Sections

Corns (Clavus)

Presentation

History

A clavus forms because of inappropriate distribution of pressure onto a specific site, usually of the foot.^[11]A localized callosity of the soles, which does not resolve, is termed plantar callus, heloma, tyloma, keratoma, or plantar corn. When callosities occur over one or more lateral metatarsals, they are termed intractable plantar keratoses.

Physical Examination

Corns are typically located between toe clefts, on the plantar aspect beneath prominent metatarsals, or on the dorsal aspect of toe joints.^[12]The patient’s gait should be observed to identify irregular mechanics.^[6]Additionally, surrounding erythema and heat may be present if the corn is acutely irritated.^[5]Multiple physical signs, as follows, can be evaluated in order to differentiate between a clavus, callus, and wart:

Both plantar warts and hard corns can be tender, and both occur on the pressure points of the sole.
Direct pressure generally causes tenderness in a callus and corn. Warts are tender with pressure applied from side to side.^{[7, 15]}
Calluses have a waxy appearance after being pared, whereas corns produce a central keratin plug.^[7]Plantar warts do not have a central core.
The absence of capillary dotting after paring hard corns distinguishes them from plantar warts.^{[6, 52]}
Skin markings can be seen crossing the surface of calluses, but not warts or corns.^[52]

A hard corn is a firm, dry, and tender lesion with a shiny polished surface. If the upper layers are pared, a small, 1- to 2-mm translucent central core may be seen within the base of the lesion. Hard corns usually occur on the dorsolateral aspect of the fifth toe.^[5]A plantar corn is a type of hard corn most commonly associated with a central core. These corns are located beneath the metatarsal heads of the toes.^[5]Plantar corns that do not respond to conservative medical treatment are referred to as intractable plantar keratosis.^[53]Note the image below.

Hard corn on the lateral surface of fifth toe. Courtesy of James K. DeOrio, MD.

View Media Gallery

A soft corn is boggy and macerated so that it appears white. Soft corns usually occur in the fourth interdigital space.^[5]

Examination of patients should include assessment of the types of footwear worn, activities performed, gait, and current home therapy or previously prescribed therapy.

Lesions should be palpated and pared to look for underlying blood vessels (black dots or pinpoint bleeding), which are seen in warts, and to look for underlying ulcerations, as seen in neurovascular ulcerations (especially in patients with diabetes).

Paring of callosities or corns, as opposed to plantar warts, should reveal normal dermatoglyphics.^[10]

Callosities are generally more painful with direct pressure, whereas warts are more painful with lateral pressure.^[54]

Pedobarographic studies are pressure assessments that may be used to detect an altered distribution of foot pressure. MRI may delineate diabetic foot problems more clearly.

Biopsy of lesions reveals hyperkeratosis and, occasionally, mucin deposition.

Complications

Complications include secondary bacterial or fungal infection in patients with diabetes or in patients with immunosuppression. With deep paring, be aware of the risk of bleeding and infection.^[7]

Corns are often in close proximity to joints and bones, increasing the chances for septic arthritis or osteomyelitis to occur if left untreated.

Patients, particularly patients with diabetes, may have ulcerations from chronic pressure. This can lead to infection and cellulitis.

Maceration and tinea pedis also may occur.

Differential Diagnoses

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Media Gallery

Hard corn on the lateral surface of fifth toe. Courtesy of James K. DeOrio, MD.
Hard corn over the proximal interphalangeal joint of second toe. Courtesy of James K. DeOrio, MD.
Calluses on the palmar surface of the hands of a body builder. Courtesy of James K. DeOrio, MD.
Screwdriver operator's callus (ie, clavus).

