AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Background

Corns, also referred to as clavi, are painful, hyperkeratotic papules of the skin that develop in response to excess pressure on the bony prominences of the feet and toes. Corns are often seen in athletes and in patient populations exposed to uneven friction from footwear or gait abnormalities, including elderly persons, diabetic patients, and amputees. Abnormal foot mechanics, foot deformities, high activity level, and more serious conditions such as peripheral neuropathy also contribute to the formation of corns.¹ Corns are associated with considerable morbidity secondary to pain; fortunately, many treatment and preventative options are available that provide a high rate of mitigation.

Clinically, 3 types of corns have been described. The first is a hard corn, or heloma durum, notable for its dry, horny appearance. It is found most commonly over the interphalangeal joints. The second is a soft corn, or heloma molle, described as such because of its macerated texture secondary to moisture. It is generally found in interdigital locations.^{2, 3} The third type is a periungual corn, and this type occurs near or on the edge of a nail.⁴
 
Corns are often misdiagnosed as calluses, which are also hyperkeratotic skin lesions resulting from excess friction. However, calluses develop from forces distributed over a broad area of skin, whereas corns develop from more localized forces.⁵ Calluses are often considered desirable for some activities (eg, gymnastics, weightlifting), and they lack a central core, which is characteristically revealed in corns upon removal of the upper hyperkeratotic layer of skin. Corns can occur within an area of callus,⁶ such as on the plantar surface.

Pathophysiology

Corns are the result of mechanical trauma to the skin culminating in hyperplasia of the epidermis. Most commonly, friction and pressure between the bones of the foot and ill-fitting footwear cause a normal physiological response—proliferation of the stratum corneum. One of the primary roles of the stratum corneum is to provide a barrier to mechanical injury. Any insult compromising this barrier causes homeostatic changes and the release of cytokines into the epidermis, stimulating an increase in synthesis of the stratum corneum. When the insult is chronic and the mechanical defect is not repaired, hyperplasia and inflammation are common.⁷ With corns, external mechanical forces are focused on a localized area of the skin, ultimately leading to impaction of the stratum corneum and the formation of a hard keratin plug that presses painfully into the papillary dermis, which is known as a radix or nucleus.^{3, 5}

Frequency

United States

Corns are one of the most common foot conditions in the United States, particularly amongst older patients.

International

Corns are common worldwide. Any weight-bearing human is susceptible to the development of corns.

Mortality/Morbidity

The most common symptoms associated with corns are pain upon ambulation and restriction of activity secondary to pain. Corns are generally not associated with mortality; however, recognizing the potential for a maltreated corn, soft corns in particular, to develop into a life-threatening secondary infection (bacterial or fungal) is important in patients with diabetes mellitus or immunosuppression.

See Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; and Diabetic Foot Infections for follow-up information.

Race

An epidemiological study evaluating the prevalence of foot conditions amongst a diverse sample of adults from the northeastern United States revealed a significant difference in rates of corns amongst ethnic groups. African Americans had a significantly higher rate of corns and calluses compared with non-Hispanic white and Puerto Rican participants (70% vs 58% vs 34.1%).⁸

Sex

Amongst elderly populations, both men and women have been reported to wear shoes too narrow for their feet. Women have been reported to wear shoes that are also shorter than their feet. Both narrow and short footwear can lead to the development of corns, in addition to foot deformities.⁹

Age

Hyperkeratotic lesions of the foot (including corns and calluses) have been reported to affect 20-65% of people aged 65 or older.^{8, 10, 11}

CLINICAL

Section 3 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

History

Commonly, a patient reports the development of a localized growth on their foot or toes that causes pain with ambulation or when wearing shoes.⁴

Physical

Corns are typically located between toe clefts, on the plantar aspect beneath  prominent metatarsals, or on the dorsal aspect of toe joints.⁵ The patient’s gait should be observed to identify irregular mechanics.³ Additionally, surrounding erythema and heat may be present if the corn is acutely irritated.² 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 clavi. Warts are tender with pressure applied from side to side.^{4, 6}
• Calluses have a waxy appearance after being pared, whereas corns produce a central keratin plug.⁴ Plantar warts do not have a central core.
• The absence of capillary dotting after paring hard corns distinguishes them from plantar warts.^{3, 12}
• Skin markings can be seen crossing the surface of calluses, but not warts or corns.¹²  

