Nail Disorders in Children

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1 Review Article Received: Novemer 13, 2017 Accepted: Decemer 5, 2017 Pulished online: Jnury 23, 2018 Nil Disorders in Children Michel Strce Auror Alessndrini Binc Mri Pirccini Dermtology, Deprtment of Experimentl, Dignostic nd Specilty Medicine, University of Bologn, Bologn, Itly Keywords Children Neworns Toddlers Koilonychi Trchyonychi Congenitl disorders Astrct Nil diseses in children do not ccount for significnt proportion of peditric consulttions, nd most of the time the nils re not oserved y the clinicin, overlooking their importnce. Specific exmintion of the nils is neglected, while locliztion to the nils could e n initil sign of syndrome or systemic disorder. Nil diseses in the peditric popultion differ from those in dults in terms of dignostic pproch nd mngement; some of them even re mnifested minly or exclusively in children. Peditric ptients with underlying systemic disorders re more likely to mnifest cquired disorders of the nils. Although rre, nil diseses in children re source of nxiety for the prents. Exmintion of the nils is n essentil prt of peditric physicl exmintion. A correct clinicl history nd creful exmintion help the clinicin to distinguish the different conditions nd to decide on the correct mngement of nil diseses in young ptients. A clssifiction of nil dystrophies ccording to ge is somewht ritrry nd unique clssifiction does not exist. Nil diseses in the peditric popultion cn e divided ccording to ge groups where predilection ppers in most of the cses. Moreover, certin normlities my e lifelong once cquired, ut their presenttion my e modified y ge, worsening or improving during life. This review descries mny of the nil conditions tht re seen in the peditric popultion ging from neworn to toddler, strting with physiologicl spects to etter recognize the pthologicl conditions S. Krger AG, Bsel Introduction The occurrence of nil diseses in infnts nd children is uncommon. Ethnic, socioeconomic, nd environmentl fctors influence their incidence. Most pulictions regrding nil diseses refer to single cses of rre inherited disorders. Only few ppers hve descried peditric nil ltertions, especilly in neworns [1]. Understnding nil ntomy should enle clinicin to interpret nil signs with greter clrity nd to etter understnd nd mnge nil diseses. This is especilly true with children, where the smll size of the nil mkes it more difficult to dignose nd mnge [2]. The nils of neworns (Fig. 1) re thin nd soft, nd the nil growth rte in children is similr to the vlues oserved in young dults, the fstest vlues of nil growth (1.5 mm per dy) E-Mil krger@krger.com S. Krger AG, Bsel Michel Strce Dermtology, Deprtment of Experimentl, Dignostic nd Specilty Medicine University of Bologn, V. Mssrenti 1 IT Bologn (Itly) E-Mil unio.it

2 Fig. 1., Norml fingernils of 3-dy-old child. Fig. 2. Norml fingernils () nd toenils () of 5-yer-old child. eing reched etween the ges of 10 nd 14 yers (Fig. 2). The thickness nd redth of the nil plte increse rpidly in the first two decdes of life. Peditric ptients hve unique susceptiility to nil disorders. Children re more susceptile to cteril nd virl diseses; yet, they re less likely to experience fungl infection of the nil pprtus. Although the cquired nil conditions oserved in childhood re similr to those of dults, the prevlence of severl diseses my vry in the different ge groups. Infections nd inflmmtory diseses ccount for high proportion of consulttions. Insted, hereditry or utoimmune conditions re commonly oserved nd dignosed in children. This exhustive review is orgnized into ctegories tht re sed on the ge t presenttion t which peditric ptients most frequently hve typicl mnifesttions for dignosis nd the disese mnifesttions during the different ges. The uthors lso demonstrte how nil normlities cn e useful mrker of specific systemic pthologies. Epidemiology Nil diseses my e congenitl or