Diagnosis of Molluscum Contagiosum
Molluscum contagiosum is diagnosed clinically by identifying characteristic skin-colored, whitish, or pink papules (2-5 mm) with a shiny surface and central umbilication, typically distributed on the trunk, face, and extremities in children. 1, 2
Primary Clinical Features
The diagnosis relies on recognizing the pathognomonic appearance:
- Papule characteristics: Dome-shaped, smooth-surfaced, pearly, firm papules measuring 2-5 mm in diameter with central umbilication that develops as lesions mature 1, 3
- Color variations: Skin-colored, pink, whitish, or yellow papules with a shiny surface 1, 2
- Distribution pattern: Most commonly affects trunk, face, and extremities in children and adolescents 1, 2
Key Diagnostic Considerations
Early or Atypical Presentations
Early lesions may appear as simple dome-shaped papules without central umbilication, requiring careful examination for shiny, dome-shaped papules even when the classic umbilication is absent. 1
When umbilication is not visible, look for:
- Shiny, dome-shaped papules in characteristic distribution 1
- Associated findings such as perilesional eczema or inflammatory reactions 1
- Conjunctivitis if lesions are located on or near the eyelids 1, 2
Dermoscopy as Diagnostic Aid
Dermoscopy reveals characteristic features that can confirm the diagnosis:
- Yellowish-white polylobulated structures with peripheral telangiectasia 4
- Central yellow globule with white structureless area and irregular linear vessels at the periphery in smaller lesions 5
- Multiple shiny white clods in some cases 5
Red Flags for Immunocompromised State
Multiple large lesions (>5 mm, termed "giant molluscum") with minimal inflammation should prompt screening for immunodeficiency, particularly HIV. 1, 5
In immunocompromised patients, atypical manifestations include:
- Giant lesions (>5 mm in diameter) 5
- Disseminated, necrotic, polypoidal, or nodular forms 1, 4
- Pseudocysts or abscesses 1, 4
- Minimal inflammation despite extensive disease 1
Important differential diagnosis: Cryptococcal infection can present with umbilicated papules resembling molluscum contagiosum in HIV patients and should be considered when presentations are atypical. 6, 1
Associated Findings to Assess
Examine for complications that may require specific management:
- Conjunctivitis: Present when lesions are on or near eyelids, ranging from mild to severe with follicular reaction 1, 2
- Perilesional eczema: Common inflammatory manifestation around lesions 1, 4
- Bacterial superinfection: Occasional complication presenting with pain, redness, or purulent drainage 2, 7
- Inflammatory reactions: May include BOTE sign, Gianotti-Crosti syndrome-like reaction, ID reaction, erythema annulare centrifugum, or erythema multiforme 4
When to Pursue Further Evaluation
Biopsy or dermoscopy with dermatology referral is recommended when:
- Atypical presentations occur, particularly in immunocompromised patients 1
- Diagnostic uncertainty exists 1
- Extensive or recalcitrant disease is present 1
- Giant lesions or unusual morphology raises concern for alternative diagnoses (basal cell carcinoma, keratoacanthoma, cryptococcosis, histoplasmosis) 5
Clinical Course Information
Understanding the natural history aids diagnosis:
- Lesions typically persist 6-12 months but can last up to 4-5 years without treatment 1, 2, 8
- Transmission occurs through direct skin contact, fomites, or self-inoculation 1
- In immunocompromised patients, lesions persist longer and may be more extensive 2, 5
Common pitfall: Failing to identify nascent (early) lesions during initial examination, as these lack the characteristic umbilication but remain infectious and can lead to continued autoinoculation. 1