Peer Reviewed

Photo Essay

An Atlas of Nail Disorders, Part 7

Alexander K. C. Leung, MD1,2 • Benjamin Barankin, MD3 • Kin Fon Leong, MD4 • Amy Ah-Man Leung, MD5 • Alex H. C. Wong, MD1

1University of Calgary, Calgary, Alberta, Canada

2Alberta Children’s Hospital, Calgary, Alberta, Canada
3Toronto Dermatology Centre, Toronto, Ontario, Canada
4Pediatric Institute, Kuala Lumpur General Hospital, Kuala Lumpur, Malaysia
5Department of Family Medicine, University of Alberta, Edmonton, Alberta, Canada

Leung AKC, Barankin B, Leong KF, Leung AA-H, Wong AHC. An atlas of nail disorders, part 7. Consultant. 2020;60(5):e4. doi:10.25270/con.2020.05.00004

The authors report no relevant financial relationships.

Alexander K. C. Leung, MD, #200, 233 16th Ave NW, Calgary, AB T2M 0H5, Canada (

This article is part 7 of a 15-part series of Photo Essays describing and differentiating conditions affecting the nails. Parts 8 through 15 will be published in upcoming issues of Consultant. To access previously published articles in the series, visit the Consultant archive at and click the “Journals” tab.

Pincer Nail

Pincer nail is characterized by transverse overcurvature of the nail plate along the longitudinal axis of the nail, progressively pinching the nail bed distally.1,2 Characteristically, the curvature increases from proximal to distal, giving it a trumpet-like appearance (Figure).1 The condition was first described in 1950 by Frost, using the term incurvated nail.3 The term pincer nail was coined by Cornelius and Shelley in 1968.4 The big toenails are most often affected, but other toenails may also be involved.1,5 The condition is rare on fingernails.1

Pincer nail

It is believed that the pincer nail deformity results from enlargement of the base of the distal phalanx.6 Because the nail matrix is firmly attached to the nail plate, the increase in tissue results in a reduced curvature of the nail plate proximally and greater curvature distally.6 The transverse overcurvature results in impingement of the distal nail bed between the free lateral edges of the nail plate.7 Pincer nail can cause pain in the affected digit by constriction of the deformed nail plate.7,8 Yabe devised a curvature index to assess the severity of the deformity.9  The curvature index is calculated by dividing the traced length of the nail tip by the apparent width of the nail tip.9

Pincer nail may be inherited or acquired. Hereditary pincer nails are rare and typically symmetric.1 Both an autosomal dominant and autosomal recessive mode of inheritance have been described.10,11 Although hereditary pincer nails may be an isolated finding, they can be a manifestation of certain syndromes, including yellow nail syndrome, Clouston syndrome, epidermolysis bullosa simplex (Dowling-Meara type), and hidrotic ectodermal dysplasia.6,12

In contrast, acquired pincer nails are often asymmetric. Mechanical trauma of the nail unit (eg, from ill-fitting shoes, placing excess upward mechanical force on the first toe pad during walking) is the most common cause of acquired pincer nails.2,6,13,14 Other acquired causes include psoriasis, onychomycosis, osteoarthritis of the distal phalanx, arteriovenous fistula in the forearm, chronic renal failure, systemic lupus erythematosus, Kawasaki disease, amyotrophic lateral sclerosis, medications (eg, β-blockers, pamidronate), tumors of the nail apparatus (eg, subungual exostosis, mucus cyst, implantation cyst), and gastrointestinal tract malignancy.1,6,8,12,15-22

Complications of pincer nail deformity include pain, cosmetic disfigurement, interference with wearing shoes, paronychia, onychomycosis, and rarely, osteomyelitis of the distal phalanx.1,23 The deformity also can have an adverse effect on quality of life.

In acquired cases, the shape of the nail plate often returns to normal when the underlying cause resolves. Indications for treatment include pain, cosmesis, and interference with wearing shoes.1 Treatment is usually conservative when the deformity is mild to moderate. Conservative modalities of treatment include topical application of high-concentration (eg, 40%) urea, grinding of the nail plate, placement of a plastic device, and use of superelastic nickel-titanium to bend the deformity to its normal shape.24 More severe cases may require surgical correction.5,8


