| Callosity= الشثن |
|
|
Corns and Calluses
EPIDEMIOLOGY Every human being, with the exception of the non-weight-bearing infant, is vulnerable to the development of corns and calluses, because the skin is subjected to regular mechanical stress. The prevalence of corns and calluses can be readily appreciated by the number of nonprescription products aimed at reducing or preventing them—a billiondollar market annually. The earliest known discussion of these lesions can be found in the writings of Cleopatra, who authored a textbook on cosmetics.1 Corns and calluses have plagued humankind since antiquity, affecting those at all socioeconomic levels. Certain foot types and regions are prone to mechanically induced skin thickening, regardless of race, gender, or age. ETIOLOGY AND PATHOGENESIS Corns and calluses result from the prolonged application of excessive mechanical shear or friction forces to the skin. In theory, these forces induce hyperkeratinization, which leads to a thickening of the stratum corneum, although the precise mechanism by which this occurs remains unknown. If the abnormal forces are distributed over a broad area (i.e., more than 1 cm2), a callus develops. In contrast, a corn will form if the same forces are applied to a focused location, with the lamellae of the stratum corneum becoming impacted to form a hard central core known as the radix or nucleus . Mechanical keratoses are not determined genetically. Heredity does play a role, however, in configuring the individual's skeletal architecture. A family history of bony abnormality or ligamentous laxity predisposes the person to the presence of sites of increased cutaneous friction or shear. The prevalence of these lesions has also proven to be significantly higher in females, certain ethnic groups, and mentally ill patients. CLINICAL FINDINGS History Corns and calluses produce painful symptoms often described as burning, especially when the affected area is weight bearing and/or shoes are worn. This discomfort is thought to result from microtearing of the thickened, inflexible skin. Cutaneous Lesions Corns [clavi or helomata (singular: clavus or heloma)] and calluses [tylomata (singular: tyloma)] are, respectively, keratotic papules and plaques that occur in areas that are subject to sustained excessive mechanical shear or friction forces. Related Physical Findings The lesions occur in predictable pedal locations, corresponding to a structural deformity or biomechanical fault. Crookedness of the lesser toes leads to prominence of the proximal and/or distal interphalangeal joints. Keratoses can therefore form either dorsal to those joints, between the toes, at the distal end of the toe, or on the lateral aspect of the fifth toe and/or toenail (lateral toenail corn, also known as Durlacher's corn; see eFig. 97-1.1 in on-line edition). Interdigital corns can be hard when they are adjacent to the interphalangeal joint(s) (see eFig. 97-1.2 in on-line edition) or soft when deep within the fourth interdigital space. The softness of latter last corn results from trapped perspiration, which leads to maceration of the keratotic tissue .
In patients with bunions (hallux valgus), a callus usually forms at the medioplantar aspect of the hallux. During gait, the individual rolls off that portion of the great toe because of its incorrect position. The skin is subsequently
Other favored locations for lesser metatarsal head keratosis include the following:
Another variant of corn is that referred to as heloma miliare, or seed corn. This title is derived from the clinical appearance of these corns: multiple guttate keratoses that are easily pared. When seamed nylon hosiery was fashionable, this garment was considered the causative factor. However, patients still present with seed corns even though they have never worn seamed stockings. ▪ HISTOPATHOLOGY In contrast to nonmechanically induced keratoses, corns and calluses exhibit changes within the epidermis, dermis, and adipose layer. Corns demonstrate a parakeratotic plug within the stratum corneum, with a pressure-related loss of the stratum granulosum as well as atrophy of the stratum malpighii. The dermis displays significant fibrosis, dilated eccrine ducts and blood vessels, hypertrophied nerves, and scar tissue replacement of subcutaneous fat. Overall, the histologic changes in calluses are less pronounced, and include a thickened stratum corneum but intact stratum granulosum. Because corns and calluses are the result of mechanical friction and shear alone, there are no associated hematologic, chemical, serologic, or immunohistochemical abnormalities. PROGNOSIS AND CLINICAL COURSE If left untreated, corns and calluses result in painful ambulation and also in
Differential Diagnosis of Corns and Calluses
The need for lower-extremity amputation is a dominant fear in most diabetic patients. Such amputations are most often preceded by a history of foot ulceration . Although a number of co-morbidities contribute to the development of ulceration (e.g., peripheral vascular disease, neuropathy, and limited joint mobility), minor trauma via repetitive pressure is the pivotal precipitating event. As markers of repetitive friction and shear, corns and calluses in the diabetic foot are of special significance. Simple débridement of these hyperkeratotic lesions decreases peak plantar pressures by as much as 26 percent. In a retrospective review of more than 200 diabetic foot ulcerations, patients who had their corns and calluses pared frequently experienced a statistically significant decrease in the incidence of foot ulceration, hospitalization, and surgical intervention. Hemorrhage within a corn or callus is an especially ominous sign, indicating subcutaneous breakdown with a strong potential for ulceration. Therefore, ulcer care should include paring of calluses. The use of proper footwear by the diabetic as well as the non-diabetic patient may also play a role in not only preventing but also reducing the development of callosities. Shoes should be correctly sized to accommodate the width and length of the patient's foot, and the heel should be elevated minimally if at all to prevent pathology and pain. Treatment
PREVENTION Corns and calluses can be prevented only by reducing or eliminating the mechanical forces that created them. Usually, this is a daunting, if not impossible, task. Repetitive occupational motions are often unavoidable, patients are commonly reluctant to alter shoe styles, and osseous architecture is predetermined through heredity
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
