Clinical Description of Warts
Warts are benign epidermal growths caused by human papillomavirus (HPV) infection of keratinocytes, presenting as hyperkeratotic lesions with characteristic pinpoint bleeding when pared down, revealing exposed capillary loops of elongated dermal papillae 1.
Pathophysiology
Warts develop through HPV infection at the basal layer of the epidermis, leading to clonal proliferation, epidermal thickening, and hyperkeratinization. The visible wart appears weeks to months after initial infection 1. Over 150 HPV genotypes exist, with specific types causing different wart morphologies 1.
Common Clinical Types
1. Common Wart (Verruca Vulgaris)
- Appearance: Dome-shaped, hyperkeratotic papulonodules
- Location: Most frequently on hands, arms, legs, and periungual regions 2, 3
- HPV types: Predominantly types 1,2,4,27, or 57 1
- Size: Typically 0-2 cm, though giant variants can occur 2, 4
2. Plantar Wart (Verruca Plantaris)
- Appearance: Hyperkeratotic lesions over pressure points
- Location: Heel or metatarsal heads of feet 3
- Distinguishing feature: Must be differentiated from corns and calluses through paring and close inspection 1
- Special variant: Myrmecia warts (deep palmoplantar warts caused by HPV-1) show characteristic large intracytoplasmic inclusion bodies histologically 5
3. Flat/Plane Wart (Verruca Plana)
- Appearance: Flat, slightly elevated lesions
- Location: Commonly on dorsum of hands or face 3
- HPV types: Types 3 or 10 1
- Differential: Must be distinguished from lichen planus or thin seborrhoeic keratoses 1
4. Genital Wart (Condyloma Acuminatum)
- HPV types: Low-risk types 6 and 11 (most common at 45.7% and 22.86% respectively), high-risk types 16,18,31,33,35,39,45,51,52,56,58,59 4, 6
- Clinical significance: In immunocompromised patients (e.g., men with HIV), 25% may have high-grade squamous intraepithelial lesions requiring screening 6
Key Diagnostic Features
The pathognomonic sign is pinpoint bleeding when the lesion is pared down, exposing capillary loops of elongated dermal papillae 1. This distinguishes warts from:
- Actinic keratoses
- Knuckle pads
- Squamous cell carcinoma
- Focal palmoplantar keratoderma
- Corns and calluses (on feet)
Clinical Course and Epidemiology
- Prevalence: 5-30% of children and young adults 1
- Transmission: Direct skin-to-skin contact or contaminated surfaces; broken/cut skin is more susceptible 7
- Natural history in children: 50% clear at 1 year, two-thirds by 2 years 1
- Natural history in adults: Much slower clearance; persistence for 5-10 years is not uncommon 1
Important Clinical Pitfalls
Immunocompromised Patients
Warts may be large, extensive, and resistant to treatment 1. Unusually severe or prolonged warts should prompt consideration of:
- Lymphoma
- Idiopathic CD4 lymphocytopenia
- HIV infection
- Organ transplant recipients 1
Malignant Potential
In epidermodysplasia verruciformis (EV) and long-term immunosuppressed individuals, certain HPV types (beta-papillomaviruses) carry increased risk of progression to squamous cell carcinoma 1. Chronic, giant, isolated lesions—particularly periungual—can be misdiagnosed and require biopsy verification 2.
Morphological Variations
HPV-1 can produce varied clinical appearances depending on anatomical location, including common wart morphology, digitate warts, cutaneous horns, or even herpes-like appearances on healing burn scars 8. Do not rely solely on morphology for diagnosis when the presentation is atypical.
Clinical Appearance Summary by Location
- Hands/fingers: Dome-shaped, periungual common warts
- Feet: Plantar warts over pressure points; may have central depression
- Face: Flat warts; require cosmetically acceptable treatment approaches
- Anogenital region: Condyloma acuminatum; screen for high-grade dysplasia in immunocompromised patients