A hard corn is a firm, dry, and tender lesion with a shiny polished surface. If the upper layers are pared away, 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.² 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.² Plantar corns that do not respond to conservative medical treatment are referred to as intractable plantar keratosis.¹³

A soft corn is boggy and macerated so that it appears white. Soft corns usually occur in the fourth interdigital space.²

Causes

Both hard and soft corns are caused by pressure from unyielding structures.² Abnormal mechanical stress may be intrinsic or extrinsic (list adapted from Singh et al, “Callosities, corns, and calluses”³).

• Following are intrinsic factors:
• • Foot deformities (hammer toe, bunion)¹⁴
  • Abnormal foot mechanics (acquired or hereditary)
  • Peripheral neuropathy
• Following are extrinsic factors:
• • Poorly fitting footwear
  • Heavy activity (athletics)

A 2005 study conducted by Menz et al reported that in older populations, plantar pressures are significantly higher under callused regions of the foot.¹⁵ This data supports the idea that increased pressures are related to a hyperkeratotic response and that the target for treatment should be eliminating excess pressures on the foot.

DIFFERENTIALS

Section 4 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Other Problems to be Considered

Porokeratosis plantaris discreta
Keratosis punctata
Palmoplantar keratoderma (acquired or hereditary)
Foreign body
Morton neuroma
Synovitis

WORKUP

Section 5 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Lab Studies

No routine laboratory tests are necessary to evaluate a patient with corns.³ Diabetes mellitus, tertiary lues, and other causes of neuropathy should be excluded.

Imaging Studies

Radiographs of the feet in a weight-bearing position are useful for identifying bony prominences and the presence of underlying pathology contributing to foot pain.¹⁶ However, a physical examination may be sufficient to evaluate smaller toe abnormalities.¹⁶

Other Tests

Pressure studies (eg, pedobarography) may help define the exact location of increased plantar pressure.³

Histologic Findings

Corns demonstrate epidermal hyperplasia with a thick and compact stratum corneum. Whereas calluses demonstrate only orthokeratosis, parakeratosis may be present in corns, and biopsy specimens demonstrate an endophytic cup shape. The granular cell layer may be decreased or absent.^{5, 6} The dermis may occasionally show fibrosis with hypertrophied nerves and scar tissue replacing subcutaneous fat.⁵

TREATMENT

Section 6 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Medical Care

When treating hard corns, the primary objective is to debulk or pare the lesion without drawing blood. Following preparation of the skin with alcohol or iodine, a No. 15 surgical blade can be used with or without anesthesia to gradually remove sequential layers of keratin.³ The final treatment goals are to remove the central keratin core for short-term pain relief and to reshape the skin to provide long-term prevention of excess friction.^{4, 5} Regular debridement in high-risk populations, such as diabetic patients, may decrease the incidence of ulceration and, consequently, the need for surgical intervention.¹⁷

Soft corns are often difficult to treat because they develop from underlying pressures in between the fourth and fifth digit, caused by bony prominences.² Soft corns are best treated with properly fitting footwear and better foot hygiene in order to decrease the likelihood for infection. Applying an antifungal or antibacterial powder after washing the area and using lamb’s wool or a toe spacer are additional techniques used to treat soft corns.⁵ A good option in patients with coexisting dermatophytosis complex is 20% aluminum chloride hexahydrate solution (Drysol).

Following are additional treatment modalities:  

• Keratolytics: Products that can be applied to affected areas include 40% salicylic acid pads and plaster, 40% urea cream, and 12% lactic acid cream.^{5, 18} However, patients with peripheral neuropathies should avoid or use topical salicylic acid with caution.¹⁹ 
• Filler injections: A retrospective evaluation of the use of fluid silicone in treating loss of plantar fat reveals a unique treatment option for corns and calluses.^{20, 21, 22} Balkin reports he treated more than 1500 patients from 1964-2005 with silicone injections to digital and plantar sites. He found that 60-80% experienced some form of pain relief and elimination of calluses. Booster treatments are often needed, and the only complication reported was skin discoloration.²² Injection of 0.1 mL of medical-grade liquid silicone below a clavus and above the bone has been reported to have good results,²³ but it is not presently approved by the US Food and Drug Administration.²⁴ Whether other filler substances can achieve the same success is unknown.

