keratoma

角化腫

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/16 00:38:00」(JST)

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This article is about calluses and corns of human skin. For other uses, see Callus (disambiguation).

Callus
Examples of callus found on the toe
Classification and external resources
Specialty	Dermatology
ICD-10	L84
ICD-9-CM	700
MeSH	D002145

A callus (or callosity) is a toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation. Rubbing that is too frequent or forceful will cause blisters rather than allow calluses to form. Since repeated contact is required, calluses are most often found on feet because of frequent walking. Calluses are generally not harmful, but may sometimes lead to other problems, such as skin ulceration or infection.

Cause

Normally, a callus will form on any part of the skin exposed to friction over a long period of time. For example, people often develop calluses on the middle finger of their dominant hand due to writing with a pen or pencil. Another cause is from playing string instruments like the guitar or the violin; calluses will develop on the four fingers of the hand used in holding the strings down to the fingerboard, and sometimes on the fingers of the hand used for pizzicato or strumming.

Calluses are also very common on the fingers of bass guitar and double bass players who use both the pizzicato and slapping techniques. This also applies to rock climbers on almost all of their fingers. There are many activities that can result in the formation of a callus, which may even be viewed as a badge of experience and commitment to the activity. On the feet, calluses may form on the small toes due to the compression applied by tightly fitting shoes. Activities that are notorious for causing calluses include (but are not limited to) construction work, many sports, wood carving, playing musical instruments, use of a chef's knife, Trikke carving, rock climbing, hiking, martial arts, weight training, BMXing, dancing (especially ballet), chopping wood, and wearing high heels. Tenpin bowlers will often develop calluses on their thumbs and occasionally their middle fingers from frequent bowling. Although often found on the foot (where the most pressure and friction are applied), calluses can occur anywhere on the body as a reaction to moderate, constant "grinding" pressure. It is the natural reaction of the palmar or plantar skin. Too much friction occurring too fast for the skin to develop a protective callus will cause a blister or abrasion instead.

Biologically, calluses are formed by the accumulation of terminally undifferentiated keratinocytes in the outermost layer of skin. Though the cells of calluses are dead, they are quite resistant to mechanical and chemical insults due to extensive networks of cross-linked proteins and hydrophobic keratin intermediate filaments containing many disulfide bonds.

Sometimes a callus occurs where there is no rubbing or pressure. These hyperkeratoses can have a variety of causes. Some toxic materials, such as arsenic, can cause thick palms and soles. Some diseases, such as syphilis, can cause thickening of the palms and soles as well as pinpoint hyperkeratoses. There is a benign condition called keratosis palmaris et plantaris, which produces corns in the creases of the fingers and non-weight bearing spaces of the feet. Some of this may be caused by actinic keratosis, which occurs due to overexposure to sun or with age and hormonal shifts.

Corns

Main article: Corn (medicine)

Painful corns

A corn (or clavus, plural clavi) is a specially shaped callus of dead skin that usually occurs on thin or glabrous (hairless and smooth) skin surfaces, especially on the dorsal surface of toes or fingers. They can sometimes occur on the thicker palmar or plantar skin surfaces. Corns form when the pressure point against the skin traces an elliptical or semi-elliptical path during the rubbing motion, the center of which is at the point of pressure, gradually widening. If there is constant stimulation of the tissue producing the corns, even after the corn is surgically removed, the skin may continue to grow as a corn.

The hard part at the center of the corn resembles a funnel with a broad raised top and a pointed bottom. Because of their shape, corns intensify the pressure at the tip and can cause deep tissue damage and ulceration. The scientific name for a corn is heloma (plural helomata). A hard corn is called a heloma durum, while a soft corn is called a heloma molle.

The location of the soft corns tends to differ from that of hard corns. Hard corns occur on dry, flat surfaces of skin. Soft corns (frequently found between adjacent toes) stay moist, keeping the surrounding skin soft. The corn's center is not soft however, but indurated.

The specific diagnostic workup and treatments for corns may differ substantially from other forms of calluses.

Prevention

Corns and calluses are easier to prevent than to treat. When it is not desirable to form a callus, minimizing rubbing and pressure will prevent callus formation. Footwear should be properly fitted, gloves may be worn, and protective pads, rings or skin dressings may be used. People with poor circulation or sensation should check their skin often for signs of rubbing and irritation so they can minimize any damage.

Treatment

A person with callus at the barber surgeon's, 17th century

Calluses and corns may go away by themselves eventually, once the irritation is consistently avoided. They may also be dissolved with keratolytic agents containing salicylic acid, sanded down with a pumice stone or filed down with a callus shaver, or pared down by a professional such as a podiatrist or a foot health practitioner.

