What is the differential diagnosis (Ddx) for facial lesions suspected to be molluscum contagiosum in an elderly adult?

Differential Diagnosis for Facial Molluscum in an Elderly Adult

In an elderly adult with facial lesions resembling molluscum contagiosum, the primary concern is distinguishing true molluscum from basal cell carcinoma, keratoacanthoma, and cryptococcal infection, with the presence of multiple large lesions strongly suggesting an underlying immunocompromised state that requires immediate investigation. 1, 2

Key Differential Diagnoses to Consider

Malignant Conditions (Highest Priority)

• Basal cell carcinoma is a critical differential for facial lesions in elderly patients, as giant molluscum can mimic this malignancy with similar dome-shaped appearance and pearly surface 3
• Keratoacanthoma presents as rapidly growing nodules that can be confused with atypical molluscum lesions, particularly when umbilication is not clearly visible 3

Infectious Etiologies

• Cryptococcal infection must be considered in any elderly patient with umbilicated papules resembling molluscum, especially if immunocompromised, as cryptococcosis can present with identical-appearing lesions in HIV patients 4, 3
• Atypical mycobacterial infection can mimic molluscum with nodular facial lesions 3
• Cutaneous histoplasmosis may present similarly in immunosuppressed individuals 3

Other Benign Conditions

• Intradermal nevi can appear as flesh-colored papules on the face 3
• Viral warts may be confused with molluscum, though typically lack the characteristic shiny surface and central umbilication 3
• Pyogenic granuloma should be considered if lesions show prominent vascular features 3

Critical Clinical Assessment Points

Features Suggesting True Molluscum

• Characteristic appearance: skin-colored, whitish, or pink papules with shiny surface and central umbilication 1, 2
• Early lesions may appear as simple dome-shaped papules without visible umbilication, requiring careful examination 1
• Associated conjunctivitis if lesions are on or near eyelids, with mild to severe follicular reaction 5, 4

Red Flags for Immunocompromised State

• Multiple large lesions (>5 mm) with minimal inflammation strongly indicate immunodeficiency and warrant immediate HIV testing and evaluation for other causes of immunosuppression 1, 2, 3
• Atypical presentations including giant, disseminated, necrotic, polypoidal, or nodular forms suggest severe immunocompromise 1
• Extensive disease that is recalcitrant to standard treatment 2

Diagnostic Algorithm

Initial Assessment

• Examine for classic umbilication and shiny, dome-shaped appearance, noting that early or inflamed lesions may lack typical features 1
• Assess distribution and number of lesions, as multiple large facial lesions in an elderly adult are atypical for immunocompetent molluscum 1, 2
• Check for periocular involvement and associated conjunctivitis 5, 4

When Diagnosis is Uncertain

• Dermoscopy should be performed to look for central orifice and characteristic vascular patterns (punctiform, radial, or mixed flower pattern) 6, 7
• For giant lesions (>5 mm), dermoscopy may show yellowish globules of different sizes with polymorphic vessels 3
• Biopsy is mandatory if diagnostic uncertainty persists, particularly to exclude basal cell carcinoma or cryptococcal infection 1, 8, 3

Immunodeficiency Screening

• Order HIV testing if multiple large lesions with minimal inflammation are present 1, 2
• Consider other causes of immunosuppression including hematologic malignancies, immunosuppressive medications, and organ transplantation 3
• Refer to dermatology for examination of other suspicious lesions and management of extensive disease 1

Common Pitfalls to Avoid

• Do not assume all umbilicated facial papules in elderly patients are benign molluscum without considering malignancy, especially basal cell carcinoma 3
• Do not overlook the possibility of cryptococcal infection in patients with risk factors for immunosuppression, as this requires systemic antifungal therapy 1, 4
• Do not delay biopsy when the clinical presentation is atypical or when lesions are large (>5 mm), as this may represent either malignancy or severe immunodeficiency 8, 3
• Do not treat empirically without confirming diagnosis in elderly patients, as the differential is broader and more serious than in children 3