Overall, removing or adjusting the mechanical stress causing the corn—finding footwear that matches the length and width of a foot—is the first step towards treatment of this condition.^{3, 25} Patient awareness of his or her footwear is critical to the prevention of future corns. Conservative treatment can be continued at home and may consist of using a pumice stone for minor debridement, practicing good foot hygiene, and using soft spacers or a silicone sleeve, which can be bought at most retail stores.^{2, 18}

Surgical Care

Surgery to remove the bony prominences is indicated only if all conservative measures fail.^{3, 4, 14} Surgical procedures include bunionectomy, syndactylization, osteotomy, and arthroplasty.^{2, 14} Long-term improvement for lateral fifth-toe corns and interdigital corns has been achieved with partial and complete condylectomy.¹⁴

Consultations

If patients do not respond to conservative treatment, further evaluation by a podiatrist or orthopedic surgeon is recommended. Extensive orthoses are available to help remove mechanical stresses on the foot, and an orthopedist or podiatrist should be consulted.

Diet

Weight loss may reduce pain from corns and improve biomechanics in patients who are obese.

Activity

Patients are advised to reduce or eliminate certain mechanical forces or motions. However, certain activities, particularly work related, may be unavoidable or patients may be reluctant to make the necessary changes.

MEDICATION

Section 7 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Keratolytic agents

These agents cause the cornified epithelium to swell, soften, macerate, and then desquamate.

FOLLOW-UP

Section 8 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Further Outpatient Care

Follow-up care is important to ensure control of the hyperkeratosis because patients may require regular, repeated applications of keratolytic agents in conjunction with careful paring.

Patients with special health concerns, including diabetic patients, amputees, and elderly persons, may require more frequent follow-up visits in order to decrease the likelihood of a more catastrophic complication, particularly secondary bacterial infection, from the initial lesion.

Deterrence/Prevention

Deterrence and prevention includes the use of corn pads, web spacers, and properly fitting shoes (see Pathophysiology and Medical Care). Patients can treat their corns at home using a pumice stone to regularly debulk the lesion after a shower, when the skin is soft.

Complications

Complications include secondary bacterial or fungal infection in patients with diabetes or in patients with immunosuppression (see Mortality/Morbidity). With deep paring, be aware of the risk of bleeding and infection.⁴

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

Prognosis

Recurrence is common.

Patient Education

For excellent patient education resources, visit eMedicine's Foot Care Center. Also, see eMedicine's patient education article Corns and Calluses.

MISCELLANEOUS

Section 9 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Medical/Legal Pitfalls

Close follow-up care is extremely important in patients with diabetes and patients with immunosuppression to prevent the occurrence of secondary bacterial or fungal infection.

ACKNOWLEDGMENTS

Section 10 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

The authors and editors of eMedicine gratefully acknowledge the contributions of previous authors, (1) Ali Hendi, MD, (2) Douglas W. Kress, MD, and (3) Roger Patrick, MD, to the development and writing of this article.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Media file 1:  Hard corn on the lateral surface of fifth toe. Courtesy of James K. DeOrio, MD.
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Media file 2:  Hard corn over the proximal interphalangeal joint of second toe. Courtesy of James K. DeOrio, MD.
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Media file 3:  Calluses on the palmar surface of the hands of a body builder. Courtesy of James K. DeOrio, MD.
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Media type:  Photo