  1. Baran R, Haneke E, Richert B. Pincer nails: definition and surgical treatment. Dermatol Surg. 2001;27(3):261-266.
  2. Lee JI, Lee YB, Oh ST, Park HJ, Cho BK. A clinical study of 35 cases of pincer nails. Ann Dermatol. 2011;23(4):417-423. doi:10.5021/ad.2011.23.4.417
  3. Frost L. Root resection for incurvated nail. J Natl Assoc Chiropodists. 1950;40:19-28.
  4. Cornelius CE III, Shelley WB. Pincer nail syndrome. Arch Surg. 1968;96(2):321-322. doi:10.1001/archsurg.1968.01330200159034
  5. Jung DJ, Kim JH, Lee HY, Kim DC, Lee SI, Kim TY. Anatomical characteristics and surgical treatments of pincer nail deformity. Arch Plast Surg. 2015;42(2):207-213. doi:10.5999/aps.2015.42.2.207
  6. Twigg EV, Weitz NA, Scher RK, Grossman ME. Pincer nails in a patient with systemic lupus erythematosus and lupus nephritis: a case report. JAAD Case Rep. 2016;2(3):233-235. doi:10.1016/j.jdcr.2016.04.001
  7. Shilpa K, Divya G, Budamakuntla L, Eswari L. To study the outcome of three-flap technique in the management of pincer nail. J Cutan Aesthet Surg. 2019;12(1):25-30. doi:10.4103/JCAS.JCAS_140_18
  8. Azevedo THV, Neiva CLS, Consoli RV, Couto ACD, Dias AFMP, Souza EJR. Pincer nail in a lupus patient. Lupus. 2017;26(14):1562-1563. doi:10.1177/0961203317694258
  9. Yabe T. Curvature index of pincer nail. Plast Reconstr Surg Glob Open. 2013;1(7):e49. doi:10.1097/GOX.0b013e3182a9647a
  10. Mimouni D, Ben-Amitai D. Hereditary pincer nail. Cutis. 2002;69(1):51-53.
  11. Chapman RS. Overcurvature of the nails—an inherited disorder. Br J Dermatol. 1973;89(3):317-318. doi:10.1111/j.1365-2133.1973.tb02983.x
  12. Hu Y-H, Lin Y-C, Hwu W-L, Lee Y-M. Pincer nail deformity as the main manifestation of Clouston syndrome. Br J Dermatol. 2015;173(2):581-583. doi:10.1111/bjd.13703
  13. Bostanci S, Ekmekci P, Akyol A, Peksari Y, Gürgey E. Pincer nail deformity: inherited and caused by a beta-blocker. Int J Dermatol. 2004;43(4):316-318. doi:10.1111/j.1365-4632.2004.01666.x
  14. Sano H, Shionoya K, Ogawa R. Foot loading is different in people with and without pincer nails: a case control study. J Foot Ankle Res. 2015;8:43. doi:10.1186/s13047-015-0100-y
  15. Clark EG, Burns KD. Pincer nails following arteriovenous fistula creation. Kidney Int. 2015;88(4):918. doi:10.1038/ki.2015.12
  16. Failla V, Richert BJS, Nikkels AF. Pincer nails associated with pamidronate. Clin Exp Dermatol. 2011;36(3):305-306. doi:10.1111/j.1365-2230.2010.03919.x
  17. Fujita Y, Fujita T. Pincer nail deformity in a patient with amyotrophic lateral sclerosis. Neurol Int. 2014;6(4):5716. doi:10.4081/ni.2014.5716
  18. Ishikawa T, Nishizawa A, Satoh T. Acroangiodermatitis with pincer nail of the finger due to venous hypertension from hemodialysis arteriovenous shunt. Eur J Dermatol. 2018;28(2):247-248. doi:10.1684/ejd.2018.3226
  19. Jemec GBE, Kollerup G, Jensen LB, Mogensen S. Nail abnormalities in nondermatologic patients: prevalence and possible role as diagnostic aids. J Am Acad Dermatol. 1995;32(6):977-981. doi:10.1016/0190-9622(95)91335-1
  20. Kanekura T. Pincer nail deformity in a patient with Kawasaki disease. J Dermatol. 2019;46(10):e350-e351. doi:10.1111/1346-8138.14937
  21. Makino K, Ogawa Y, Kanagawa T, et al. Presence of a family history and excessive pressure on the first toe pad during walking in female subjects with pincer nails. J Dermatol. 2019;46(7):631-633. doi:10.1111/1346-8138.14931
  22. Salem A, Al Mokadem S, Attwa E, Abd El Raoof S, Ebrahim HM, Faheem KT. Nail changes in chronic renal failure patients under haemodialysis. J Eur Acad Dermatol Venereol. 2008;22(11):1326-1331. doi:10.1111/j.1468-3083.2008.02826.x
  23. Pang H-N, Lee JY-L, Tan AB-H. Pincer nails complicated by distal phalangeal osteomyelitis. J Plast Reconstr Aesthet Surg. 2009;62(2):254-257. doi:10.1016/j.bjps.2007.10.009
  24. Won J-H, Chun J-S, Park Y-H, Kim S-J, Won Y-H. Treatment of pincer nail deformity using dental correction principles. J Am Acad Dermatol. 2018;78(5):1002-1004. doi:10.1016/j.jaad.2017.08.014

