Differentiating Plantar Warts from Corns
The definitive diagnostic test is paring down the lesion with a scalpel after soaking in warm water: pinpoint bleeding from exposed capillary loops is pathognomonic for a plantar wart, whereas a translucent central core without bleeding indicates a corn, and homogeneous thickened keratin without bleeding indicates a callus. 1, 2
Clinical Differentiation Features
Plantar Warts
- Appearance: Hyperkeratotic papulonodules with disrupted or absent skin lines (dermatoglyphics) across the lesion 1
- Location: Can occur anywhere on the sole, not necessarily at pressure points 1
- Paring test: Reveals pinpoint bleeding from thrombosed capillaries within elongated dermal papillae—this is pathognomonic 1, 2, 3
- Pain pattern: Often described as painful but not specifically related to pressure 1
- Causative agent: Human papillomavirus (HPV types 1,2,4,27,57) 1
Corns (Heloma Durum)
- Appearance: Hard, yellow lesions with a central nucleus or plug of keratin 2
- Location: Occur at pressure points—typically on tips of toes or underneath metatarsal heads on weight-bearing surfaces 2
- Paring test: Reveals a translucent central core without bleeding 1, 2
- Pain pattern: Pain described as "walking on a small stone or pebble" 2
- Skin lines: Preserved, unlike warts 1
Calluses
- Appearance: Diffuse, yellowish thickening at pressure areas 1
- Paring test: Shows homogeneous thickened keratin without bleeding 1
- Pain: Generally less painful than corns 2
- Distribution: Broader, more diffuse than corns 2
Diagnostic Algorithm
- Soak the lesion in warm water to soften tissue 1
- Pare down carefully with a scalpel blade, removing superficial layers 1
- Inspect closely for:
- Assess skin lines: Disrupted lines favor wart; preserved lines favor corn or callus 1, 2
Red-Flag Features Requiring Biopsy
- Lesions that fail to respond to standard wart therapy 1
- Atypical symptoms such as pruritus 1
- Pigmented and enlarging lesions 1
- Occurrence in immunosuppressed patients 1
- Unusually severe or prolonged warts 1
First-Line Treatments
For Plantar Warts
Salicylic acid 15-40% topical paints or ointments applied daily after paring is the first-line treatment (Level of evidence 1+, Strength A). 1, 4
- Apply to pared wart surface daily 1
- Alternative: Cryotherapy with liquid nitrogen applied fortnightly for 3-4 months 1
- Important caveat: Expectant management is entirely acceptable for immunocompetent patients with asymptomatic warts, as 50% clear spontaneously within 1 year in children and two-thirds by 2 years 1
- Recurrence occurs in at least 25% of cases within 3 months with all treatment modalities 1
For Corns
Aggressive mechanical debridement by a podiatrist is first-line treatment, combined with pressure redistribution and cushioning. 2
- Professional blade or scalpel debridement 2
- Keratolytics such as urea 10% cream applied three times daily 2
- Pressure redistribution with properly fitting footwear that accommodates foot shape 2
- Cushioning to prevent recurrence 2
For Calluses
- Manual debridement or paring 2
- Self-management using emery boards or nail files after softening the skin 2
- Urea-based creams applied daily to weekly depending on thickness 2
- Pressure redistribution and cushioning 2
Critical Pitfalls to Avoid
- Never use chemical corn removers or plasters on diabetic patients due to high complication risk 2
- Avoid overdebridement of any lesion, which can cause pain and tissue damage 1
- Do not use destructive treatments on facial warts without extreme caution due to scarring risk 1
- Recognize that wart treatments do not eradicate HPV infection—the virus can remain infectious outside the body for months or years 1
- In immunosuppressed patients (organ transplant recipients, HIV-positive individuals), maintain a lower threshold for biopsy as these patients have elevated risk of HPV-associated squamous cell carcinoma 1