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Molluscum Contagiosum

BASICS

Description

  • Common, benign, contagious viral skin infection caused by a poxvirus
  • Small (2–5 mm), waxy white/flesh-colored, dome-shaped papules with central umbilication
  • Self-limited in immunocompetent; disfiguring in immunocompromised
  • Spread: autoinoculation, contact, shared items, sexual transmission

EPIDEMIOLOGY

  • Prevalence: 1% in U.S., mostly children (2–15 y) and sexually active adults
  • Occurs in 5–18% of people with HIV

ETIOLOGY & PATHOPHYSIOLOGY

  • DNA virus from Poxviridae family; 4 types (clinically indistinguishable)
  • Cytoplasmic replication, induces abnormal epithelial proliferation
  • Incubation: 2–6 weeks
  • Resolution: 6–24 months
  • No malignancy, no reactivation by other poxviruses

RISK FACTORS

  • Skin-to-skin contact, contact sports, swimming
  • Atopic dermatitis, sexual activity
  • Immunosuppression: HIV, chemo, steroids, biologics

PREVENTION

  • Avoid direct contact, shared items, and sexual activity during outbreaks

ASSOCIATED CONDITIONS

  • Atopic dermatitis, immunosuppressive medications, HIV/AIDS

DIAGNOSIS

History

  • Contact, sports, sexual activity

Physical Exam

  • Discrete, firm, umbilicated papules, 2–5 mm (may be >1 cm in immunocompromised)
  • Curd-like core, pearly/flesh/red color
  • Sites: intertriginous areas, anogenital, conjunctiva
  • Consider immunodeficiency if fever, >50 lesions, poor response
  • Pediatric red flags: <3 months (check for vertical transmission); anogenital lesions (rule out abuse)

Differential Diagnosis

  • Warts, varicella, milia, BCC, condyloma, folliculitis, keratoacanthoma, trichoepithelioma, etc.

DIAGNOSTIC TESTS

Initial Tests

  • Virus cannot be cultured
  • Scrape lesion: Henderson-Patterson bodies
  • KOH prep or H&E stain for confirmation
  • STI testing (if sexually acquired)

Dermatoscopy

  • Central pore, polylobular white-yellow core, crown vessels

TREATMENT

General Measures

  • Observation preferred in healthy patients
  • No FDA-approved treatment; approach depends on age, site, # lesions, comorbidities

First-Line

  • Cantharidin 0.7–0.9%: office application, covered and washed off in 2–6 hrs
  • Repeat q2–4 weeks
  • Avoid face/genitals
  • AE: blistering, pain, erythema, pruritus

Second-Line

  • Benzoyl peroxide 10%: BID x 4 weeks
  • Imiquimod 5%: 3–5×/week × 12 weeks (not first-line; AE: mucositis, vitiligo)
  • Other topicals: podophyllotoxin, TCA, SA, GA, tretinoin
  • Cimetidine (PO): 25–40 mg/kg/day
  • Cidofovir (topical/IV) in refractory HIV

REFERRAL

  • Immunocompromised or non-responders to 1st- and 2nd-line therapy

SURGERY/PROCEDURES

  • Cryotherapy: 1–2 cycles, repeat q3–4 weeks
  • AE: pain, edema, erythema

  • Contra: cryoglobulinemia, Raynaud’s

  • Curettage: under local/topical anesthesia

  • AE: pain, scarring

  • Intralesional immunotherapy:

  • Antigens: Candida, PPD, MMR, vitamin D
  • AE: erythema, allergic rxn, anaphylaxis

COMPLEMENTARY & ALTERNATIVE

  • Lemon myrtle oil 10%: daily × 21 days
  • KOH 5–10%: 1–2× daily until resolution

PEDIATRIC CONSIDERATIONS

  • Treatment optional in immunocompetent
  • Pain: topical lidocaine/EMLA (risk: methemoglobinemia)

PREGNANCY

  • Safe treatments: curettage, cryotherapy, incision, expression

ONGOING CARE

Follow-Up

  • Varies with treatment type

Patient Education

  • Cover lesions, avoid scratching
  • No sharing towels/clothes
  • Avoid sex during active lesions

PROGNOSIS

  • Immunocompetent: self-resolves in 3–12 months (up to 4 years)
  • Immunocompromised: persistent, difficult to treat

COMPLICATIONS

  • Secondary infection
  • Scarring, hyper-/hypopigmentation (mainly due to treatment)

ICD-10

  • B08.1 – Molluscum contagiosum

Clinical Pearls

  • Observation is often best in healthy individuals
  • Lesions resolve naturally without scarring
  • No treatment proven superior or FDA-approved
  • Consider topical steroids for associated dermatitis or pruritus