The ectopic nail (EN) is an additional nail located in an abnormal site. It belongs to the onycho-heterotopia, a rare condition whose pathogenesis is indeterminate. This article illustrates the clinical-morphological and dermoscopic points of view, the diagnostic criteria, the possible pathogenesis, and surgical treatment of this pediatric onycho-heterotopia

Barbi, Egidio

Ferrari, Marco

Mazzarello, Vittorio

Dermatology Reports

English

PubMed

The ectopic nail (EN) is an additional nail located in an abnormal site. It belongs to the onycho-heterotopia, a rare condition whose pathogenesis is indeterminate. This article illustrates the clinical-morphological and dermoscopic points of view, the diagnostic criteria, the possible pathogenesis, and surgical treatment of this pediatric onychoheterotopia

Marco Ferrari

Vittorio Mazzarello

Egidio Barbi

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Onychoheterotopia in children

Archivio istituzionale della ricerca - Università di Trieste

[page 82]                                                          [Dermatology Reports 2021; 13:9068]Onychoheterotopia in childrenMarco Ferrari,1,2 Vittorio Mazzarello,2Egidio Barbi1,31Pediatric Department, University ofTrieste; 2Skinlab, Department ofBiomedical Sciences, University ofSassari; 3Institute for Maternal andChild Health IRCCS, Burlo Garofolo ofTrieste, ItalyAbstractThe ectopic nail (EN) is an additionalnail located in an abnormal site. It belongsto the onycho-heterotopia, a rare conditionwhose pathogenesis is indeterminate. Thisarticle illustrates the clinical-morphologicaland dermoscopic points of view, the diag-nostic criteria, the possible pathogenesis,and surgical treatment of this pediatric ony-cho-heterotopia.IntroductionEctopic nail (EN) is an additional andindependent nail located in an abnormalsite. Also known as onycho-heterotopia, itis an extremely rare condition whose patho-genesis remains undetermined.1 EN andmost of the nail diseases, which appear inthe first decade of life, are congenital; lessfrequently, EN is described as acquired orpost-traumatic. Onychoheterotopia is a sin-gle lesion involving the sole or, in most ofthe reported cases, occurring along with theregular fingernail, on the distal phalanx, andis attributed to digital malformations (e.g.,palmar nail syndrome) or bone alterations.2The appearance of the anomalous nail atdiagnosis ranges from 2 to 13 years, andfemales are more affected than males.Case ReportAn 11-year-old girl, skin phototype 3 ofFitzpatrick, was evaluated for an EN lesionon the right sole. The patient complained ofoccasional pains while walking and danc-ing. Family history was not significant forgenodermatosis or nail disorders. The lesionappeared at the age of 4 and had slowlyincreased since then. It was recently diag-nosed as a wart and treated with cryothera-py without any benefit. The clinical presentation showed cylin-drical-conical keratotic horns on admission(Figure 1). The surrounding skin wassmooth, with no signs of swelling or inflam-mation. We performed a dermoscopic anal-ysis, which revealed a surface made irregu-lar by transverse grooves at the periungualsulcus base (Figure 2). Treatment of ENconsists of its removal. EN was treatedunder local anesthesia by surgical excisionfollowed by phenol’s application on the nailmatrix. No local recurrence was observed inthe two-years follow-up.DiscussionThe onycho-heterotopia is a singlelesion that usually appears near the fingersand rarely involves the feet.3 The clinicalfeatures are dependent on the nail tissue’sanatomical site, and occasional pain may bereported.  Histopathological and ultrastruc-tural features are similar to those of a regu-lar nail with a reverse growth pattern.4Three zones constitute EN: nail matrix, nailbed, nail plate, similar onycholysis, but dif-ferently arranged compared to a standardnail.5 The EN has a matrix in the center orback, with a horizontal-vertical growth pat-tern and a distal or inverted orientation. Theneo-nail is generally conical and spatula-shaped at dermoscopic presentation, look-ing like a rudimentary fingernail with a cor-rugated surface and transverse furrows.3The right foot’s little finger is the most com-monly involved in EN, followed by the 4thdigit and the 2nd digit. Several hypothesestried to explain the origin of EN: the trau-matic inoculation of onycholysis or implan-tation of nail germ cells and their abnormalgrowth;6 the variation in the long arm ofchromosome 6 with congenital polyony-chia;7 the presence of stray germinal cells inectopic sites;8 the phenomenon of “paleote-nia” (paleo = ancient; teı´v = to verge on)meaning the appearance of a primitivesilent character, present in other animalspecies having a common phylogenetic ori-gin. The pathogenesis remains unclear; itseems most probable that ectopic nails arerelated to the alterations of particular genesresponsible for nail growth and orientation.9The EN is often confused with acquireddigital fibroma, cutaneous horn, clavus, for-eign body, split nail deformity, rudimentarypolydactyly associated with callus forma-tion and warts, and treated accordingly. Thelesion is often undiagnosed or misdiag-nosed, and cryotherapy alone often resultsin relapses. Surgical treatment should befollowed by the phenolization of the nailmatrix so that the germinal matrix is com-pletely removed and destroyed.ConclusionsThis report describes an unusual local-ization of a pediatric ectopic nail.Although this is a rare condition, its promptrecognition can avoid unnecessary treat-ments and allows appropriate surgical treat-ment without relapses.                             Dermatology Reports 2021; volume 13:9068Correspondence: Marco Ferrari, Pediatrics,University of Trieste, Trieste 34137, Italy. Tel: +39.0403785454, Fax +39.0403785452 E-mail: dr.marcoferrari@gmail.comKey words: Ectopic nail, Histopathology, Nailmorphology, Nail dysplasiasAcknowledgments: The authors thank MartinaBradaschia for the English revision of themanuscriptContributions: MF, Substantial contributionsto the study, including conceptualization/design, methodology, investigation, and for-mal analysis. Participation in writing andrevising the manuscript. VM, Substantial con-tributions to the study, including conceptual-ization/design, methodology, investigation,supervision, data curation, and formal analy-sis. Participation in writing and revising themanuscript. EB, Substantial contributions tothe study, including conceptualization/design,methodology, investigation, supervision, datacuration, and resources. Participation in writ-ing and revising the manuscript.Conflict of interest: The authors declare nopotential conflict of interest.Funding: None.Ethics approval: The study was approved bythe local ethical committee.Consent to publication: It was obtained by theresearch investigator.Please cite this article as: Ferrari M,Mazzarello V, Barbi E. Onychoheterotopia inchildren. Dermatol Rep 2021;13:9068.Received for publication: 6 January 2021.Revision received: 19 January 2021.Accepted for publication: 28 January 2021This work is licensed under a CreativeCommons Attribution-NonCommercial 4.0International License (CC BY-NC 4.0).©Copyright: the Author(s), 2021Licensee PAGEPress, Italy                                      [Dermatology Reports 2021; 13:9068]                                                         [page 83]References1. Riaz F, Rashid RM, Khachemoune A.Onychoheterotopia: pathogenesis, pres-entation, and management of ectopicnai. J Am Acad Dermatol 2011;64:161-6.2. Yadav S, Khullar G, Dogra S.Congenital onychoheterotopia involv-ing multiple toe nails. J Am PediatrMed Assoc 2013;103:445-7. 3. Oiso N, Kurokawa I, Tsuruta D, et al.The histopathological feature of the nailisthmus in an ectopic nail. Am JDermatopathol 2011;33:841-4.4. Ena P, Ena L, Ferrari M, Mazzarello V.Ectopic Foot Nails: Clinical and dermo-scopic features, treatment and outcomein 20 cases. Dermatology2015;231:298-303.5. Ena P, Enal L. Ferrari M, Mazzarello V.Double little toenails: report of 4 famil-ial cases. JAAD Case Reports2020;4,365-8.6. Park JH, Kim JH, Lee JH, et al.Onychodermis (specialized nail mes-enchyme) is present in ectopic nails. JCutan Pathol 2013;40:600-2.7. Soligo C, Muller AE. Nails and claws inprimate evolution. J Hum Evol1999;36:97-114.8. Kopera D, Soyer HP, Kerl H. Ectopiccalcaneal nail. J Am Acad Dermatol1996;35:484-5.9. Ena P, Mazzarello V, Dessy LA. Ectopicplantar nail: a report of two cases. Br JDermatol 2003;149:1071-4.                                                                                                                    Case ReportFigure 1. Clinical appearance of ectopic foot nails in an 11-year-old girl. Figure 2. Dermoscopic features of the ectopic nail.

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