Indian Journal of Dermatology
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Table of Contents 
Year : 2013  |  Volume : 58  |  Issue : 2  |  Page : 150-151
Onychoheterotopia: A unique case

1 Department of Dermatology, Burdwan Medical College and Hospital, Burdwan, West Bengal, India
2 Consultant Surgeon, Khosbagan, Burdwan, India

Date of Web Publication5-Mar-2013

Correspondence Address:
Kingshuk Chatterjee
Department of Dermatology, Burdwan Medical College and Hospital, Burdwan, West Bengal
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0019-5154.108064

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How to cite this article:
Chatterjee K, Chaudhuri A, Chatterjee G. Onychoheterotopia: A unique case. Indian J Dermatol 2013;58:150-1

How to cite this URL:
Chatterjee K, Chaudhuri A, Chatterjee G. Onychoheterotopia: A unique case. Indian J Dermatol [serial online] 2013 [cited 2021 Oct 20];58:150-1. Available from:


Onychoheterotopia (syn: Ectopic nail) was first reported by Ohya in 1931. [1] It is defined as growth of nail tissue in any site other than the classical nail unit areas. [2] It is an extremely rare entity with about 55 published cases in the available literature, mostly from Japan, and only few from India. [3]

A 26-year-old male presented to us with a slowly growing, painless, hard projection on the inner left thumb, over the distal phalanx, following a vegetable thorn prick 8 years ago [Figure 1]. There was no sign of spontaneous regression. Neither was it present since birth nor was there any family history of a similar disorder. The patient received no earlier treatment for this disorder. On examination, there was a well-defined, shiny keratotic plaque, 2 × 3 mm in size that morphologically mimicked nail structure, with a depression over the proximal end [Figure 2]. There was no tenderness and the surrounding skin was unremarkable. Radiograph (AP and oblique view) of the left hand revealed neither any bony abnormality of the left thumb distal phalanx nor was there any connection between the abnormal structure and the underlying soft tissue or bone. There was no visible rudimentary or supernumerary structure [Figure 3]. Under ring block anesthesia, using 2% lignocaine without adrenaline, the nail-like structure was completely excised and the gap was closed with interrupted sutures. On histopathological examination, a fully developed nail unit was visualized with the nail matrix and nail bed [Figure 4]. Based on the clinical findings, corroborated with radiologic and histopathologic observations, a diagnosis of acquired onychoheterotopia was made.
Figure 1: Shiny, keratotic, nail - like tissue over the dorsal aspect of the left thumb

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Figure 2: Presence of a hard keratotic mass with a proximal depression, resembling nail fold over the dorsomedial aspect of the left thumb

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Figure 3: Radiograph (lateral and oblique view) of the left thumb

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Figure 4: Histopathology showing thick keratinous layer, overlying a squamous epithelium, conforming to nail unit (H and E, ×10)

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The exact pathogenic mechanism of onychoheterotopia still remains obscure. Most of the reported cases are congenital. Various hypotheses have been made to explain this aberration. They include:

  1. Presence of ectopic germ cells. [3]
  2. Ectopic nail tissue representing a type of teratoma.
  3. Dyskeratotic skin growing into a nail. [4]
  4. Visible portion of the nail plate of an occult polydactyly. [5]
  5. A component of other inherited syndromes like Pierre-Robin syndrome or Congenital Palmar nail syndrome. [6]

An autosomal-recessive mode of transmission has been suggested but not proved. [7],[8]

The acquired variety develops either after a single overwhelming trauma or after chronic repetitive injuries, which lead to both splitting and implantation of the germinal matrix or heterotopic inoculation of the oncocytes (nail bed cells). Such cases occur predominantly over the dorsal aspect of the hand. [2] Feily, et al. Have reported a case of congenital ectopic nails, where the medial aspects of the index fingers were affected. [9] Osseous defects may occur from the contact of the ectopic matrix with the underlying bone. [7] A keratotic squamous epithelium of mature nail unit, including a corneous nail plate and nail matrix, confirms the diagnosis histopathologically. [2],[10] Our case was unique because the non-dominant hand was involved in the uncommon site of the medial aspect of the distal phalanx of the left thumb after a single minor trauma.

   References Top

1.Tomita K, Inoue K, Ichikawa H, Shirai S. Congenital ectopic nails. Plast Reconstr Surg 1997;100:1497-9.  Back to cited text no. 1
2.Riaz F, Rashid RM, Khachemoune A. Onychoheterotopia: Pathogenesis, presentation, and management of ectopic nail. J Am Acad Dermatol 2011;64:161-6.  Back to cited text no. 2
3.Narang T, Kanwar AJ. Ectopic nail with polydactyly. J Am Acad Dermatol 2005; 53:1092-3.  Back to cited text no. 3
4.Goikoetxea X, Etxebarria I, Careaga M. Posttraumatic ectopic nail: Case report. J Hand Surg Am 2006;31:819-21.  Back to cited text no. 4
5.Mahdi S, Beardsmore J. Post-traumatic double fingernail deformity. J Hand Surg Br 1997;22:752-3.  Back to cited text no. 5
6.Ena P, Mazzarello V, Dessy LA. Ectopic plantar nail: A report of two cases. Br J Dermatol 2003;149:1071-4.  Back to cited text no. 6
7.Rajashekar M, Bhandary S, Shenoy M, Sali AR. Post traumatic ectopic nail. J Postgrad Med 2006;52:218.  Back to cited text no. 7
[PUBMED]  Medknow Journal  
8.Al-Qattan MM, Hassanain J, Hawary MB. Congenital palmar nail syndrome. J Hand Surg Br 1997;22:674-5.  Back to cited text no. 8
9.Feily A, Ayoobi A, Yaghoobi R, Kheradmand P. A case of congenital ectopic nails on the bilateral second fingers without bone deformity. Indian J Dermatol Venereol Leprol 2009;75:525-7.  Back to cited text no. 9
[PUBMED]  Medknow Journal  
10.Kopera D, Soyer HP, Kerl H. Ectopic calcaneal nail. J Am Acad Dermatol 1996;353:484-5.  Back to cited text no. 10


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]


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