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Q1: Definition and clinical presentation (2 min)
Candidate: Molluscum contagiosum is a common, self-limiting cutaneous infection caused by the molluscum contagiosum virus (MCV) of the Poxviridae family, transmitted by direct skin contact. The classic lesion is a firm, rounded, pink or skin-coloured papule with a shiny, umbilicated surface.[3]
Examiner: What does the central core contain, and what is its histological equivalent?
Candidate: The core contains molluscum bodies (Henderson-Patterson bodies) — intracytoplasmic inclusions in infected keratinocytes.[3]
Q2: Differential diagnosis (3 min)
Examiner: What are you distinguishing molluscum from, and how?
Candidate:
- Verruca vulgaris (common warts) — rough hyperkeratotic surface without central umbilication; common on hands and knees.
- Condyloma acuminatum (genital warts) — papillomatous surface, no umbilication.
- Closed comedones (acne) — small follicular papules with no umbilication.
- Milia — pinpoint pearly cysts with no umbilication, occurring on the face.
- Basal cell carcinoma — a solitary umbilicated papule in an adult needs biopsy to exclude BCC.
- In HIV: cryptococcosis, histoplasmosis and other deep fungal infections — all can produce umbilicated papules; biopsy if atypical.
- Folliculitis, sebaceous hyperplasia, syringoma, fibrous papule and lichen planus — distinguished on closer inspection and dermoscopy.
Examiner: And what is the characteristic dermoscopic sign?
Candidate: A white-yellow central area with peripheral crown vessels — characteristic of molluscum.[3]
Q3: Investigations (2 min)
Examiner: When is the diagnosis clinical, and when do you investigate?
Candidate: The diagnosis is clinical when the morphology and umbilication are typical; dermoscopy supports diagnosis without invasive testing. Skin biopsy is reserved for atypical lesions or where the diagnosis is uncertain.[3] In extensive adult disease, screen for immunosuppression including HIV.
[3]Q4: Management — stepwise approach (3 min)
Examiner: How do you decide between watchful waiting and active treatment, and what is your treatment ladder?
Candidate: In an immunocompetent child with asymptomatic lesions, watchful waiting is first-line — most cases are self-limited over months.[3] Active treatment is offered for bothersome, spreading, facial or genital lesions, parental preference, or immunocompromise.
Treatment ladder:
- Physical destructive: curettage; cryotherapy; topical cantharidin, routinely used for molluscum with efficacy and safety data in children.[1]
- Topical agents: potassium hydroxide, podophyllotoxin (genital disease in non-pregnant adults), imiquimod, and berdazimer 10.3% gel — a nitric-oxide-releasing agent with phase 3 trial evidence.[2]
- Intralesional immunotherapy for refractory disease — triggers a systemic immune response that clears both injected and distant lesions.
- General measures: avoid sharing towels, cover lesions, do not pick or scratch, screen for STIs in genital MC.[3]
[2]Examiner: How does management change in HIV?
Candidate: In HIV, management centres on immune reconstitution; disseminated or atypical lesions warrant a biopsy and opportunistic-infection workup.[3]
[1]Q5: Complications and prognosis (2 min)
Examiner: What complications and prognostic factors should a patient or parent know about?
Candidate:
- Complications: secondary bacterial infection, eczema-like reactions around the lesions, keratoconjunctivitis from periocular lesions, scarring, and psychosocial impact in extensive disease.[3]
- Prognosis: in immunocompetent children, self-resolution is the rule over months. In HIV, lesions are often refractory unless immune function is restored.[3]
- Red flags: extensive/giant/facial MC in an adult (HIV), genital MC in a child (safeguarding), periocular MC with eye symptoms (ophthalmology), and secondary bacterial infection.
References3ShowHide
- [1]Vakharia PP, Chopra R, Silverberg NB, et al. Efficacy and Safety of Topical Cantharidin Treatment for Molluscum Contagiosum and Warts: A Systematic Review Am J Clin Dermatol, 2018.PMID 30097988
- [2]Browning JC, Enloe C, Cartwright M, et al. Efficacy and Safety of Topical Nitric Oxide-Releasing Berdazimer Gel in Patients With Molluscum Contagiosum: A Phase 3 Randomized Clinical Trial JAMA Dermatol, 2022.PMID 35830173
- [3]Meza-Romero R, Navarrete-Dechent C, Downey C. Molluscum contagiosum: an update and review of new perspectives in etiology, diagnosis, and treatment Clin Cosmet Investig Dermatol, 2019.PMID 31239742