• Molluscum contagiosum is a clinical diagnosis. The appearance of lesion(s) allows other conditions to be excluded (for example warts). Lesions do not usually cause symptoms, unless they become inflamed or develop an eczematous reaction. Diagnostic investigations are not necessary.
• Typically, the person presents with lesions which have developed over a few weeks:
• Lesions are pinkish or pearly white papules with a central umbilication, and are up to 5 mm in diameter. For images, see www.dermis.net.
• Lesions appear in clusters in areas anywhere on the body (except the palms of the hands and the soles of the feet):
• In children, lesions are commonly seen on the trunk and in flexures, but anogenital lesions may also occur.
• In adults, sexual contact may lead to lesions developing on the genitalia, pubis, thighs, and lower abdomen.
• Rarely, lesions can occur on the oral mucosa and on the eyelids.
• Immunocompromised people (e.g. with HIV) or people on immunosuppressants (e.g. corticosteroids) can present with atypical lesions (e.g. larger, more widespread, and numerous [possibly up to 100] lesions).

• The differential diagnosis of molluscum contagiosum includes [Smolinski and Yan, 2005; BASHH, 2008]:
• Warts — often have a rough surface, with no central umbilication. See the CKS topics on Warts - anogenital and Warts and verrucae.
• Milia — white keratinous cysts on the face, most frequently around the eyes.
• Lichen planus (uncommon) — an inflammatory pruritic disease characterized by distinctive, usually purplish, papules.
• Syringomata (uncommon) — small pale papules, usually around the eyes.
• Cutaneous cryptococcosis — umbilicated papules; not uncommon on the face, found in people with immunosuppression (especially HIV).
• Up to a third of children may have symptoms or rashes complicating the diagnosis of molluscum contagiosum [Jones and Kress, 2007].
• Inflammation around lesions normally occurs prior to resolution, and is a normal immune response [Lowy, 1999]. It is important to differentiate inflammation from eczema or a bacterial skin infection, both of which may require treatment [Nelson and Morrell, 2007].

These recommendations are based on pragmatism and expert opinion from a review article [Highet, 1992; Nelson and Morrell, 2007].

• The differential diagnosis of molluscum contagiosum includes [Smolinski and Yan, 2005; BASHH, 2008]:
• Warts — often have a rough surface, with no central umbilication. See the CKS topics on Warts - anogenital and Warts and verrucae.
• Milia — white keratinous cysts on the face, most frequently around the eyes.
• Lichen planus (uncommon) — an inflammatory pruritic disease characterized by distinctive, usually purplish, papules.
• Syringomata (uncommon) — small pale papules, usually around the eyes.
• Cutaneous cryptococcosis — umbilicated papules; not uncommon on the face, found in people with immunosuppression (especially HIV).
• Up to a third of children may have symptoms or rashes complicating the diagnosis of molluscum contagiosum [Jones and Kress, 2007].
• Inflammation around lesions normally occurs prior to resolution, and is a normal immune response [Lowy, 1999]. It is important to differentiate inflammation from eczema or a bacterial skin infection, both of which may require treatment [Nelson and Morrell, 2007].