Differentiating and Treating Calluses, Corns, and Warts
Diagnostic Approach
The key diagnostic maneuver is paring down the lesion with a scalpel—warts will show pinpoint bleeding from exposed capillary loops, while corns and calluses will not. 1
Clinical Differentiation
Warts (Verrucae):
- Paring reveals pinpoint bleeding as capillary loops of elongated dermal papillae are exposed 1
- Dermoscopy shows homogenous black/red dots in 100% of cases (both pared and unpared) 2
- Caused by HPV infection (types 1,2,4,27, or 57 for plantar warts) 1
- Disrupt normal skin lines
- May have a rough, cauliflower-like surface
Corns (Clavi):
- Translucent central core visible on dermoscopy (present in 92.85% unpared, 100% pared lesions) 2
- Focal, circumscribed hyperkeratotic lesion with a hard conical core pointing toward bone 3
- Develop at pressure points where insufficient soft tissue exists between skin and bone 4
- Pain results from the conical core pressing on underlying structures 4
- No bleeding with paring
Calluses (Tylomas):
- Homogenous opacity on dermoscopy (75% unpared, 100% pared cases) 2
- Diffuse thickening without a central core 3
- Develop from persistent continuous or intermittent pressure 4
- Generally less painful than corns
- No bleeding with paring
Dermoscopy Enhancement
Dermoscopy significantly improves diagnostic accuracy and can distinguish these lesions without paring 2. This non-invasive tool allows visualization of morphological features invisible to the naked eye and can also monitor treatment response 5.
Treatment Algorithms
For Warts:
First-line: Salicylic acid (10-26%) with or without lactic acid (Level of evidence 1+, Strength of recommendation A) 1
Treatment protocol:
- Abrade or pare down lesions before application
- Soak the area prior to treatment
- Apply carefully to avoid surrounding normal skin (which may spread infection)
- Consider occlusion for enhanced efficacy 1
- Warts are 16 times more likely to clear with SA than placebo 1
Alternative: Cryotherapy as a physical destructive method 1
Important caveat: In immunocompetent patients with asymptomatic warts, watchful waiting is entirely acceptable 1. In children, 50% clear spontaneously at 1 year and two-thirds by 2 years. However, adult warts may persist 5-10 years 1.
Red flag: Unusually severe or prolonged warts should prompt evaluation for underlying immunodeficiency (lymphoma, HIV, idiopathic CD4 lymphocytopenia) 1
For Corns and Calluses:
Primary treatment: Address the underlying mechanical cause 6, 4
- Properly fitting footwear
- Pressure relief with corn/callus pads 6
- Address foot deformities (most common underlying cause) 4
Conservative debridement: Gentle paring to reduce hyperkeratotic tissue
Surgical excision: Reserved for intractable cases
- Can be performed with primary closure, skin flap, or healing by secondary intention 3
- Important pitfall: Surgical treatment has recurrence rates as high as conservative therapy, and resulting scars may cause similar complaints 4
- Consider combination with bony surgery if structural abnormality present 3
Common Diagnostic Pitfall
Do not confuse plantar warts with corns/calluses based on visual inspection alone. The lateral squeeze test and visual appearance are insufficient 5. Always perform paring or use dermoscopy to confirm the diagnosis, as this fundamentally changes treatment approach—warts require antiviral/destructive therapy while corns/calluses require mechanical pressure relief 1, 6.