hereditry, nd signs re present t irth or my e cquired nd pper lter during the life of child. Nil normlities re feture of mny genodermtoses. One report suggests tht out 75% of congenitl syndromes re ssocited with nil normlities [3]. The exct prevlence of nil conditions in the peditric popultion is unknown, ut the literture estimtes vrile rte from 3 to 11% [4]. The prevlence of nil ltertions ws 11 nd 6.8% in two peditric studies of 100 nd 250 children, respectively, seen in peditric nd dermtologic deprtments [1]. The numer of reports out nil diseses in children is reltively smll, nd the epidemiologicl dt vry, ut rise in prevlence hs een demonstrted. However, only smll mount of epidemiologicl dt extrcted from few studies is currently ville for the peditric popultion [5]. 2 Strce/Alessndrini/Pirccini

3 Tle 1. Clssifiction of nil diseses in peditric ptients from irth to 5 yers of ge Age Physiologicl ltertions Pthologicl ltertions Neworns Birth Koilonychi Trnsient physiologicl onychoschizi Trumtic punctte leukonychi Pseudo-hypertrophy of the hllux Infnts 1 month to 1 yer Trnsient light-rown or ochre pigmenttion of the proximl nil fold Beu s lines of the fingernils Toddlers 1 3 yers Punctte leukonychi Pitting Cluing Nil-ptell syndrome Multiple ingrown fingernils Ectoderml dysplsis Dyskertosis congenit Epidermolysis ullos Congenitl mllignment of the hllux Congenitl hypertrophy of the lterl nil folds Verticl implnttion of the nil of the 5th toe Curved nil of the 4th toe Anonychi nd micronychi Beu s lines nd onychomdesis Preschoolers 3 5 yers Chevron or herringone nils Pchyonychi congenit Acute pronychi Blistering distl dctylitis Herpes simplex Ungul wrts Trchyonychi Nil lichen stritus Longitudinl melnonychi Clssifiction Congenitl nd hereditry nil diseses include numer of conditions in which nil normlities re present t irth or develop during infncy. In some cses, nil normlities re key fetures for the dignosis of syndromes or hereditry diseses. Nil disorders in children cn e divided into different ctegories. A wy to clssify peditric nil disorders is ccording to the ge t which they pper in most of the cses, focusing on diseses tht ffect young ptients from irth to 5 yers of life (Tle 1). Every ctegory is then divided into (1) physiologicl ltertions, representing prticulr nil fetures typicl of children tht usully dispper with ging nd do not require ny tretment, or only to ressure prents, nd (2) pthologicl conditions. The first ctegory consists of neworns, with ltertions present t irth or in the first dys of life. The second ctegory is represented y infnts from the ge of 1 month to 1 yer. Children 1 3 yers old, i.e., toddlers, represent the third ctegory, nd, finlly, the lst ctegory is chrcterized y children etween 3 nd 5 yers of ge, nmed preschoolers. Neworns: At Birth Physiologicl Altertions Koilonychi Koilonychi descries nils with trnsverse nd/or longitudinl concve nil dystrophy with centrl depression (Fig. 3). The term spoon nils descries the flttening in the middle with n everted lterl edge. It hs multiple etiologies: hereditry, cquired, or idiopthic. It is frequently idiopthic in neworns especilly on the ig toe, where it is present in 33% of cses s norml vrint nd spontneously regresses when the nil plte thickens fter the ge of 9 yers. It my e mnifesttion of inflmmtory skin diseses such s psorisis or lichen plnus, or secondry to systemic ltertions such s iron deficiency, Plummer-Vinson syndrome, nutritionl store normlities, or endocrine disorders [6]. Trnsient Physiologicl Onychoschizi Trnsient physiologicl onychoschizi is minly noted on the ig toes nd thums, with trnsverse nd lmellr splitting t the free edge in erly infncy (Fig. 4) in 28.8% of neworns [6, 7]. This pprent hypertrophy does not Clinicl Aspect of Nil Disorders in Neworns nd Toddlers 3

