Callosity (callus): a plaque of thickened skin.

Corn: sharply demarcated callosity which has developed a central, and often painful, keratin core.

Soft corn: occurs between the toes.

Cause: Pressure and friction due to inappropriate shoes: too tight (soft corns) or loose (callosities), abnormal foot mechanics (elderly, hallux valgus, diabetic neuropathy, rheumatoid arthritis), high levels of activity.

Differential diagnosis: Warts and Verrucae. Callosities have skin markings; warts do not maintain the skin markings. Callosities/corns tender with direct pressure; warts tender with pressure applied from side to side. After paring the skin, callosities have a waxy appearance, corns have a central keratin plug and warts have black thrombosed capillaries.

Management: Well-fitting comfortable flat footwear +/- insoles/pads. Reduce skin thickness (pare down thickened skin with pumice stone or emery paper once/twice per week; Soak skin in warm water for 10-20 mins prior).

Medical treatment: Creams containing salicyclic acid (avoid in diabetic patients) or urea may help reduce skin thickness.

Referral: Podiatrist referral for persistent lesions or high-risk individuals e.g. diabetics:

Corns and callosities (PCDS)