NEXT: Subungual Hyperkeratosis

Subungual Hyperkeratosis

Subungual hyperkeratosis refers to the accumulation of scales under the nail plate, which is detached and uplifted.1 The nail bed often appears thickened.2,3 The condition results from excessive proliferation of keratinocytes and failure to shed off from the stratum corneum. Subungual hyperkeratosis can be localized or diffuse over the whole width of the nail.1 Typically, subungual hyperkeratosis is most prominent distally and extends proximally (Figure). Proximal subungual hyperkeratosis has rarely been reported.4 The color of the nail plate may vary from white to yellow depending on the underlying cause.2

subungual hyperkeratosis

Common causes include psoriasis, onychomycosis, and chronic eczema involving the nail bed.2,5,6 Other causes include chronic trauma to the nail bed, aging, medications (eg, venlafaxine, docetaxel, clofazimine), lichen striatus, phaeohyphomycosis caused by Bipolaris hawaiiensis, cutaneous sarcoidosis, incontinentia pigmenti, and Reiter syndrome.5,7-11

Although subungual hyperkeratosis is not specific for any disease, it may aid in the diagnosis in the presence of other symptoms and signs.


  1. Alessandrini A, Starace M, Piraccini BM. Dermoscopy in the evaluation of nail disorders. Skin Appendage Disord. 2017;3(2):70-82. doi:10.1159/000458728
  2. Perera E, Sinclair R. Diagnosis using the nail bed and hyponychium. Dermatol Clin. 2015;33(2):257-263. doi:10.1016/j.det.2014.12.006
  3. Schons KRR, Knob CF, Murussi N, Beber AAC, Neumaier W, Monticielo OA. Nail psoriasis: a review of the literature. An Bras Dermatol. 2014;89(2):312-317. doi:10.1590/abd1806-4841.20142633
  4. Romano C, Massai L. Proximal subungual hyperkeratosis of the big toe due to Microsporum gypseum. Acta Derm Venereol. 2001;81(5):371-372. doi:10.1080/000155501317140151
  5. Miura Y, Takehara K, Nakagami G, et al. Screening for tinea unguium by thermography in older adults with subungual hyperkeratosis. Geriatr Gerontol Int. 2015;15(8):991-996. doi:10.1111/ggi.12380
  6. Nagar R, Nayak CS, Deshpande S, Gadkari RP, Shastri J. Subungual hyperkeratosis nail biopsy: a better diagnostic tool for onychomycosis. Indian J Dermatol Venereol Leprol. 2012;78(5):620-624. doi:10.4103/0378-6323.100579
  7. Abimelec P, Rybojad M, Cambiaghi S, et al. Late, painful, subungual hyperkeratosis in incontinentia pigmenti. Pediatr Dermatol. 1995;12(4):340-342. doi:10.1111/j.1525-1470.1995.tb00197.x
  8. Dalle S, Becuwe C, Balme B, Thomas L. Venlafaxine-associated psoriasiform palmoplantar keratoderma and subungual hyperkeratosis. Br J Dermatol. 2006;154(5):999-1000. doi:10.1111/j.1365-2133.2006.07197.x
  9. Fujii K, Kanno Y, Ohgo N. Subungual hyperkeratosis due to sarcoidosis. Int J Dermatol. 1997;36(2):125-127. doi:10.1111/j.1365-4362.1997.tb03070.x
  10. Leposavic R, Belsito DV. Onychodystrophy and subungual hyperkeratosis due to lichen striatus. Arch Dermatol. 2002;138(8):1099-1100.
  11. Romano C, Ghilardi A, Massai L. Subungual hyperkeratosis of the big toe due to Bipolaris hawaiiensis. Acta Derm Venereol. 2004;84(6):476-477.

NEXT: Digital Mucous Cyst

Digital Mucous Cyst

Digital mucous cysts (also known as digital myxoid cysts or synovial cysts) are benign, myxoid cysts typically located on the dorsal aspect of the digits.1-5 The terms mucous and myxoid refer to the jellylike content within the cyst. The condition was first described in 1883 by Hyde as synovial lesions of the skin.6 Digital mucous cysts are most commonly seen in individuals 50 to 70 years of age.2,7 The female to male ratio is approximately 2 to 1.1,7,8 Presumably, these cysts result from degenerative changes in the synovial tissue or fibrous capsule of the joint.2,5,9

