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Callosities can be painful, and the symptoms may be so intense as to seriously affect a person's gait, choice of footwear, and activities. While many patients seek symptomatic relief from a chiropodist or pharmacist, doctors should be familiar with the diagnosis and management of these common disorders.
Nomenclature
Many medical textbooks fail to clearly differentiate between the various types of keratotic lesions. Furthermore, the terminology used by British surgeons, American surgeons, rheumatologists, dermatologists, and podiatrists is different and sometimes confusing. 1 2 3 4 5 6 7 8 9 The definitions below reflect the most widely accepted use of the terms (fig 1 ).
CALLOSITY
A callosity occurs when the process of keratinisation, which maintains the stratum corneum of the skin as a horny protective cover, becomes overactive due to shearing or compressive forces. This is a normal protective response-as seen in the hands of manual labourers and the feet of those who walk barefoot-and a callosity becomes pathological only when it is so large as to cause symptoms.
CORN
A corn represents a circumscribed, sharply demarcated area of traumatic hyperkeratosis. It has a visible translucent central core which presses deeply into the dermis, causing pain and sometimes inflammation. The term heloma (Greek helus, a stone wedge) is often used by podiatrists to denote a corn (Latin cornu, horn).
The hard corn (heloma durum) represents the classic corn-a dry horny mass most commonly found on the dorsolateral aspect of the fifth toe or the dorsum of the interphalangeal joints of the lesser toes (fig 2 ). It is often termed the digital corn.
The soft corn (heloma molle) is an extremely painful lesion that occurs only interdigitally and is probably best termed an interdigital corn. It is essentially a corn that has absorbed a considerable amount of moisture from sweat, leading to characteristic maceration (fig 3 ) and sometimes secondary fungal or bacterial infection. It is most common in the fourth interdigital space. Sometimes two opposing lesions can be found and are termed "kissing lesions."
CALLUS
A callus is a broad based, diffuse area of hyperkeratosis of relatively even thickness, most commonly found under the metatarsal heads. A callus is less circumscribed than a corn, is usually larger, does not have a central core, and...