Vertically growing ectopic nail A (i4-yeai-old Japaticse woman with an ectopic nail at the ])almar tip of the left middle finger is reported. Interestingly, the nail grew \fi tically to a line horizontal to the surface epidermis. Atyi^ically, il appeared at 60 years of age with no pricM' injury or Iratima to exjjlaiti inoculation of a natl tnattix itito the regtotial skin. Roeiitgeuographicall), there were no abnormal findings svtch as \-shaped bifurcation ofthe distal phalanx ofthe aflected finger. I here ate conllic ting o|)mions concerning whether or not a j^roximal nail fold is critical fbr the nail to grow outward instead of upward. Although the present case had a wide proximal nail lofd, it did not seem to ]jlay its role of compressing and assisting the nail plate to grow outward. Hence, it may be that the absence of a |)roper nail bed, rather than the absence of a ]5roxiiiial nail fold, promotes u|)warcl growth of a u.iil plate instead ol outwatcl growth. Kalo N. YetticalK' growing ectopic nail. J Cutan Pathol 1992: 19; 44,5-147.
Ectopic nail (onychoheterotopia) is a rare disorder of nail organs. Although the most frequent fyjK" is caused by inoculation of nail matrix by injury or trauma (I), spontaneous (ypes, including congenital ectoj:)ic nails, have l)een reported (2—4). A case c:ir a la(e-onset, spontaneous, vertically growing ectcjpic nail is jjresented below, and the origin of s]:)oiitaneous ectoyjic nails is discussed.
Naoko Kato Department of Dermatology. Otaru City General Hospital, Japan
Naoko Kato, Department of Dermatology, OtartJ City General Hospital, 2 - 1 , Wakan:iatsu 1choume, Otaru, 047, Japan Accepted February 24, 1992
ing downward into the dermal tissue. The features of these stratified squamous layers were character-
Case report A 64-year-old Jaiaancse woman presented with a hard, keratotic, asymptomatic, spiky horn at the palmar tip of the left middle finger which had repeatedly grown after ctitting, as with ordinary nails (Fig. 1). I he |)atieiit first noticed the horn approximately 5 years |)ie\'iotisly. She did not remember any injury or trauma to (he regional skin which might have inoculated nail matrix. The patient's medical history was remarkable for a brain tumor treated sttrgically 10 years previously, ever since which she had been hcmiplegic on the left side. Histological examination revealed faintly eosinophilic, regularly stratified, (hick, keratinous layers (an ectopie nail plate) in the center of a cul-de-sac composed of sc|tianious epithelium (Fig. 2). 'Fhe c-ctopic tiail stood almost vertical to a line horizontal to the surface epidermis; precisely speaking, the angle was 70°. Under the ectopic nail plate, there were .stratified squamous layers without definite granular layers. I hc-y exhibited root-like projections extend-
l''ig. I. Ml topic nail appears as a hard, kciatoti(\ asymptomatic, spiky horn on the palmar tip of left middle linger.
445
Kato rows). Under the nail matrix, there was well-demarcated, relatively thick, dermal collagenous tissue with many small vessels. After surgical resection, there was no recurrence of the ectopic nail. In the roentgenograjih taken following surgical resection, there were uo abnormal findings such as Y-shaped bifurcation at the distal phalanx of left middle linger, although severe osteoporotic disuse atro|:)hy ofthe left hand was observed.