Characteristically, a digital mucous cyst presents as a slow-growing, solitary, circumscribed, translucent, skin-colored, compressible, dome-shaped, cystic nodule measuring 3 to 10 mm in diameter on the finger (Figure 1).2-5,7 The index finger and middle finger of the dominant hand are more commonly affected.1,3,4,10,11 Involvement of a toe is less common.2-4 Multiple lesions are uncommon.10,12 The cyst typically is located on the dorsal aspect of the digit between the distal interphalangeal joint and the proximal nail fold. The cyst is more common on the radial than the ulnar aspect of the finger.12-14 There is frequently an underlying osteoarthritis.15 Less commonly, the lesion is found between the proximal nail fold and the nail plate, beneath the nail matrix, or in the digital pulp.3,8,14 When the cyst is under the nail matrix, a red lunula and a longitudinal brownish band may be seen. Longitudinal grooving or depression of the nail plate, termed the “nail groove sign,” may occur because of the pressure exerted on the nail matrix (Figure 2).3,13

Digital mucous cyst fig 1
Figure 1.

Digital mucous cyst fig 2
Figure 2.

The condition is usually asymptomatic but may occasionally be accompanied by discomfort, hypersensitivity, and/or pain and decreased range of motion, especially if there is an underlying osteoarthritis or the cyst is large.1,9,15 The cyst may rupture spontaneously or when compressed to produce a mucinous or gelatinous fluid that may be clear or yellow-tinged.1,5 Other complications include cosmetic disfigurement and nail dystrophy.1,10

The prognosis is good. Watchful observation may be appropriate for asymptomatic patients. For symptomatic patients and patients who prefer treatment, simple surgical excision of the cyst is the treatment of choice. Cryotherapy, intralesional triamcinolone, and repeated puncture and drainage (“scarification”) may also work with repeated treatments.2,9,11,12


  1. Chae JB, Ohn J, Mun J-H. Dermoscopic features of digital mucous cysts: a study of 23 cases. J Dermatol. 2017;44(11):1309-1312. doi:10.1111/1346-8138.13892
  2. Jabbour S, Kechichian E, Haber R, Tomb R, Nasr M. Management of digital mucous cysts: a systematic review and treatment algorithm. Int J Dermatol. 2017;56(7):701-708. doi:10.1111/ijd.13583
  3. Leung AKC, Barankin B. Digital mucous cyst. Aperito J Dermatol. 2015;2(1):108. Accessed April 14, 2020.
  4. Li K, Barankin B. Digital mucous cysts. J Cutan Med Surg. 2010;14(5):199-206. doi:10.2310/7750.2010.09058
  5. Salerni G, González R, Alonso C. Dermatoscopic pattern of digital mucous cyst: report of three cases. Dermatol Pract Concept. 2014;4(4):65-67.
  6. Hyde JN. A Practical Treatise on Diseases of the Skin, for the Use of Students and Practitioners. Lea Brothers & Co; 1883:423.
  7. Park SE, Park EJ, Kim SS, Kim CW. Treatment of digital mucous cysts with intralesional sodium tetradecyl sulfate injection. Dermatol Surg. 2014;40(11):1249-1254. doi:10.1097/DSS.0000000000000135
  8. Hur J, Kim YS, Yeo KY, Kim JS, Yu HJ. A case of herpetiform appearance of digital mucous cysts. Ann Dermatol. 2010;22(2):194-195. doi:10.5021/ad.2010.22.2.194
  9. Kim EJ, Huh JW, Park H-J. Digital mucous cyst: a clinical-surgical study. Ann Dermatol. 2017;29(1):69-73. doi:10.5021/ad.2017.29.1.69
  10. Hwang C-Y, Huang Y-L, Liu H-N. Digital mucous cysts presenting as numerous translucent nodules in the right fifth finger. J Chin Med Assoc. 2011;74(2):102-103. doi:10.1016/j.jcma.2011.01.021
  11. Zuber TJ. Office management of digital mucous cysts. Am Fam Physician. 2001;64(12):1987-1990.
  12. Di Chiacchio NG, Fonseca Noriega L, Ocampo-Garza J, Di Chiacchio N. Digital mucous cyst: surgical closure technique based on self-grafting using skin overlying the lesion. Int J Dermatol. 2017;56(4):464-466. doi:10.1111/ijd.13527
  13. Rich P. Overview of nail disorders. UpToDate. Updated December 5, 2019. Accessed April 14, 2020.
  14. Sung JY, Roh MR. Efficacy and safety of sclerotherapy for digital mucous cysts. J Dermatolog Treat. 2014;25(5):415-418. doi:10.3109/09546634.2012.699180
  15. Yamashita Y, Nagae H, Yamato R, Sedo H, Abe Y, Hashimoto I. Proximal nail fold flap for digital mucous cyst excision. J Med Invest. 2016;63(3-4):278-280. doi:10.2152/jmi.63.278