Clinical Presentation of Corns and Calluses

Diagnostic Hallmarks Distribution: bony prominences of the feet Absence of black dots and pinpoint bleeding when lesions are pared Clinical Presentation The volar epithelium of the palms, soles, and digits is embryologically designed to undergo a proliferative and hyperkeratotic response as a protective reaction against chronic trauma. Repeated irritation to these tissues results in acanthosis and massive thickening of the stratum corneum. These histologic changes are reflected clinically by the presence of corns or calluses. Corns appear as sharply marginated, square-shouldered, firm papules 3-10 mm in diameter. They have a slightly roughened surface and are skin colored or somewhat yellow. They overlie the interphalangeal joints of the toes, especially on the dorsilateral surface of the fifth toe, but they also occur on the lateral aspect of the fourth toe.

These latter lesions are sometimes called "soft" corns. A translucent core lacking blood vessels will be visible if the top of any com is pared with a scalpel blade. Calluses are larger lesions with more diffuse, slope-shouldered margins. They, too, are skin colored or slightly yellow and have a slightly roughened surface.

Calluses are most commonly found on the medial side of the great toe, around the edges of the heel, and over the plantar surface of the metatarsal heads. Calluses may, of course, occur on the hand if sufficient, chronic trauma is experienced. Calluses, when pared, also generally reveal a translucent central core, but in any event no black dots (thrombosed capillaries) or pinpoint bleeding spots as are seen in warts are present. Small corns and calluses may be asymptomatic, but larger ones are quite painful. Course and Prognosis Corns and calluses remain in place as long as the trauma that initiated their presence continues.

They disappear spontaneously if and when this trauma can be removed. Pain caused by the thickness and firmness of these lesions sometimes leads to improper foot position while walking. This can, in turn, cause chronic pain in the foot, knee, or hip. Deformity of the toes is sometimes noted. Pathogenesis Corns and calluses occur when chronic rubbing or pressure compresses volar epithelium against a firm bony surface. This irritation causes an increased mitotic rate in the epithelium that, in turn, leads to massive production and retention of stratum corneum cells.

It is the thickened stratum corneum layer that primarily accounts for the bulkiness of the lesions. There is no inherent biologic difference between corns and calluses. Corns occur when sharply localized pressure develops over the narrow radius of the heads of the phalanges.

More diffuse pressure, especially when it occurs over bone surfaces with less curvature or surfaces better protected by a connective tissue cushion, results in the formation of calluses. Therapy The first step in the treatment of corns and calluses is to reduce or remove the source of chronic trauma. For instance, ill-fitting shoes can be discarded, arch supports can be inserted, or metatarsal bars can be added to the sole of the shoes.

Second, the thickened, hyperkeratotic portion of the corn or callus can be removed by paring. Third, the remainder of the lesion can be softened by the daily application of a 5-10% salicylic acid ointment or pad. The second and third steps can be continued indefinitely if the causative trauma cannot be eliminated. On rare occasions, orthopedic procedures are required in order to repair underlying bony abnormalities.

Surgical excision of corns and calluses is best avoided, since it does not get at the cause of the disease and the resultant scarring may be troublesome.

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