Discussion
Fig. 2. Faintly eo.sinophilic, rcgulaily stiatified, thick, keratinous layers, an ectopic nail plate, i.s standing almost vertically in the eenter of a (iil-de-sac composed of squamous epithelium.
istic of a nail matrix. In c:ontrast, the squamous epithelium on the lateral wall of a cul-de-sac was composed of deeply eosinophilic, thick, keratinous layers, analogous to the cuticle of a proximal nail fold. This epithelium displayed several distinct granular layers, such that the turning points between the nail matrix and proximal nail fold-like epidermis could be clearly identified (Fig. 3, ar-
Nail organs are epidermal ai)pendages derived Iroin ectoderm. They are comprised of several epidermal components, i.e., a nail plate, matrix, nail bed, proximal nail fold (eponychium), and hyponychiuni (1). The nail matrix and nail bed are generally believed to keratinize without granular layers (1, 5), since no keratohyalin granules are observed in the uppermost layers of the keratcjgenous zone of these squamous layers when hematoxylin-eosin stained sections are examined under the light microscope. However, the proximal nail fold and hyponycliium are known tcj keratinize with granular layers. Under the electron microscope, Hashimoto et al. (6) demonstrated spherical keratohyalin granules, and Aoki & Suzuki (3) found cytoplasmic desmosomes in the squamous layers just beneath the nail plate. The present case featured an extraordinarily shajjed ectopic nail, i.e., a spiky horn growing vertically, 70° to a line horizontal to the surface e])idermis at the palmar tip of left middle finger. Histologically, it exhibited the characteristic features of a nail, i.e., a nail plate which did not stain with hematoxylin, a nail matrix with root-like |)rojections of
Fig. a. 1 he lurtiing points between
t h e iiail
matrix
and proximal nail fold-like epiderinis are indicated by arrows.
446
Ectopic nail
epidermal rete ridges but without granular layers, and a proximal nail fold-like epidermis with granular layers and cuticular keratin layers. Some ofthe nuclei in the uyjpermost layers of the keratogenous zone of the nail matrix stained darker and were larger, probably because ofthe presence of electrondense material in the cytoplasm of these cells. On the other hand, the nail lacked a projM-r nail bed. Fhe nail plate was surrounded by a j^roximal nail fold-like epidc-rmis circumlerentially, and consequently, the entire lesion formed a cup-shaped culde-sac with a central horn. The central horn, i.e., the vertical nail |)late, consisted of stratified stratum corncum containing fewer cells in the up]K'r layets, so that the top ofthe nail plate had a spike-like tip. A similar vertically growing, cctoj^ic nail was reported by Kikuchi et al. (7) in a 55-yeai-old Japanese woman. Although its histological features were almost identical to those in the present case (except fbr the absence of both the lower layers ofthe nail matrix and dermal tisstie in their specimen), the dilTerenccs between the two cases were onset and site. Fhe former was probably present at birth and was located on the ulnar aspect of the left middle finger. With only rare exceptions (8), ectopic nails have been reported to be ]3r(;sent from birth (9, 10) except in cases of ectopic nails after inoculation of a nail matrix by injury or trauma. Almost all of these ectopic nails have been observed distal to the distal inter|Dhalangeal joint, which is closest to the position of normal nail matrix. Some have also involved bony abnormalities of tlje affected sites (9, 10) as in nail abnormalities (11) such as Iso-Kikuchi syndrome (12). Although the origin ofthe late-onset, spontaneous ectopic nail in the present case is unknown, several features described above suggest a hamartomatous rest or a teratoma as its origin, as suggested in the past (4, 13). Ordinary nails grow out instead of up. Conflicting opinions concerning this phenomenon have been discussed by Kligman (14, 15) and Baran (HJ) and focused on whether or not a proximal nail fold is critical for the nail to grow outward instead of upward. Although the |)resent patient had a proximal nail fold, even if the angle between proximal nail fold and a nail plate was wider than the usual nar-
