Corns and calluses
What are corns?
- Corn are sharply demarcated keratotic painful lesions resulting from repeated mechanical trauma due to friction or pressure forces leading to thickening. Corns mostly occurs on bony prominences. Feet or hands may be affected. Corns may interfere with mobility.
- Corns can occur within an area of callus.
What is callus?
A callus is a broad‐based diffuse area of hyperkeratosis of relatively even thickness, usually under the metatarsal heads. Callus is usually painless.
What are the predisposing factors?
- Ill-fitting footwear.
- Bony protuberances.
- Abnormal biomechanical foot function.
- Specific activities that involve repetitive activity.
What are the types of corns?
- Soft corns which are usually located in the interdigital web spaces.
- Hard corns are mostly found on the dorsal aspects of the toes.
- Seed corns
How corns/calluses occur?
Frequent friction and pressure of the skin overlying bony prominences may lead to ulceration. As a protective technique, the skin produces thick keratin layers.
How to differentiate between corns, calluses and warts?
- Warts
- Gentle paring with a blade will reveal thrombosed capillaries (black dots)and there may be multiple bleeding points on additional paring.
- The plantar skin markings are interrupted.
- Koilocytosis is characteristic histologically
- Corns
- Gentle paring with a blade will reveal central whitish- yellow core will be evident.
- The plantar skin markings are preserved.
- Histologically, there is acanthosis and parakeratosis , in addition to loss of granular layer. Dense fibrous tissue with hypertrophied nerves may be present in the dermis.
- Callus
- Gentle paring with a blade will reveal layers of yellowish keratin.
- The plantar skin markings are accentuated.
- Histologically, there is thick, compact stratum corneum, somtimes with parakeratosis over the dermal papillae and there may be expansion of the granular layer. Dermis may show increased fibrosis and collagen around neurovascular bundles.
Treatment options
- Measures should be taken to eliminate friction and pressure on the skin.
- Shoes should be comfortable and well-fitting.
- Orthopedic consultation for bone deformities may be needed and surgical correction may be done in some cases.
- Careful and regular paring will help relieving the pain.
- The use of a toe separator is advised for soft corns.
- Filing after warm water soaking can be performed periodically.
- keratolytic agents (e.g. 40% salicylic acid pads; 6% salicylic acid, 10–40% urea, or 12% ammonium lactate creams), from daily to twice weekly, depending on strength.
- Salicylic-containing plasters should be avoided in patients with peripheral neuropathy (e.g. diabetic patients).
- Simple debridement in combination with a topical application of 1% cantharidin, 30% salicylic acid and 5% podophyllin was effective for treating calluses.
- Urea‐based products (20% to 50%) may help in managing callus.
- Laser treatment may be useful for selected cases.
- For recalcitrant lesions : consider x-ray to look for exostoses and referral to orthopedic or podiatric surgeon.
References
- Dermatology , Edited by Jean L. Bolognia , Julie V. Schaffer , Lorenzo Cerroni Fourth edition: Elsevier, 2018, ISBN 978–0‐7020–6275–9.
- Griffiths, C., Barker, J., Bleiker, T. O., Chalmers, R., & Creamer, D. (Eds.). (2016). Rook’s textbook of dermatology. John Wiley & Sons.
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