Differentials
Warts
SIGNS / SYMPTOMS
All warts have abnormal skin markings or dermatoglyphics. Verrucous papules and plaques typify most warts, the sole being the most common location. Some warts are filiform coming to a point, and on the genitalia, condyloma are usually flat plaques.
INVESTIGATIONS
Paring warts reveals pinpoint bleeding. Biopsy specimens demonstrate verrucous hyperkeratotic skin lesions as opposed to Henderson-Patterson bodies seen in molluscum.
Immunoperoxidase staining or in situ polymerase chain reaction (PCR) can be done to identify human papillomavirus subtypes, which are the molecular confirmation techniques for warts.
Deep fungal infection (Cryptococcosis and Penicillium marneffei)
SIGNS / SYMPTOMS
Patients with Cryptococcosis and Penicillium marneffei infection are very ill, usually immunosuppressed, with fever and systemic symptoms including central nervous system changes.
INVESTIGATIONS
Fungal smears, cultures and latex agglutination tests from lesions, spinal taps, and blood will demonstrate fungal elements. A skin biopsy stained with fungal stains will demonstrate spores.
Herpes simplex virus
SIGNS / SYMPTOMS
Molluscum contagiosum can develop on an erythematous background, and can be incorrectly diagnosed as herpes simplex or herpes zoster.
INVESTIGATIONS
A viral swab will detect herpes infection.
Milia
SIGNS / SYMPTOMS
While these lesions are small papules with central orifices, they tend to be smaller than, and not as pearly as, molluscum. Milia typically occur over the cheeks, whereas molluscum is seen in the axilla or groin more commonly.
INVESTIGATIONS
Biopsy can differentiate these two, but as both conditions are benign, it is rarely needed.
Lichen nitidus (lichen planus)
SIGNS / SYMPTOMS
Lichen nitidus presents with small papules involving the flexor aspects of the forearms, backs of hands, the penis, chest, abdomen, and buttocks.
INVESTIGATIONS
Biopsy can differentiate between molluscum infection and other inflammatory dermatoses.
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