row angle, it did not seem to play its role of compressing and assisting the nail plate to grow outward. As there was no proper nail bed, it may be that the absence of a nail bed, rather than the absence of a proximal nail fbld, promotes upward grcnvth of a nail plate instead of outward growth. References 1. Norton LA, Zaias N. Diseases of Nails, ln: Demis DJ, ed. Glinicaf Dermatology. Philadelphia: J B Lip|:)incott, 198.'): Sec 3-0, 3 - 1 . 2. Kikuchi I, Ono f, Ogata K. l',cto|)ic nail. Gase reports. Plast Reconst Surgery I97H: 61: 781. !i. .Aoki K, Stiznki H. Ihe morphology and hardness ofthe nail in two eases of congenital onychoheterotopia. Br J Dermatol 1984: 110: 717. 4. Katayama 1, Maeda M, Nishioka K. (a)ngenital ectopic nail ofthe liftli finger. B r j Dermatol 1981: 111: 231. .•). Dawber RPR, Baran R. Fhe nails. In: Rook A, Wilkinson DS, lObling l.JG, C^hainpion RM, Burton )L, eds. lextbook of Dermatology. Oxford: BlaVkwell Scientitie, 1986: 2039. (). Hashimoto K, (Jross BG, Nelson R. Le\'er WF. 'fhe iiltiastrtieture ofthe skin of human embryos. 111. 'Phe formation ofthe nail in It)-I8 weeks old embryos. J lincst Dernuitol 1966: 47: 205. 7. Kikuchi 1, Ogata K, Idemori M. X'ertically growing ectopic nail, j Am .Acad Dermalol 1984: 10: 114. H. Kawakanii M. l'',ctopi(- nail, llihuka no Rinsho 1983: 25: 1 I:") I (in Japanese). 9. Kalisnian M, Kleitiert 111'.. /\ circuu\ferential liua;eruiv\l. Fingernail on the palmar aspect ofthe linger. J Hand Siirg 1983: 8: .58. 10. f ligashi N. A case of congenital ectopic nail. Hiliii 1981: 26: U)13 (ill Japanese). 11. felfer NR, Bartli j H , Dawber RPR. (Congenital and hetc-ditary nail dystrophies — an embiyological approach to classification. Glin Fxp Detniatof 1988: 13: 160. 12. Kikiicbi 1, I Iorika\\a S, .Amano V. Gongenital onychodysplasia ofthe index fmgers. .Arch Dc-rmatol 1971: 110: 743. 1!!. SiKcrman RA. Pcdiatric disease. In: Sc4ier RK, Daniel ('R, eds. Nails: 4'herapy, Diagnosis, Surgery. Philadeljihia: WB Saunders, 1990: 82. M. Kligman AM. Why do nails grow out instead of up:' .Nreb Detmatol 1961: 84: 313. LS. Kligman .AM. Resi>onse. J Am Aead Dermatol 1981: 1: 83. Hi. Baran R. Nail growth direction revisited. Why do nails grow out instead of up? J .Am .Aead Dermatol 1981: 4: 78.
447
Ectopic nail (onychoheterotopia) is a rare disorder of nail organs. Although the most frequent fyjK" is caused by inoculation of nail matrix by injury or trauma (I), spontaneous (ypes, including congenital ectoj:)ic nails, have l)een reported (2—4). A case c:ir a la(e-onset, spontaneous, vertically growing ectcjpic nail is jjresented below, and the origin of s]:)oiitaneous ectoyjic nails is discussed.
Naoko Kato Department of Dermatology. Otaru City General Hospital, Japan
Naoko Kato, Department of Dermatology, OtartJ City General Hospital, 2 - 1 , Wakan:iatsu 1choume, Otaru, 047, Japan Accepted February 24, 1992
ing downward into the dermal tissue. The features of these stratified squamous layers were character-
Case report A 64-year-old Jaiaancse woman presented with a hard, keratotic, asymptomatic, spiky horn at the palmar tip of the left middle finger which had repeatedly grown after ctitting, as with ordinary nails (Fig. 1). I he |)atieiit first noticed the horn approximately 5 years |)ie\'iotisly. She did not remember any injury or trauma to (he regional skin which might have inoculated nail matrix. The patient's medical history was remarkable for a brain tumor treated sttrgically 10 years previously, ever since which she had been hcmiplegic on the left side. Histological examination revealed faintly eosinophilic, regularly stratified, (hick, keratinous layers (an ectopie nail plate) in the center of a cul-de-sac composed of sc|tianious epithelium (Fig. 2). 'Fhe c-ctopic tiail stood almost vertical to a line horizontal to the surface epidermis; precisely speaking, the angle was 70°. Under the ectopic nail plate, there were .stratified squamous layers without definite granular layers. I hc-y exhibited root-like projections extend-
l''ig. I. Ml topic nail appears as a hard, kciatoti(\ asymptomatic, spiky horn on the palmar tip of left middle linger.
