Question
Molluscum contagiosum
Answer
Molluscum contagiosum is a common, benign, self-limiting cutaneous viral infection caused by Molluscum Contagiosum Virus (MCV), a large, double-stranded DNA virus belonging to the Poxviridae family (genus Molluscipoxvirus).
Transmission: direct skin-to-skin contact, autoinoculation (spread by scratching), fomites (shared towels/clothing), and, in adults, sexual contact when lesions are genital/perigenital — the mode/pattern of transmission and typical patient age group differ (children — usually non-sexual close contact; sexually active adults — genital lesions via sexual contact; immunocompromised individuals — can develop more extensive, atypical disease).
Clinical features: characteristic small, firm, dome-shaped, pearly/flesh-coloured papules with a pathognomonic central umbilication (dimpling) — usually multiple, a few millimetres in diameter, generally asymptomatic (occasionally mildly pruritic), most common on the trunk, extremities, and (in sexually transmitted cases) the genital/perianal region; in immunocompromised patients (particularly advanced HIV/AIDS), lesions can be unusually numerous, large, and widespread (“giant molluscum”), sometimes serving as a clinical clue prompting HIV testing.
Laboratory diagnosis: usually a clinical diagnosis based on the characteristic appearance; if confirmation is needed, microscopic examination of material expressed from a lesion (or histopathology of a biopsy) shows characteristic large, eosinophilic intracytoplasmic inclusion bodies (Henderson-Patterson bodies or “molluscum bodies”) within infected epidermal keratinocytes.
Natural course and treatment: typically self-limiting in immunocompetent individuals, resolving spontaneously over months (up to 6–12 months or occasionally longer) without treatment, though treatment is often pursued for cosmetic reasons, to reduce autoinoculation/spread, or due to persistent lesions — options include physical destruction (curettage, cryotherapy) or topical agents (e.g., podophyllotoxin, cantharidin); in immunocompromised patients, lesions can be more extensive and persistent, sometimes requiring more aggressive management alongside addressing the underlying immunosuppression.