4 Fig. 4. Clinicl picture () nd dermoscopy () of trnsient physiologicl onychoschizi. Fig. 3. Koilonychi in nterior () nd lterl view (). need ny tretment, ecuse it is proly physiologiclly trnsitory ltertion. Trumtic Punctte Leukonychi Becuse of the smooth surfce of the nil plte in neworns, it is possile to oserve the presence of punctte leukonychi. This is true leukonychi cused y ltertions or imperfections in the proximl prt of the mtrix [8]. Apprent Hypertrophy of the Proximl nd Lterl Nil Fold: Pseudo-Hypertrophy of the Hllux This is present in 73.1% of neworns nd ccentuted y the presence of koilonychi nd tringulr shpe of the nil plte [1]. The thin nil plte nd the shpe induce minor force pushing down the lterl folds, which rect y overlpping ut with no sign of inflmmtion. Pthologicl Conditions Cluing Usully, the ngle etween the proximl nil fold nd the nil plte is nmed Loviond s ngle, nd it is greter thn 180. When there is n ltertion to this ngle, the nils re ffected y cluing, where the nil resemles clock glss with hypercurvture in the trnsversl nd longitudinl xes. Cluing my e congenitl or cquired. Acquired cluing is uncommon, nd in 80% of cses is ssocited with pulmonry diseses. Congenitl cluing cn e ssocited with crdic disorders, or more commonly lung or owel disese [9]. Sometimes, t irth, the nil curves over the tip of the digit towrds the pulp; physiologicl cluing my e seen in this ge group. Nil-Ptell Syndrome Nil-ptell syndrome is rre utosoml dominnt disorder with vrile expressivity cused y muttions in the LMX1B gene, locted in chromosome 9q34, with n incidence of pproximtely 1: 50,000, with de novo muttions ccounting for 12.5% of cses. A clinicl tetrd 4 Strce/Alessndrini/Pirccini

5 Fig. 5. Clinicl picture () nd dermoscopy () of Beu s line in neworn. of chnges to the nils, knees, nd elows, s well s the presence of ilic horns, is typicl [10]. Nil nomlies re evident t irth in 95.1% of nilptell syndrome ptients, nd re descried s micronychi or nonychi, with thin or sent pltes, incresed frgility, Beu s lines, longitudinl ridging, nd tringulr lunule, which re the most common nd pthognomonic finding. The severity of the signs is vrile, nd there is phenotypic vriility. Erly dignosis is necessry for the mngement of the disese. The chrcteristic finding regrding lunule is chrcterized y their tringulr shpe, with the horizontl sis of the tringle level with the proximl mrgin nd the point of the tringle directed towrd the distl mrgin. Nil chnges cn e seen in the fingernils, nd re commonly ilterl nd symmetricl, with their severity decresing from the 1st towrds the little finger. Ilic horns, protuernces rising from the centrl prt of the externl ilic fosse, re pthognomonic rdiologicl findings, nd re evident lso on prentl ultrsonogrphy [11]. Renl dmge with proteinuri, hemturi, hypertension, nd nephrotic syndrome [12] is the most severe compliction. Multiple Ingrown Fingernils in Neworns Multiple ingrown fingernils in neworns re possile round the 6th dy of life due to grsp reflex, s well s distl toenil emedding with normlly directed nil, due to short nd thin nil plte. During infncy, the distl phlnx hs not yet ossified, nd thus pressure to the nil plte cn cuse it to emed in the surrounding soft tissue. As the innte immune system recognizes the emedded nil plte s foreign ody cusing n inflmmtory rection, the infnt s grsp reflex cn cuse the necessry pressure to the nil plte to strt this condition. It is enign condition with spontneous regression s the reflex disppers round the 4th month of life, nd the condition does not recur [13]. It is trnsitory unless there is congenitl mllignment. Infnts: From 1 Month to 1 Yer of Age Physiologicl Altertions Trnsient Light-Brown or Ochre Pigmenttion of the Proximl Nil Fold Trnsient light-rown or ochre pigmenttion of the proximl nil fold nd dorsl digit to the interphlngel joint is more typicl of drk-skinned infnts. It is physiologicl melnic pigmenttion ppering in the first 6 months of life nd persists for few months, chrcterized y regulr reticulr pttern locted only in the periungul tissue without involvement of the cuticle or nil unit [9]. This condition is enign nd trnsitory, nd no symptoms re ssocited with it. Beu s Lines of the Fingernils Beu s lines of the fingernils pper t 4 weeks of life in 92% of neworns nd dispper with growth efore 14 weeks. This phenomenon descries single trnsverse depression of the fingernils (Fig. 5). Beu s lines result from intruterine distress or physiologicl ltertions during irth [7]. They re trnsverse nil plte Clinicl Aspect of Nil Disorders in Neworns nd Toddlers 5