445
Kato rows). Under the nail matrix, there was well-demarcated, relatively thick, dermal collagenous tissue with many small vessels. After surgical resection, there was no recurrence of the ectopic nail. In the roentgenograjih taken following surgical resection, there were uo abnormal findings such as Y-shaped bifurcation at the distal phalanx of left middle linger, although severe osteoporotic disuse atro|:)hy ofthe left hand was observed.
Discussion
Fig. 2. Faintly eo.sinophilic, rcgulaily stiatified, thick, keratinous layers, an ectopic nail plate, i.s standing almost vertically in the eenter of a (iil-de-sac composed of squamous epithelium.
istic of a nail matrix. In c:ontrast, the squamous epithelium on the lateral wall of a cul-de-sac was composed of deeply eosinophilic, thick, keratinous layers, analogous to the cuticle of a proximal nail fold. This epithelium displayed several distinct granular layers, such that the turning points between the nail matrix and proximal nail fold-like epidermis could be clearly identified (Fig. 3, ar-
Nail organs are epidermal ai)pendages derived Iroin ectoderm. They are comprised of several epidermal components, i.e., a nail plate, matrix, nail bed, proximal nail fold (eponychium), and hyponychiuni (1). The nail matrix and nail bed are generally believed to keratinize without granular layers (1, 5), since no keratohyalin granules are observed in the uppermost layers of the keratcjgenous zone of these squamous layers when hematoxylin-eosin stained sections are examined under the light microscope. However, the proximal nail fold and hyponycliium are known tcj keratinize with granular layers. Under the electron microscope, Hashimoto et al. (6) demonstrated spherical keratohyalin granules, and Aoki & Suzuki (3) found cytoplasmic desmosomes in the squamous layers just beneath the nail plate. The present case featured an extraordinarily shajjed ectopic nail, i.e., a spiky horn growing vertically, 70° to a line horizontal to the surface e])idermis at the palmar tip of left middle finger. Histologically, it exhibited the characteristic features of a nail, i.e., a nail plate which did not stain with hematoxylin, a nail matrix with root-like |)rojections of
Fig. a. 1 he lurtiing points between
t h e iiail
matrix
and proximal nail fold-like epiderinis are indicated by arrows.
446
Ectopic nail
epidermal rete ridges but without granular layers, and a proximal nail fold-like epidermis with granular layers and cuticular keratin layers. Some ofthe nuclei in the uyjpermost layers of the keratogenous zone of the nail matrix stained darker and were larger, probably because ofthe presence of electrondense material in the cytoplasm of these cells. On the other hand, the nail lacked a projM-r nail bed. Fhe nail plate was surrounded by a j^roximal nail fold-like epidc-rmis circumlerentially, and consequently, the entire lesion formed a cup-shaped culde-sac with a central horn. The central horn, i.e., the vertical nail |)late, consisted of stratified stratum corncum containing fewer cells in the up]K'r layets, so that the top ofthe nail plate had a spike-like tip. A similar vertically growing, cctoj^ic nail was reported by Kikuchi et al. (7) in a 55-yeai-old Japanese woman. Although its histological features were almost identical to those in the present case (except fbr the absence of both the lower layers ofthe nail matrix and dermal tisstie in their specimen), the dilTerenccs between the two cases were onset