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

1. Freeman DB. Corns and calluses resulting from mechanical hyperkeratosis. Am Fam Physician. Jun 1 2002;65(11):2277-80. [Medline].
2. Murphy GA. Lesser Toe Abnormalities: Corns (Helomata and Clavi). In: Canale ST, ed. Canale: Campbell's Operative Orthopaedics. 10th. St. Louis, Mo: Mosby; 2003:4063-5.
3. Singh D, Bentley G, Trevino SG. Callosities, corns, and calluses. BMJ. Jun 1 1996;312(7043):1403-6. [Medline].
4. Snider RK. Corns and Calluses. In: Greene WB, ed. Essentials of Musculoskeletal Care. 2^nd ed. Rosemont, Ill: American Academy of Orthopaedic Surgeons; 2001:437-41.
5. DeLauro TM, DeLauro NM. Corns and Calluses. In: Wolff K, Goldsmith LA, Katz SI, Gilchrest BA, Paller AS, Leffell DJ, eds. Fitzpatrick's Dermatology in General Medicine. 7^th ed. New York, NY: McGraw-Hill; 2008:97.
6. Kennedy CTC, Burd DAR. Mechanical and Thermal Injury. In: Burns T, Breathnach SM, Cox N, Griffiths CE, eds. Rook's Textbook of Dermatology. 7^th ed. London, England: Blackwell Science; 2004:22.
7. Williams ML, Elias PM. Enlightened therapy of the disorders of cornification. Clin Dermatol. Jul-Aug 2003;21(4):269-73. [Medline].
8. Dunn JE, Link CL, Felson DT, Crincoli MG, Keysor JJ, McKinlay JB. Prevalence of foot and ankle conditions in a multiethnic community sample of older adults. Am J Epidemiol. Mar 1 2004;159(5):491-8. [Medline].
9. Menz HB, Morris ME. Footwear characteristics and foot problems in older people. Gerontology. Sep-Oct 2005;51(5):346-51. [Medline].
10. Black JR, Hale WE. Prevalence of foot complaints in the elderly. J Am Podiatr Med Assoc. Jun 1987;77(6):308-11. [Medline].
11. Benvenuti F, Ferrucci L, Guralnik JM, Gangemi S, Baroni A. Foot pain and disability in older persons: an epidemiologic survey. J Am Geriatr Soc. May 1995;43(5):479-84. [Medline].
12. Habif TP. Warts, Herpes Simplex and other Viral Infections. In: Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4^th ed. St. Louis, Mo: Mosby; 2004:374-5.
13. Mann RA, DuVries HL. Intractable plantar keratosis. Orthop Clin North Am. Jan 1973;4(1):67-73. [Medline].
14. Coughlin MJ, Kennedy MP. Operative repair of fourth and fifth toe corns. Foot Ankle Int. Feb 2003;24(2):147-57. [Medline].
15. Menz HB, Zammit GV, Munteanu SE. Plantar pressures are higher under callused regions of the foot in older people. Clin Exp Dermatol. Jul 2007;32(4):375-80. [Medline].
16. Coughlin MJ. Common causes of pain in the forefoot in adults. J Bone Joint Surg Br. Aug 2000;82(6):781-90. [Medline].
17. Sage RA, Webster JK, Fisher SG. Outpatient care and morbidity reduction in diabetic foot ulcers associated with chronic pressure callus. J Am Podiatr Med Assoc. Jun 2001;91(6):275-9. [Medline].
18. Cordoro KM, Ganz JE. Training room management of medical conditions: sports dermatology. Clin Sports Med. Jul 2005;24(3):565-98, viii-ix. [Medline].
19. Foster A, Edmonds ME, Das AK, Watkins PJ. Corn cures can damage your feet: an important lesson for diabetic patients. Diabet Med. Dec 1989;6(9):818-9. [Medline].
20. Balkin SW. Silicone injection for plantar keratoses. Preliminary report. J Am Podiatry Assoc. Jan 1966;56(1):1-11. [Medline].
21. Balkin SW. Injectable silicone and the foot: a 41-year clinical and histologic history. Dermatol Surg. Nov 2005;31(11 Pt 2):1555-9; discussion 1560. [Medline].
22. Field LM. Letter: injectable silicone for painful interdigital neurovascular clavi and verrucae. Dermatol Surg. Dec 2006;32(12):1535. [Medline].
23. Narins RS, Beer K. Liquid injectable silicone: a review of its history, immunology, technical considerations, complications, and potential. Plast Reconstr Surg. Sep 2006;118(3 Suppl):77S-84S. [Medline].
24. Richards RN. Calluses, corns, and shoes. Semin Dermatol. Jun 1991;10(2):112-4. [Medline].
25. Dockery GL, Nilson RZ. Intralesional injections. Clin Podiatr Med Surg. Jul 1986;3(3):473-85. [Medline].

Article Last Updated: Jan 18, 2008