6 Fig. 6. Ectoderml dysplsi. Fig. 7. Punctte leukonychi in the fingernils. surfce depressions resulting from mild trum to the proximl nil mtrix, with trnsiently reduced nil growth. Pthologicl Conditions Ectoderml Dysplsis Ectoderml dysplsis re complex group of congenitl disorders tht includes distinct conditions, chrcterized y norml development in two or more ectoderml structures (hir, nils, teeth, nd swet glnds). According to Visinoni et l. [14], moleculr sis ws identified in only 30% of cses. Nil ltertions re not specific, nd they include hypoplsi with suungul hyperkertosis in most cses (Fig. 6), or nonychi or micronychi, thinning, or onycholysis. Toddlers: From 1 to 3 Yers of Age Physiologicl Altertions Physiologicl ltertions in toddlers re typiclly due to simple trumt tht induce n inflmmtion of the nil mtrix, nd they reflect superficil ltertions to the nil plte. These events re typicl of this ge group, ecuse toddlers ply continully with their hnds. Punctte Leukonychi Children usully re ffected y true leukonychi tht occurs due to trum to the distl mtrix. In true leukonychi, the milky white discolortion is locted within the nil plte, nd results from the presence of foci of prkertotic cells within the nil plte. The presence of nuclei impirs nil plte trnsprency nd reflects light, resulting in the white color. Depending on its shpe, leukonychi cn e punctte or trnsverse. Punctte leukonychi is typicl of severl fingernils (Fig. 7). Trnsverse leukonychi is quite rre in children, nd is typiclly restricted to the 1st toenils. This vriety of true leukonychi is due to trum from shoes to thick nil plte, which trnsmits the trum to the distl nil mtrix, resulting in periodic defective kertiniztion with the production of one or more trnsverse white nds tht move distlly with nil growth [15]. Pitting Pits re smll depressions of the nil plte surfce. Depending on its size nd distriution, pitting my e dignostic of specific disese (Fig. 8). Dermoscopy of pitting is very helpful to distinguish diseses ppering with pitting, especilly in cses where pitting is the only sign (Fig. 8) [16]. Pitting is commonly seen in nil psorisis nd in nils of ptients with lopeci ret. The pits of psorisis re lrge, deep, nd irregulr in shpe, size, nd distriution, while the pits of lopeci ret re regulr in shpe, size, nd distriution. Pthologicl Conditions Dyskertosis Congenit Dyskertosis congenit is very rre hereditry disorder of telomere mintennce tht cuses short telomeres nd my demonstrte different ptterns of inheritnce [17]. Dystrophy of the nils, leukokertosis of the orl mucos, nd extensive net-like pigmenttion of the skin is the typicl trid of symptoms. Nil chnges re the first 6 Strce/Alessndrini/Pirccini

7 Fig. 8. Clinicl picture () nd dermoscopy () of pitting. Congenitl Mllignment of the Hllux In congenitl mllignment of the gret toenil, the mtrix is lterlly devited nd not prllel to the corresponding xis of the distl phlnx, which is why it produces short dystrophic nil (Fig. 9) [20]. This devition frequently cuses periungul inflmmtion, onychogryphosis, nd ltertions to the nil plte, with ridging due to trum to the position of the toenil. Spontneous improvement is possile with good nil ed ttchment nd persistence only of mlligned ppernce. When there is no improvement y the ge of 2 yers, the nil stys thick, tringulr, medilly ent, discolored, nd oys mnifesttion, ppering during erly childhood, sometimes s erly s the 1st yer of life, nd they led to