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 Editor: Luc Thomas

 Author(s): Luc Thomas     ·  Amélie Boespflug
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Author(s) Luc Thomas · Amélie Boespflug
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Status update June 25, 2018
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Subungual exostosisThis glossary term has not yet been described. (SE) is an isolated acquired slow-growing subungual benign osteo-chondral outgrowth of the dorsal side of the distal phalanx of toes and fingers that is considered by some authors to be a variant of an osteochondroma [1]. In rare cases this outgrowth can be peri-ungual[2].

Subungual exostosis is uncommon even though it is probably underreported[2]. It commonly affects young adults of both genders and is mostly localized on the first right hallux[2]. Reactive metaplasia is believed to be caused by either an acute significant traumaThis glossary term has not yet been described. or to minor repeated chronic trauma, and chronic infectionThis glossary term has not yet been described. [2].

Clinically it appears like an asymptomatic or painful subungual or peri-ungual nodule that uplifts the nail and causes nail dystrophy and onycholysis[2]. Due to its unspecific clinical presentationThis glossary term has not yet been described., accurate diagnosisis the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines with variations in the use of logic, analytics, and experience to determine "cause and effect". In systems engineering and computer science, it is typically used to determine the causes of symptoms, mitigations, and solutions is often delayed with an average time to diagnosis of 15 months[3].

Dermoscopically, vascular ectasia is the most frequent finding, followed by hyperkeratosis, onycholysis and ulcerationThis glossary term has not yet been described.. Subungual hyperkeratosis presents itself dermoscopically like a well delimited yellow spot that becomes more visible when pressure is applied by using the dermoscope[4].
Subungual Exostosis.jpg Subungual Exostosis 2.jpg

Differential diagnosis include : subungual wartsThis glossary term has not yet been described.[5], squamous cell carcinomaThis glossary term has not yet been described., amelanotic subungual melanomaThis glossary term has not yet been described.[6], subungual keratoacanthomaThis glossary term has not yet been described., acquired fibrokeratoma, pyogenic granulomaThis glossary term has not yet been described., onychomatricomaThis glossary term has not yet been described. and other uncommon subungual nail tumors and bone sarcomas.

The diagnosis is made by performing an X-ray examination that reveals a bony overgrowth. Surgical exploration with total or partial avulsion of the nail and resection of the overgrowth with histological evaluation confirms and treats subungual exostosis[7]. HistopathologyThis glossary term has not yet been described. typically reveals mature trabecular bone surrounded by a fibrocartilage cap[8]. Incomplete resections expose to the risk of local recurrences [9][10].

Xray of an ungueal exostosis
Per operative aspect of an exostosis

ReferencesThis is material contained in a footnote or bibliography holding further information.
  1. Russell JD, Nance K, Nunley JR, Maher IA. Subungual exostosis. Cutis 2016;98:128–9.
  2. DaCambra MP, Gupta SK, Ferri-de-Barros F. Subungual exostosis of the toes: a systematic review. Clinical Orthopaedics and Related Research 2014;472:1251–9.
  3. Piccolo V, Argenziano G, Alessandrini AM, Russo T, Starace M, Piraccini BM. DermoscopyThe examination of [skin lesions] with a 'dermatoscope'. This traditionally consists of a magnifier (typically x10), a non-polarised light source, a transparent plate and a liquid medium between the instrument and the skin, and allows inspection of skin lesions unobstructed by skin surface reflections. Modern dermatoscopes dispense with the use of liquid medium and instead use polarised light to cancel out skin surface reflections. of Subungual ExostosisThis glossary term has not yet been described. A Retrospective Study of 10 Patients Dermatology 2017;233:80–5
  4. Thomas L, Vaudaine M, Wortsman X, Jemec G, Drapé J. Imaging the nail unit. In: Thomas L, Baran R, editors. Baran and Dawber’s Diseases of the NailsThis glossary term has not yet been described. and Their ManagementThis glossary term has not yet been described.,. 4rth ed., London: Wiley Blackwell; 2012, p. 111–82.
  5. Daragad M, Srinivas S, Varghese J. Exostosis masquerading as a subungual wart. Indian Dermatology OnlineOnline means that something is available over, or delivered from, the internet. Journal 2014;5:92.
  6. Velanovich V. Subungual pigmented lesion caused by a bone spur: a mimic of a subungual melanoma. Military Medicine 1994;159:663.
  7. Basar H, Bal E, Inanmaz M, Basar B, Köse K. Protruded and nonprotruded subungual exostosis: Differences in surgical approach. Indian Journal of Orthopaedics 2014;48:49.
  8. Russell JD, Nance K, Nunley JR, Maher IA. Subungual exostosis. Cutis 2016;98:128–9.
  9. Wollina U, Baran R, Schönlebe J. Dystrophy of the Great Toenail by Subungual Exostosis and Hyperostosis: Three Case Reports with Different Clinical Presentations. Skin Appendage Disorders 2016;1:213–6.
  10. Malkoc M, Korkmaz O, Keskinbora M, Seker A, Oltulu I, Bulbul AM, et al. Surgical treatment of nail bed subungual exostosis. Singapore Medical Journal 2016;57:630–3.