Molluscum infection is a benign epidermal eruption of the skin, caused by Molluscum contagiosum, a DNA virus. 

Molluscum infection occurs in these settings: 

• Routine physical contact or occasionally fomites usually affecting children. Affect face and neck, trunk, or limbs. 

• Sexual transmission usually affecting young adults.  Affects genitals, pubic region, lower abdomen, upper thighs, and/or buttocks.  

• Severe molluscum infection in the context of immunocompromise, notably late-stage HIV.

Immunocompetent

• Molluscum lesions are usually characteristic, presenting as smooth-surfaced, firm, dome-shaped papules with central umbilication. Their colour can vary from pearly white or pink to yellow. Lesions are usually 2–5 mm diameter.  
• Can affect almost any part of the body, rarely the oral cavity or sole of the foot. 
• Are frequently asymptomatic, though occasionally associated with itch, discomfort or secondary bacterial infection.
• Will usually regress spontaneously within months leaving no sequelae.

Immunocompromised

• Molluscum infection in immunocompromised states can be significantly more aggressive and widespread, presenting with 100 or more lesions in one individual and progressing as confluent, coalescing plaques. Can be large (giant mollusca).
• Extensive disease usually occurs in the setting of late HIV, with CD4 counts significantly under 200 and concurrent illnesses related to advanced HIV infection.

Diagnosis is predominantly clinical, on the basis of recognising the characteristic lesions.

General advice

• Patients must be warned of risks of autoinoculation and advised against shaving or waxing their genital regions, to prevent further spread of lesions. 
• Towels, bed linen, clothes etc. should not be shared when active lesions are present, to reduce risk of onward transmission.
• Lesions should be covered prior to using swimming pools.
• Genital molluscum - offer a routine STI screen.

Recommended treatment

• Expectant management (no treatment). This recommendation is guided by a Cochrane review of molluscum treatments at nongenital sites (I, A.)
• Some treatments may shorten the disease course
• No one treatment is advocated over another,  choice is influenced by a number of factors, including comparative efficacy, side effects, cost and ease of use.
• If patients opt for treatment, they must be informed that new lesions can appear for a while, necessitating more than one treatment course.
  • Podophyllotoxin 0.5%.  Applied twice daily for three consecutive days, with a pause for four days. It can be repeated after a week if necessary, for four weeks. Local reaction can occur. (Ib, A.)
  • Imiquimod 5% cream (unlicensed for this purpose).  Applied three times weekly and washed off 6–10 h later, for up to 16 weeks. (Ib, A.) Local reaction can occur.
  • Liquid nitrogen therapy (IV, C.). Common side effects include pain, inflammation and oedema at treated areas. Pigment change, hair loss and superficial scarring are rare.

Alternative treatment

• Curettage, light emitting and pulsed dye lasers are unsuitable for routine use in the genital area. (Level IV, C.)  
• Chemical preparations are not recommended for use. (Level IV, C.)

Pregnancy and breastfeeding 

• Cryotherapy and other destructive methods are safe. Podophyllotoxin and imiquimod should be avoided.

Immunocompromised patients

• Molluscum infection can be particularly difficult to treat in late-stage HIV using conventional mean though usually responding to HIV antiretroviral treatment (ARV) initiation (Level IV, C). 
• Topical cidofovir has demonstrated some efficacy in the treatment of non-genital recalcitrant molluscum infection in the setting of HIV immunosuppression. However, its use is frequently associated with significant local inflammation and therefore cannot be recommended for use on genital skin. (Level IV C.)
• An immune reconstitution inflammatory syndrome (IRIS) reaction to molluscum may occur when starting ARVs.