splitting, dystrophy, nd shedding of nils. Multisystemic involvement (dentl, gstrointestinl, genitourinry, neurologicl, ophthlmic, pulmonry, nd skeletl) hs een descried, nd one mrrow filure cn develop in 50 90% of cses [2]. Epidermolysis Bullos Epidermolysis ullos (EB) is group of genetic disorders with n utosoml dominnt or recessive mode of inheritnce nd more thn 300 muttions in genes encoding different proteins involved minly in the structure nd function of the derml-epiderml junction [18]. A mrked mechnicl frgility of epithelil tissues is the most importnt feture, with nonscrring listering nd erosions fter minor trum due to nchoring defects etween the epidermis nd dermis, nd it hs severl, vrying phenotypes. The vrition in phenotypic expression depends on the involved structurl protein tht medites cell dherence etween the different lyers of the skin. EB is clssified y level of skin clevge (from top to ottom) into four groups: (1) EB simplex, (2) junctionl EB, (3) dystrophic EB, nd (4) Kindler syndrome. The disese cn involve the eyes, nose, ers, upper irwys, genitourinry trct, nd gstrointestinl trct. The phenotypes for every sutype rnge from reltively mild listering of the fingernils nd toenils to more generlized listering. Nil normlities usully precede skin listering. Blisters re rrely present or miniml t irth, nd they my occur t pproximtely the ge of 18 months; some individuls mnifest the disese in dolescence or erly dulthood. Fig. 9. Congenitl mllignment of the gret toenils. The nil dystrophy cn e permnent, with nonychi, progressive hyperkertosis with onychogryphosis, nil thickening, nd prrot ek nil deformity in dult life [19]. Clinicl Aspect of Nil Disorders in Neworns nd Toddlers 7

8 Fig. 10. Congenitl hypertrophy of the lterl nil folds. Fig. 11. Congenitl nonychi in 1-yer-old child. tershell-like with severe onycholysis. A surgicl pproch is recommended in severe cses [21]. Congenitl Hypertrophy of the Lterl Nil Folds The medil nd/or lterl nil folds re hypertrophic nd cover up to one-hlf of the nil prtilly or completely (Fig. 10). Congenitl hypertrophy of the lterl nil folds is present t irth or shortly therefter due to synchronism etween the growth of the nil plte nd tht of the soft tissues [4]. Possile complictions due to hypertrophy of the folds re pinful pronychi, koilonychis, nd mllignment of the sme digit. Spontneous improvement my occur over time within the 1st yer of life. If no improvement is evident fter this period, surgery is possile option to consider [21]. Verticl Implnttion of the Nil of the 5th Toe Verticl implnttion of the nil of the 5th toe is n uncommon disorder tht consists of lterl implnttion of the 5th toe mtrix. The nil virtully grows in verticl direction, nd ends ckwrds with gret discomfort especilly when socks re pulled on. In ddition, it cretes n esthetic inconvenience [7]. Keeping the nil extremely short usully suffices to solve the inconvenience of the condition, ut possile option is complete nil ltion with phenoliztion [4]. Curved Nil of the 4th Toe Curved nil of the 4th toe is mostly descried in young Jpnese ptients, where the 4th digit, usully ilterlly, is curved without ny one or soft tissue ltertion. It is congenitl condition inherited s n utosoml recessive trit [7]. No explntion is descried for this condition. It hs no clinicl significnce nd is not ssocited with ny syndrome. Although it is congenitl, usully it is noted fter irth ecuse of the deformity of hypoplsi of the distl phlnx [4]. Anonychi nd Micronychi Anonychi nd micronychi cn e isolted or prt of severl complex syndromes such s Iso-Kikuchi syndrome, ectoderml dysplsi, nd nil-ptell syndrome or in utero exposure to toxins. The term nonychi descries either prtil or complete sence of the nil (Fig. 11). It cn e congenitl nd ssocited with other deformities descriing n utosoml or recessive inheritnce. However, it cn lso e cquired fter gret event inducing the complete destruction of the ffected re, such s listers in EB [19] or inflmmtion in nil lichen plnus. The term micronychi identifies congenitl mlformtion with hypoplsi of the nil plte. It cn e secondry to exposure to tertogenic drugs in erly pregnncy or prt of syndrome [7]. 8 Strce/Alessndrini/Pirccini

