Molluscum contagiosum — SAQ

Stem

A 6-year-old boy presents with a 4-month history of multiple, asymptomatic, firm, pearly-white, dome-shaped papules with central umbilication scattered across the trunk and axillae. His mother is concerned because the lesions are multiplying and his school has asked whether he should be excluded. He is otherwise well, with no past medical history, no current medications, and no personal or family history of atopic dermatitis. On examination there are around 15 lesions, 2-4 mm in size, none inflamed, no surrounding eczema, no periocular lesions, and no regional lymphadenopathy.

Questions

a) State the most likely diagnosis and list three clinical features that support it. (2 marks)

• Diagnosis: Molluscum contagiosum.

^[1]

• Clinical features:
  1. Firm, pearly-white, dome-shaped papules with central umbilication.
  2. Multiple lesions on the trunk and axillae (typical paediatric distribution), sparing palms and soles.
  3. Asymptomatic, slow spread over months, with expression of a curd-like core from the umbilication (pathognomonic).

^[2][4]b) What is the causative organism and what is the histological hallmark? (2 marks)

• Causative organism: Molluscum contagiosum virus (MCV) — a large, double-stranded DNA poxvirus of the genus Molluscipoxvirus (family Poxviridae); MCV-1 is the predominant genotype in children and MCV-2 in HIV/immunocompromised hosts.
• Histological hallmark: cup-shaped epidermal down-growth containing large intracytoplasmic eosinophilic inclusions — the molluscum (Henderson- Patterson) bodies — that displace the nucleus in infected keratinocytes.

^[1][3]c) Outline your stepwise management plan for this immunocompetent child. (3 marks)

1. Reassurance and watchful waiting is first-line in an immunocompetent child with asymptomatic, non-facial, non-genital lesions — spontaneous resolution within 6-12 months (and almost always by 2 years) is the rule.
2. General measures: avoid sharing towels and sponges, cover the lesions where practical, discourage scratching to limit autoinoculation; the child does not need to be excluded from school (transmission is by close skin contact and fomites, not by airborne spread).
3. Active treatment is reserved for bothersome, spreading, facial, or genital lesions, or parental preference — and includes physical destructive methods (curettage, cryotherapy, cantharidin 0.7% topical solution / YCANTH — applied in clinic, washed off at 24 hours, producing a small blister; very effective in children) and topical agents (potassium hydroxide 5-10%, podophyllotoxin for genital lesions in adults, berdazimer sodium 10.3% gel / Zelsuvmi — a recently approved nitric-oxide-releasing topical). Imiquimod 5% is variably effective and largely superseded.

^[2]d) List three red-flag situations in molluscum contagiosum that warrant escalation, and the appropriate next step for each. (3 marks)

^[1]1. Extensive, giant (>1 cm), or refractory facial molluscum in an adult → test for HIV (and consider other immunocompromise); refer to dermatology; restore immune function (ART) as the cornerstone of therapy. 2. Genital molluscum in a child → safeguarding assessment (although autoinoculation from concurrent cutaneous lesions is the commonest cause, sexual abuse must be actively considered, especially in the absence of other lesions); involve paediatrics and child protection. 3. Periorbital molluscum with conjunctivitis, keratitis, or visual disturbance → urgent ophthalmology referral; keratoconjunctivitis from periocular molluscum is uncommon but sight-threatening if untreated.

References4ShowHide

1. [1]Hebert AA, Bhatia N, Del Rosso JQ. Molluscum Contagiosum: Epidemiology, Considerations, Treatment Options, and Therapeutic Gaps J Clin Aesthet Dermatol, 2023.PMID 37636018
2. [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. [3]Hebert AA, Bhatia N, Del Rosso JQ. Molluscum Contagiosum: Epidemiology, Considerations, Treatment Options, and Therapeutic Gaps J Clin Aesthet Dermatol, 2023.PMID 37636018
4. [4]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