Indian Dermatology Online Journal

: 2019  |  Volume : 10  |  Issue : 2  |  Page : 202--203

Subungual exostosis – Clinical, radiological, and histological findings

Pratap Chandra Das1, Shahid Hassan1, Piyush Kumar2,  
1 Consultant Dermatologist, Purnea, Bihar, India
2 Department of Dermatology, Katihar Medical College and Hospital, Bihar, India

Correspondence Address:
Piyush Kumar
Katihar Medical College, Katihar, Bihar

How to cite this article:
Das PC, Hassan S, Kumar P. Subungual exostosis – Clinical, radiological, and histological findings.Indian Dermatol Online J 2019;10:202-203

How to cite this URL:
Das PC, Hassan S, Kumar P. Subungual exostosis – Clinical, radiological, and histological findings. Indian Dermatol Online J [serial online] 2019 [cited 2021 Oct 23 ];10:202-203
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Full Text

A 35-year-old gentleman presented with a slow growing, asymptomatic swelling on the right great toe, and dystrophy of nail plate of 15 years duration. There was no history of prior trauma or chronic infection. The subungual nodule of around 2.5–3 cm in size was well-defined, bony hard, and was expanding, destroying nail plate, and normal architecture of nail unit. Overlying nail plate was dystrophic [Figure 1]. Radiographs of the foot revealed an outgrowth of trabeculated bone projecting from and in continuity with distal phalanx of great toe on the medial aspect, with intact well-defined cortical margins. No destructive changes were noted in the distal phalanx [Figure 2]. These radiological findings confirmed the diagnosis of subungual exostosis (SE). Histopathology from the nodule showed deposition of bone tissues in the mid and lower dermis without any accompanying inflammatory cells [Figure 3]a and [Figure 3]b. In addition, the dermis was remarkable for enchondral ossification [Figure 3]c. Overlying epidermis did not show any changes. Considering clinical, radiological, and histopathological findings, the case was diagnosed as SE and was referred to the Department of Orthopedics for excision.{Figure 1}{Figure 2}{Figure 3}

SE is an osteocartilaginous tumor, most commonly affects the distal phalanx of great toe and usually develops during adolescence. The etiopathogenesis is largely unknown. Trauma, infection, tumor, hereditary abnormality, or activation of a cartilaginous cyst is considered to play a role in its development. Most authors consider it as a reactive process to microtrauma; frequent localization on toes, especially great toe supports this hypothesis.[1] Recently, rearrangement in collagen genes COL12A1 (chromosome 6) and COL4A5 (chromosome X) with a specific translocation t(X;6) has been demonstrated in a number of cases, suggesting SE being a true neoplasm.[2] SE usually presents as a firm, fixed nodule with a hyperkeratotic surface at the distal end of the phalanx, under the nail plate. As it grows in size, nail plate gets lifted and detaches from the underlying nail bed. The condition follows a chronic progressive course; pain and onychodystrophy are the most common complications. Differentials include nail plate tumors like onychomatricoma; and space-occupying lesions of the nail bed like subungual verruca, carcinoma of the nail bed, keratoacanthoma, subungual epidermoid inclusions, and Koenen tumor. All these entities are radiolucent. One important clinical differential is enchondroma which presents in a similar manner, but is radiolucent and causes expansion of phalanx itself.[3] SE is treated surgically by complete marginal excision and it needs to be excised up to the normal bone tissue to prevent recurrence.[1]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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1DaCambra MP, Gupta SK, Ferri-de-Barros F. Subungual exostosis of the toes: A systematic review. Clin Orthop Relat Res 2014;472:1251-9.
2Storlazzi CT, Wozniak A, Panagopoulos I, Sciot R, Mandahl N, Mertens F, et al. Rearrangement of the COL12A1 and COL4A5 genes in subungual exostosis: Molecular cytogenetic delineation of the tumor-specific translocation t(X;6)(q13-14;q22). Int J Cancer 2006;118:1972-6.
3Kumar P, Alam G. Subungual exostosis on index finger in a child. Indian J Dermatol Venereol Leprol 2018;84:232-3.