Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2023;13(2):e2023153 1

Onychoheterotopia
Kethini Ramadas Ram Kumar1, Arunachalam Narayanan1, Sivaranjini Ramassamy1

1 Department of Dermatology and STD, JIPMER, Puducherry, India

Citation: Ram Kumar KR, Narayanan A, Ramassamy S. Onychoheterotopia. Dermatol Pract Concept. 2023;13(2):e2023153.  
DOI: https://doi.org/10.5826/dpc.1302a153

Accepted: November 18, 2022; Published: April 2023

Copyright: ©2023 Ram Kumar et al. This is an open-access article distributed under the terms of the Creative Commons 
Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted 
noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited.

Funding: None.

Competing interests: None.

Authorship: All authors have contributed significantly to this publication.

Corresponding author: Sivaranjini Ramassamy, MD, Associate Professor, Department of Dermatology and STD, JIPMER, 
Puducherry-605006 E-mail: sivaranjini11@gmail.com

Case Presentation

A 53-year-old farmer visited our outpatient clinic with an 

asymptomatic, slow-growing, hard, keratotic nail-like struc-

ture growing from the dorsal aspect of his left index finger 

(Figure 1) for 40 years following a penetrating injury. On ex-

amination, a 5 x 3 mm rectangular nail plate-like structure, 

with a smooth surface, was located 7 mm proximal to the 

proximal nail fold. Folds of skin, similar to proximal and dis-

tal nail folds of a normal nail, were seen surrounding it. The 

cuticle was not visible. Other nails were normal. No func-

tional disability was noted. Radiographic examination did-

n`t reveal any hypoplasia or thinning of the phalanx. Based 

on the above features, a diagnosis of  onychoheterotopia 

was made.

Teaching Point

Ectopic nail or onychoheterotopia is characterized by nail 

plate growth in regions other than the normal nail bed due 

to the presence of an ectopic nail matrix. It is classified into 

two types: congenital and acquired ectopic nail [1].

Although the pathogenesis is unclear, it is hypothesized 

to occur due to the presence of ectopic germ cells, an under-

lying subclinical polydactyly, or traumatic inoculation of nail 

matrix cells [2].

Figure 1. A slow-growing, hard, keratotic nail-like structure grow-

ing from the dorsal aspect of his left index finger with proximal and 

lateral nail folds.



2 Image Letter | Dermatol Pract Concept. 2023;13(2):e2023153

Diagnosis of ectopic nail is made based on its clinical 

findings and is supported by histopathological evaluation. 

Treatment includes surgical excision of the nail and its entire 

matrix to prevent recurrence followed by primary closure of 

the defect. We present this uncommon condition which has 

differential diagnosis of cutaneous horn, foreign body reac-

tions, and rudimentary polydactyly, and is likely to be missed 

by dermatologists.

References

1. Chatterjee K, Chaudhuri A, Chatterjee G.  Onychoheterotopia: 

a unique case. Indian J Dermatol. 2013;58(2):150-115.  

DOI: 10.4103/0019-5154.108064. PMID: 23716811. PMCID: 

PMC3657221.

2. Fleury CM, Nasser JS, Aivaz M, et al. Pediatric Ectopic Nail For-

mation following Fingertip Trauma: A Case Report and Litera-

ture Review. Plast Reconstr Surg Glob Open. 2020;8(12):e3291. 

DOI: 10.1097/GOX.0000000000003291. PMID: 33425603. 

PMCID: PMC7787327.