Diabetes

People with diabetes face special skin challenges. Because diabetes affects the capillaries, the small blood vessels which feed the skin, thickening of the skin with callus increases the difficulty of supplying nutrients to the skin. Callus formation is seen in high numbers of patients with diabetes, and together with absent foot pulses and formation of hammer toe, this may be an early sign of individuals at an increased risk for foot ulcers.

The stiffness of a callus or corn, coupled with the shear and pressure that caused it, may tear the capillaries or adjoining tissue, causing bleeding within the callus or corn. Often, bleeding within a callus is an early sign of diabetes, even before elevated blood sugars may be noticed. Although the bleeding can be small, sometimes small pools of blood or hematoma are formed. The blood itself is an irritant, a foreign body within the callus that makes the area burn or itch. If the pool of blood is exposed to the outside, infection may follow. Infection may also lead to ulceration. Fortunately, this process can be prevented at several places. Diabetic foot infections are the leading cause of diabetic limb amputation.

Other meanings

In botany, the term is also used to describe a condition of thickened surfaces of leaves or other plant parts. A callus also can refer to an undifferentiated plant cell mass grown on a culture medium, which can be put into a bioreactor to produce genetically identical cells. This is a type of tissue culture, and can be started from almost any part of the plant, although tissues taken from the vicinity of meristems usually produce the best results.

The term has also been used in orthopedic medicine to describe heterogeneous tissue involved in the intermediate stages of bone healing.

See also

• Hyperkeratosis
• Callosity
• Catagmatic

Notes

References

• Taber's Cyclopedic Medical Dictionary, 15th Edition, CL Thomas, M.D., M.P.H., editor, F.A. Davis Company, Philadelphia, PA, 1985.
• The Merck Manual of Medical Information, Home Edition, R Berkow, M.D., et al., editors, Merck Research Laboratories, Whitehouse Station, NJ, 1997.

External links

For a definition of the word "callous", see the Wiktionary entry callous.

• MayoClinic.com - Corns and calluses
• How To Remove Calluses - Corns and calluses
• CallusRemoverHQ.com - Callus Shavers

UpToDate Contents

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English Journal

• Four-class classification of skin lesions with task decomposition strategy.

• Shimizu K, Iyatomi H, Celebi ME, Norton KA, Tanaka M.
• IEEE transactions on bio-medical engineering.IEEE Trans Biomed Eng.2015 Jan;62(1):274-83. doi: 10.1109/TBME.2014.2348323. Epub 2014 Aug 15.
• This paper proposes a new computer-aided method for the skin lesion classification applicable to both melanocytic skin lesions (MSLs) and nonmelanocytic skin lesions (NoMSLs). The computer-aided skin lesion classification has drawn attention as an aid for detection of skin cancers. Several researche
• PMID 25137721

• From actinic keratosis to squamous cell carcinoma: Evidence of morphologic and biologic progression.

• Ruini C1, Witkowski AM1, Cesinaro A2, Teixeira De Carvalho N1, Pellacani G3.
• Journal of the American Academy of Dermatology.J Am Acad Dermatol.2015 Jan;72(1 Suppl):S8-S10. doi: 10.1016/j.jaad.2014.02.046.
• PMID 25500054

• Regression of seborrheic keratosis in a dermoscopic follow-up series.

• Fikrle T1, Pizinger K2.
• Journal of the American Academy of Dermatology.J Am Acad Dermatol.2015 Jan;72(1 Suppl):S66-7. doi: 10.1016/j.jaad.2014.09.005.
• PMID 25500049

Japanese Journal

• K1テイルドメインの変異によるIchthyosis hystrix

• 山本 明美,Sprecher E,Richard G
• 角化症研究会記録集 16, 60-62, 2002-02
• … 出版社版当所Vohwinkel's keratoma hereditarium mutilansと診断されていた1家系が実際にはCurth-Macklin型Ichthyosis hystrixであり,その病因がテイルドメインの変異であった事例を報告した …
• NAID 120001025383

• 耳介・外耳道良性腫瘍116例の検討

• 村岡 道徳,兵頭 哲裕,若見 暁樹,中井 義明
• 耳鼻咽喉科臨床 88(5), 591-595, 1995-05-01
• … A few patients had hemangioma simplex, strawberry mark, senile keratoma, seborrheic keratoma, sebaceous nevus, papilloma, enchondroma, fibroneuroma, cyst or keloid. …
• NAID 10005603765

• Delayed diagnosis and fate of congenital cholesteatoma (keratoma)

• GRUNDFAST KM.
• Arch Otolaryngol Head Neck Surg 121, 903-907, 1995
• NAID 10005608638

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★リンクテーブル★

リンク元	「角化腫」
拡張検索	「angiokeratoma」

「角化腫」

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keratoma

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角化異常症

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　　[★] 被角血管腫、血管角化腫