9 Beu s Lines nd Onychomdesis Trum or infection, with sustntil mtrix inflmmtion or dmge, results in wve of thinned nil in the form of trnsverse groove (Beu s line) growing out t rte tht llows clcultion of the time since the episode occurred. An event within digit will limit the feture to tht digit. A generlized event, such s systemic illness, my crete groove in multiple digits. When the underlying event is gret, detchment of the nil plte from the proximl nil fold results in full-thickness trnsverse interruption of the nil plte, followed y shedding of the nil, known s onychomdesis. Drug eruptions s well s systemic infections re considered trigger fctors for the onset of onychomdesis [22]. Finger Sucking Frequently, infnts suck one finger, usully thum, even during the visit to the doctor. Thum-sucking is common childhood hit tht my increse microil exposure. Thirty-one percent of children re frequent thum-suckers t more thn 1 yer of ge [23]. The prolonged exposure of the skin of the digit to sliv induces mcertion nd irrittion, with contct dermtitis of the periungul tissue cusing cuticle dmge nd pronychi. The inflmed periungul skin displys skin mcertion crusts nd scling, nd it possily induces dmge to the nil mtrix with the presence of Beu s lines tht descrie longitudinl furrow cross the nil plte with nil growth. Another possiility is the hit of pushing ck the cuticle, which induces surfce normlities (wshord nils). One or more nds of longitudinl melnonychi cn pper due to melnocytic ctivtion fter these types of trum to the nil mtrix. Periungul wrts nd cteril pronychi re common infective complictions tht require specific locl therpy. Hnd, Foot, nd Mouth Disese One of the most studied infections is hnd, foot, nd mouth disese, where the reltionship with onychomdesis is well descried [24]. Onychomdesis of severl or ll nils occurs 1 2 months fter the cute infection (Fig. 12). This is common peditric virl infection with vesiculr eruptions tht involve the plms, soles, nd orl cvity. Nil shedding strts to present without pin or inflmmtion until complete seprtion of the nil plte in trnsversl ridging of severl or ll fingernils nd toenils. This condition is reversile nd self-limited, ut the exct mechnism y which the Fig. 12. Onychomdesis in the fingernils due to hnd, foot, nd mouth disese. illness induces this dmge to the mtrix is unknown. No specific tretment is required, only to ressure the fmily. Preschoolers: From 3 to 5 Yers of Age Physiologicl Altertions Chevron or Herringone Nils In chevron or herringone nils, the nil plte surfce shows olique nd longitudinl digonl ridges converging towrds the center of the nil plte t the distl prt, descriing centrl spine with the ppernce of V- shpe or chevron. It ppers etween the ge of 5 nd 7 yers nd disppers in erly dulthood [25]. It ffects severl or ll fingernils, with n undetermined etiology [4]. Pthologicl Conditions Pchyonychi Congenit Pchyonychi congenit is n uncommon genodermtosis chrcterized y defective kertiniztion. Clinicl fetures include hypertrophic nil dystrophy, pinful plmoplntr listers, cysts, folliculr hyperkertosis, nd orl leukokertosis. The Interntionl Pchyonychi Congenit Reserch Registry (IPCRR) hs identified more thn 100 muttions [26]. Its inheritnce is utosoml dominnt, ut spordic nd utosoml recessive cses re reported [27]. There re two types of pchyonychi congenit: type 1, lso known s Jdssohn-Lewndowsky syndrome, nd type 2, lso known s Jckson-Lwler syndrome; they re linked to muttions in genes encoding five differentition-specific kertins: 6A, 6B, 6C, 16, nd 17. Clinicl Aspect of Nil Disorders in Neworns nd Toddlers 9