and site. Fhe former was probably present at birth and was located on the ulnar aspect of the left middle finger. With only rare exceptions (8), ectopic nails have been reported to be ]3r(;sent from birth (9, 10) except in cases of ectopic nails after inoculation of a nail matrix by injury or trauma. Almost all of these ectopic nails have been observed distal to the distal inter|Dhalangeal joint, which is closest to the position of normal nail matrix. Some have also involved bony abnormalities of tlje affected sites (9, 10) as in nail abnormalities (11) such as Iso-Kikuchi syndrome (12). Although the origin ofthe late-onset, spontaneous ectopic nail in the present case is unknown, several features described above suggest a hamartomatous rest or a teratoma as its origin, as suggested in the past (4, 13). Ordinary nails grow out instead of up. Conflicting opinions concerning this phenomenon have been discussed by Kligman (14, 15) and Baran (HJ) and focused on whether or not a proximal nail fold is critical for the nail to grow outward instead of upward. Although the |)resent patient had a proximal nail fold, even if the angle between proximal nail fold and a nail plate was wider than the usual nar-
row angle, it did not seem to play its role of compressing and assisting the nail plate to grow outward. As there was no proper nail bed, it may be that the absence of a nail bed, rather than the absence of a proximal nail fbld, promotes upward grcnvth of a nail plate instead of outward growth. References 1. Norton LA, Zaias N. Diseases of Nails, ln: Demis DJ, ed. Glinicaf Dermatology. Philadelphia: J B Lip|:)incott, 198.'): Sec 3-0, 3 - 1 . 2. Kikuchi I, Ono f, Ogata K. l',cto|)ic nail. Gase reports. Plast Reconst Surgery I97H: 61: 781. !i. .Aoki K, Stiznki H. Ihe morphology and hardness ofthe nail in two eases of congenital onychoheterotopia. Br J Dermatol 1984: 110: 717. 4. Katayama 1, Maeda M, Nishioka K. (a)ngenital ectopic nail ofthe liftli finger. B r j Dermatol 1981: 111: 231. .•). Dawber RPR, Baran R. Fhe nails. In: Rook A, Wilkinson DS, lObling l.JG, C^hainpion RM, Burton )L, eds. lextbook of Dermatology. Oxford: BlaVkwell Scientitie, 1986: 2039. (). Hashimoto K, (Jross BG, Nelson R. Le\'er WF. 'fhe iiltiastrtieture ofthe skin of human embryos. 111. 'Phe formation ofthe nail in It)-I8 weeks old embryos. J lincst Dernuitol 1966: 47: 205. 7. Kikuchi 1, Ogata K, Idemori M. X'ertically growing ectopic nail, j Am .Acad Dermalol 1984: 10: 114. H. Kawakanii M. l'',ctopi(- nail, llihuka no Rinsho 1983: 25: 1 I:") I (in Japanese). 9. Kalisnian M, Kleitiert 111'.. /\ circuu\ferential liua;eruiv\l. Fingernail on the palmar aspect ofthe linger. J Hand Siirg 1983: 8: .58. 10. f ligashi N. A case of congenital ectopic nail. Hiliii 1981: 26: U)13 (ill Japanese). 11. felfer NR, Bartli j H , Dawber RPR. (Congenital and hetc-ditary nail dystrophies — an embiyological approach to classification. Glin Fxp Detniatof 1988: 13: 160. 12. Kikiicbi 1, I Iorika\\a S, .Amano V. Gongenital onychodysplasia ofthe index fmgers. .Arch Dc-rmatol 1971: 110: 743. 1!!. SiKcrman RA. Pcdiatric disease. In: Sc4ier RK, Daniel ('R, eds. Nails: 4'herapy, Diagnosis, Surgery. Philadeljihia: WB Saunders, 1990: 82. M. Kligman AM. Why do nails grow out instead of up:' .Nreb Detmatol 1961: 84: 313. LS. Kligman .AM. Resi>onse. J Am Aead Dermatol 1981: 1: 83. Hi. Baran R. Nail growth direction revisited. Why do nails grow out instead of up? J .Am .Aead Dermatol 1981: 4: 78.
447