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Table. Clavus Formation Named for Specific Etiology or Location

Table. Clavus Formation Named for Specific Etiology or Location

Vernacular Term	Location	Association
Jeweler's callus, cherry pitter's thumb,^[16]cameo engraver's corn^[17]	Thumb	Digital changes, including callosities related to repetitive use of fine jeweler's instruments, which also may be seen with the use of cherry-pitting tools
Weight lifter's callus^[18]	Callosities over the palmar metacarpophalangeal joints	Caused by the friction of weight-lifting apparatus (This also may be seen in athletes who participate in crew.)
Prayer callus^{[19, 20]}	Callosity on the forehead	From kneeling prayer with the hands on the forehead
Cigarette lighter's thumb^[21]	Hyperkeratosis of the radial aspect of the thumb	Caused by excessive cigarette lighter flicking
Knuckle pads^[22]	Hyperkeratosis over the knuckles	Caused by boxing training
Russell sign^[23]	Callosities of the dorsum of the hand over the metacarpophalangeal and interphalangeal joints	Caused by the friction involved with self-induced emesis in bulimia nervosa
Screwdriver operator's clavus^[24]	Palmar surface of the hand	Occurs at the site of contact with a screwdriver handle
Spine bumps	Hyperkeratosis over the spinal column	Caused by dancing with spinning on one's back
Hairdresser's hand	First finger on dominant hand	Callus formation at the site of friction caused by scissors around the first finger on the dominant hand
Sucking calluses^[25]	Lip, hand, or foot of a newborn	Callus formation at the site of an area of suction on the lip, hand, or foot of a newborn
Vamp disease^[26]	Feet	Clavus formation due to wearing tight high-heeled shoes
Muay Thai kickboxers^[27]	Feet	Callosities on the forefoot (77.5%), on the plantar first metatarsal (55.3%), and on the big toe (33.3%)

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Author

Nanette B Silverberg, MD Clinical Professor of Dermatology, Icahn School of Medicine at Mount Sinai; Chief of Pediatric Dermatology, Mt Sinai Health Systems, Mount Sinai St Luke's-Roosevelt Hospital and Mt Sinai Beth Israel Medical Centers

Nanette B Silverberg, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Academy of Pediatrics, American Association of University Women, American Medical Association, American Medical Women's Association, Dermatology Foundation, European Society for Pediatric Dermatology, Pediatric Dermatology Research Alliance, Phi Beta Kappa, Sigma Xi, The Scientific Research Honor Society, Society for Pediatric Dermatology, Vitiligo Support International, Women's Dermatologic Society

Disclosure: Received income in an amount equal to or greater than $250 from: Valeant Pharmaceuticals.

Specialty Editor Board

David F Butler, MD Former Section Chief of Dermatology, Central Texas Veterans Healthcare System; Professor of Dermatology, Texas A&M University College of Medicine; Founding Chair, Department of Dermatology, Scott and White Clinic

David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, Association of Military Dermatologists, Phi Beta Kappa, Texas Dermatological Society

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

Daniel J Hogan, MD Clinical Professor of Internal Medicine (Dermatology), Nova Southeastern University College of Osteopathic Medicine; Investigator, Hill Top Research, Florida Research Center

Daniel J Hogan, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Contact Dermatitis Society, Canadian Dermatology Association

Disclosure: Nothing to disclose.

Richard K Scher, MD Adjunct Professor of Dermatology, University of North Carolina at Chapel Hill School of Medicine; Professor Emeritus of Dermatology, Columbia University College of Physicians and Surgeons

Richard K Scher, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, American Medical Association, The Society of Federal Health Professionals (AMSUS), International Society for Dermatologic Surgery, Noah Worcester Dermatological Society, Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Amy Lynn Basile, DO, MPH Sun Coast Hospital/Largo Medical Center

Amy Lynn Basile, DO, MPH is a member of the following medical societies: American Medical Association, American Osteopathic Association, American Osteopathic College of Dermatology

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Ali Hendi, MD; Douglas W. Kress, MD; and Roger Patrick, MD, to the development and writing of this article.

Corns (Clavus) Clinical Presentation

History

Physical Examination

Complications

References

Tables

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