10 Fig. 13. Acute pronychi due to cteril injury. Bcteril Diseses Blistering Distl Dctylitis Blistering distl dctylitis is rre, loclized infection y grm-positive cteri tht most commonly ffects children. It is chrcterized y development of n crl ovl fluid-filled ull, mm in dimeter, usully on one finger pd [31]. The ge group ffected is 2 16 yers old. The ull cn evolve into erosions over the course of severl dys. The custive orgnism is group A β-hemolytic Streptococcus; less commonly, Stphylococcus ureus nd Stphylococcus epidermis re isolted. A differentil dignosis includes herpetic whitlow, EB, ullous impetigo, nd friction listers. Culture is necessry for differentil dignosis nd to identify the orgnism for the choice of tretment. The optiml tretment for these ptients is incision nd dringe, wrm compresses, nd orl ntiiotics [4]. Erly development of nil thickening with n incresed curvture due to nil ed hyperkertosis, ssocited with plmoplntr kertoderm, is the clinicl mnifesttion. Nil nd skin chnges re present t irth in only 50% of cses, ut y 5 yers, they re seen in more thn 75% of children. By the ge of 10 yers, pin cn e present s symptom, which gretly impirs qulity of life [28]. Acute Pronychi Cuticle loss mkes it more difficult for the proximl nil fold to ply its protective role nd mens tht the first sel is roken. Acute pronychi is pinful cteril or virl infection resulting from rek in the skin, prick of thorn, or splinter (Fig. 13). The most likely pthogens include cteri, such s Stphylococcus ureus nd β-hemolytic Streptococcus [29]. After the infection, n inflmmtory response ensues in the digit, with resultnt swelling, erythem, tenderness, nd secondry pus formtion [4]. As the nil mtrix in children is prticulrly frgile, even mild cute pronychi my induce permnent nil dystrophy. Chronic mnipultion, inflmmtion, or infection cn result in chronic sence of the cuticle, i.e., chronic pronychi, often presenting with cute flres over long period of time [30]. Possile therpies include compression primrily nd locl mediction with ntiiotic crem secondrily. In cse of strong rection, possile dringe is dvised nd specific systemic ntiiotic or ntivirl therpy hs to e strted. Virl Diseses Herpes Simplex Herpes simplex infection, oth primry nd secondry, my loclize to one finger. Secondry fingernil herpes simplex virus infections re presenting s recurrent pronychi in the sme digit, chrcterized y grouped vesicles locted on the lterl nil fold ccompnied with pin, swelling, nd erythem. Rrely, nil ed loction my occur, with pinful lterl onycholysis nd suungul hemorrhge. The dignosis is confirmed with Tznck smer or virl culture, nd specific ntivirl therpy is recommended, usully with locl ppliction. Ungul Wrts Virl wrts re enign infectious lesions due to humn ppillomvirus strins of vrious types. They re very common in children over 6 yers of ge, fcilitted y nil iting. Cliniclly, wrts strt s smll round hyperkertotic msses with rough surfce; then they grow, reching size of up to mm nd induce fissuring with possile pin. They re usully locted in the proximl nil folds ut my lso develop under the nil plte with onycholysis. It is recommended tht the onycholytic prt e cut when it is present nd the wrts e treted with kertolytic crem such s ure or slicylic cid. Trchyonychi Trchyonychi, or twenty-nil dystrophy (TND), mens nil roughness. This is enign inflmmtory nil condition of the proximl nil mtrix. It cn e present t ny ge, ut the men ge t ppernce is 2.7 yers (rnge 2 7) [32]. Its incidence in the peditric popultion is un- 10 Strce/Alessndrini/Pirccini

