Maria Isabel Romano Corns and calluses are a painful reaction to pressure or friction on the underlying dermis covering the digital and plantar surfaces of the feet. Areas of excessive pressure or friction lead to hyperkeratotic, thickened skin that forms a padded area of protection for underlying skin structures. Corns, also termed helomas, are of two kinds: soft (heloma molle) and the more common hard (heloma durum). Calluses (tylomas), although unsightly, are less bothersome than corns and are usually a reaction to friction on the metatarsal heads or other bone prominences and may be a response to body weight distribution.1 Calluses are not well circumscribed and lack the central hyperkeratotic painful core that is found in corns. Soft corns stem from hyperkeratotic development in response to excessive pressure or friction. A soft corn is a spongy hyperkeratosis usually found in the interdigital areas of the fourth and fifth toes. The pain associated with soft corns is often extreme because the inflammation excites pressure on the nerve receptors in the dermis. Pressure on the skin over the heads and bases of the condyles of the metatarsals and phalanges results from extrinsic factors, including an improperly fitting toe box, short shoes, and shoes with stiff soles, or from intrinsic factors, such as arthritic changes, fractures, and congenital foot deformity. Both intrinsic and extrinsic factors contribute to the development of a compensatory response of the foot and toes. Downward pressure on the metatarsal heads and contracture of the phalanges set the stage for friction and pressure, leading to corn and callus formation. Both are hard and produce pain as the conical keratin points into the dermis, stimulating painful sensory nerve endings.2 Pain is triggered by development of an underlying bursitis or adventitious bursa that acts as a buffer of protection for the underlying bone.1 Corns typically produce problems when symptoms interfere with the performance of daily activities. Obtaining a good occupational history and inspecting the style and fit of the patient’s customary shoe are important. Inability to move the toes in the toe box or wearing of pointed-toe or high-heeled shoes is frequently reported. Self-treatment by cutting or using over-the-counter plasters to remove the outer horny layer of tissue is common. Soft corns can be extremely painful and are characterized by their white, macerated appearance, which is a result of the absorption of perspiration.3 Secondary infections of interdigital soft corns are common and painful and will often cause additional oozing and inflammation. Corns appear as well-circumscribed, translucent formations of keratin derived from the stratum corneum of the epidermis. Corns and calluses are located in areas of mechanical trauma. The dorsolateral aspect of the fifth toe and the dorsal surface of the distal interphalangeal joints of the second, third, and fourth toes are the areas most commonly affected by pressure. Seed corns are small, localized lesions anywhere on the plantar surface; hard corns are located over bone prominences; soft corns occur between the toes, most often in the fourth web space; and a “pump bump” or Haglund deformity is a bony enlargement on the back of the calcaneus resulting from high arches, a tight Achilles tendon, or walking on the lateral foot aspect.4 Inspection and examination are the only diagnostics generally indicated. Sometimes x-ray studies may be ordered to examine the bony structures of the feet. Hard corns are distinguished from warts by their slow onset, location over bone prominences, and painful response to direct pressure. Other factors include the lack of punctate bleeding when the corn is pared with a No. 15 blade surgical scalpel as well as evidence of furrowed skin lines on magnification that are not present in warts.2 In some instances, radiographs of the bony structures of the feet may be necessary to determine the intrinsic cause of corn and callus formation, such as arthritis, bone prominences, condylar projections, and malunion of an old fracture.5 Diagnostics Corns and Calluses
Corns and Calluses
Definition
Pathophysiology
Clinical Presentation
Physical Examination
Diagnostics and Differential Diagnosis
Corns and Calluses
Chapter 49
