus
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Flat warts (verruca plana)
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Pyoderma
Perforating disorders (all very rare in children) to consider in the differential diagnosis of molluscum contagiosum include the following:
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Acquired reactive perforating dermatosis of renal failure
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Kyrle disease
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Perforating serpiginous elastoma
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Perforating folliculitis
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Verrucous perforating collagenoma
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Perforating granuloma annulare
Differential diagnoses to consider in patients with AIDS include the following:
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Cutaneous cryptococcus [22] : Cutaneous cryptococcus presents as molluscumlike eruptions (on the face, it often has a very dramatic appearance); the patient may have few or no other symptoms associated with cryptococcal meningitis.
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Cutaneous coccidioidomycosis
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Cutaneous histoplasmosis
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Cutaneous aspergillosis
Differential Diagnoses
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Note the central umbilication in these classic lesions of molluscum contagiosum.
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Molluscum contagiosum. Approximately 10% of patients develop eczema around lesions. Eczema associated with molluscum lesions spontaneously subsides following removal.
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Molluscum contagiosum on the shaft of the penis. Molluscum contagiosum in the genital region of adults is most commonly acquired as a sexually transmitted disease.
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Molluscum contagiosum. Larger lesions may have several clumps of molluscum bodies rather than the more common single central umbilication. This may make them difficult to recognize as molluscum contagiosum.
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Molluscum lesions may become quite numerous in intertriginous areas. This child has autoinoculated lesions to both inner thighs.
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After trauma, or spontaneously after several months, inflammatory changes result in suppuration, crusting and eventual resolution of the lesion. This inflammatory stage does not usually represent secondary infection and seldom requires antibiotic therapy.
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Lesions of molluscum contagiosum have a characteristic histopathology. Lobules containing hyalinized molluscum bodies, also known as Henderson-Paterson bodies, are diagnostic.
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This lesion of cutaneous coccidioidomycosis could be included among the differential diagnoses of molluscum contagiosum.
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This keratoacanthoma could be included among the differential diagnoses of molluscum contagiosum.
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Molluscum contagiosum. Lesions on the upper eyelid of a 3-year-old child.
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In a patient who had preexisting molluscum contagiosum, the virus was inoculated along a line of minor skin trauma, resulting in the development of the 3 new lesions.
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Molluscum contagiosum on the right axilla.
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Presented here are the classic umbilicated papules of molluscum contagiosum lesions on the cheek of a child. Facial lesions occur frequently in children, although lesions generally are few.
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Molluscum contagiosum rarely occurs on the face in an adult unless the patient is infected with HIV. When molluscum contagiosum occurs in individuals infected with HIV, facial lesions are common and frequently numerous.
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Molluscum contagiosum lesions in individuals infected with HIV may number in the hundreds. In addition, they may become quite large and prominent.
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This low-power view of a molluscum contagiosum lesion shows the classic cup-shaped invagination of the epidermis into dermis. The Henderson-Paterson bodies are identified readily and stained purple to red in this image.
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This is a medium-power view of a molluscum contagiosum lesion. Magnification allows better demonstration of the intracytoplasmic molluscum bodies (staining purple-pink) within the keratinocytes.
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This molluscum contagiosum body is an intracytoplasmic inclusion body. Notice in the image that the keratinocyte nuclei are displaced to the periphery of the cell and that the intracytoplasmic inclusions have a granular quality.
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Multiple papules on the face of a man with HIV.
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Cytoplasmic viral inclusions become progressively larger toward the epidermal surface (hematoxylin and eosin, 200X)
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Low-power histopathologic examination reveals an overall cup-shaped appearance.
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Viral particles have a dumbbell-shaped appearance. Courtesy of Alvin Zelickson, MD.