11 Fig. 14. Trchyonychi of ll digits (twenty-nil dystrophy). known. Cliniclly, it cn e divided into two min groups: idiopthic TND nd TND ssocited with other dermtologicl diseses including lopeci ret, lichen plnus, eczem, nd psorisis. Trchyonychi is not distinctive disese ut only the clinicl result of disorders tht involve the nil mtrix [22]. In the sence of nmnestic or clinicl dt tht suggest its pthology, it is impossile to detect disese tht is cusing the trchyonychi without histopthologicl study [32]. Nil iopsy is not recommended for dignosis, due to the enignity of the disese nd good prognosis. TND cn ffect one nil or ll nils (Fig. 14). The ffected nils show diffuse roughness with longitudinl nd regulr fissuring, nd re usully opque with sndpper ppernce. Nil thinning with koilonychi nd cuticle hyperkertosis my e present. TND will show spontneous improvement over time. Nil Lichen Stritus Nil lichen stritus is rre nd lmost exclusively seen in children. Cliniclly, one nil is involved, which shows lichenoid normlities with longitudinl ridging restricted to its medil or lterl portion (Fig. 15). It usully continues with liner skin lesions chrcterized y ppules or verrucous scles long Blschko s lines. Nil involvement ppers few weeks fter the initil skin lesions. Nil chnges my occsionlly e the only clin- Fig. 15. Clinicl picture () nd dermoscopy () of nil lichen stritus of the 1st digit. Clinicl Aspect of Nil Disorders in Neworns nd Toddlers 11

12 Longitudinl Melnonychi Longitudinl melnonychi is rown-lck pigmented nd from the proximl to the distl nil plte due to the presence of melnin within the nil plte. The pigmenttion is produced y ctivtion or prolifertion of quiescent melnocytes. Unlike in dults, the principl cuse of longitudinl melnonychi in children is nil mtrix nevi, nd it my e present t irth or my develop t 2 4 yers of ge (Fig. 16). In children, 75% of cses of longitudinl melnonychi re due to enign melnocytic hyperplsi, minly junctionl nevi, nd 25% re due to melnocytic ctivtion [34]. The clinicl nd dermoscopic prmeters used for dults re not vlid for children (Fig. 16) [35]. Nil melnom in children is extremely rre, nd exceptionl in Cucsins [36]. A clinicl nd dermoscopic sign tht suggests melnom in children is rpid evolution in growth nd color, which requires surgicl excision. Conclusion Fig. 16. Clinicl picture () nd dermoscopy () of longitudinl melnonychi due to nil mtrix nevus. icl sign, nd they re typiclly limited to one portion of the nil nd include findings such s longitudinl fissuring, onycholysis, nd distl splitting [33]. The condition is symptomtic nd self-limiting nd should e suspected when child presents lichen plnus-like normlities in single nil. Locl steroids re suggested s tretment. Nils of neworns re thin nd soft, nd they frequently present with physiologicl ltertions tht re not necessry to tret ut only need wit-nd-see pproch nd ressurnce of the prents. Oviously, follow-up of ptients is importnt to e sure tht these physiologicl conditions do not ecome pthologicl conditions tht require therpy. Furthermore, severl conditions my led to dystrophy of the nils, including cquired conditions such s trum, trchyonychi, or lichen stritus nd congenitl disorders. Hereditry or utoimmune conditions re commonly oserved nd dignosed in children. Rrely, nil signs re the first mnifesttion of genetic disorder, nd in this cse it is usully ssocited with other skin or mucosl involvement. It is importnt to highlight the importnce of nil exmintion in children in order to perform erly dignoses nd to identify nd tret complictions. A correct clinicl history nd creful exmintion help the clinicin to distinguish etween different conditions nd to decide on the correct mngement of nil diseses in young ptients. The chnges re influenced y hits nd environmentl fctors, which gin re influenced y the ge of the ptient. This review provided comprehensive review of prevlent nil diseses in peditric ptient cohort, especilly from irth to preschool ge. Disclosure Sttement The uthors declre no conflict of interest. The uthors declre they hd no funding sources supporting this work. References 1 Chinzzo M, Lorette G, Brn R, Finon A, Sli É, Mruni A: Nil fetures in helthy term neworns: single-centre oservtionl study of 52 cses. J Eur Acd Dermtol Venereol 2017; 31: de Berker D: Nil ntomy. Clin Dermtol 2013; 31: Strce/Alessndrini/Pirccini

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