Dermatology: Practical and Conceptual Review | Dermatol Pract Concept. 2023;13(1):e2023072 1 Dermoscopy of Onychomycosis: A Systematic Review Noureddine Litaiem1,2, Emna Mnif1, Faten Zeglaoui1,2 1 Department of Dermatology, Charles Nicolle Hospital, Tunis, Tunisia 2 University of Tunis El Manar, Faculté de Médecine de Tunis, Tunisia Key words: onychomycosis, Tinea unguium, onychoscopy, dermatoscopy, Dermoscopy Citation: Litaiem N, Mnif E, Zeglaoui F. Dermoscopy of onychomycosis: A systematic review. Dermatol Pract Concept. 2023;13(1):e2023072. DOI: https://doi.org/10.5826/dpc.1301a72 Accepted: August 22, 2022; Published: January 2023 Copyright: ©2023 Litaiem 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: Noureddine Litaiem, Department of Dermatology, Charles Nicolle Hospital, Tunis, Tunisia. E-mail: Noureddine.litaiem@gmail.com Introduction: Onychomycosis represents a global burden accounting for about 50% of nail consulta- tions. Several studies have tried to assess the dermoscopic features of onychomycosis. With the multi- plication of papers, several “new” dermoscopic signs keep being added leading to some inconsistency in onychoscopic terminology. Objective: This study aimed to summarize the existing literature on the dermoscopic features of onychomycosis and propose a unified onychoscopic terminology. Methods: The literature search was performed using PubMed and Scopus databases up to October 30, 2021 to identify eligible contributions. In total, 33 records (2111 patients) were included. Results: The main dermoscopic signs of onychomycosis are “ruin appearance”, “longitudinal striae” and “spikes” on the proximal margin of onycholytic areas, with a specificity of 99.38%, 83.78%, and 85.64% respectively. The “aurora borealis” sign had the highest sensitivity and specificity. Conclusions: The current review provides a framework for issues related to the onychoscopic termi- nology of onychomycosis and is intended to serve as an aid for students, teachers, and researchers. We proposed a unifying terminology to describe dermoscopic signs of onychomycosis. Dermoscopic signs of onychomycosis show good specificity and are useful in distinguishing nail psoriasis, trauma, and onychomycosis. It helps differentiate fungal melanonychia from nail melanoma, nevi, and melanocytic activation. ABSTRACT 2 Review | Dermatol Pract Concept. 2023;13(1):e2023072 Introduction Onychomycosis represents all fungal infections of the nail. It is frequent, accounting for about 50% of nail consulta- tions  [1]. Onychomycosis could be due to dermatophytes (tinea unguium) as well as non-dermatophytes. Management of onychomycosis is challenging due to diagnostic difficul- ties, slow nail regrowth, long treatment periods, resistance to systemic medications, possible related side effects, and frequent recurrences. Direct microscopy and fungal culture are the gold standards for the diagnosis of onychomyco- sis. However, fungal culture has low sensitivity (35–60%) and may require several weeks [2]. Dermoscopy of the nail unit (onychoscopy) is a quick, inexpensive, and reliable tool used for the diagnosis of cutaneous tumors, inflammatory disorders, and skin infections. Several studies addressed the dermoscopic signs of onychomycosis frequently using meta- phorical terminology [3]. With “new signs” being introduced (like the “sulphur nuggets” aspect) and the absence of a widely accepted consensus on the onychoscopic terminology, some degree of discrepancy among the definitions of the der- moscopic signs of onychomycosis exists (Table 1). Dermoscopy can help differentiate onychomycosis from similar conditions including nail psoriasis and traumatic nail dystrophy [3] and can be used to characterize fungal melanonychia [4–7]. However, the sensitivity and specific- ity of the dermoscopic signs of onychomycosis are yet to be determined. The aim of this study was to summarize the existing lit- erature on the dermoscopic features of onychomycosis and its diagnostic value and propose a unified onychoscopic terminology. Methods This literature search was performed using PubMed and Scopus databases (from the databases’ inception up to October  30, 2021) to identify eligible contributions. The following search strategy was used: (“onychomycosis” OR “Tinea unguium” OR “nail fungal infection”) AND (“ onychoscopy” OR “dermatoscopy” OR “Dermoscopy” OR “videodermatoscopy” OR “videodermoscopy”). Two dermatologists (N.L. and E.M.) independently screened titles and abstracts for eligibility. Only papers in the English language were considered for inclusion. Editorials, commentary, and review articles were excluded. All contri- butions reporting one or multiple cases of onychomycosis and describing its dermoscopic features were included. Ref- erence lists of included articles were further screened for ad- ditional eligible publications. Any discrepancy between the 2 authors (N.L. and E.M.) was resolved by consensus. Each eligible article was retrieved in full, and the epidemiological, mycological, dermoscopic, and histopathological data were extracted. Both descriptive and analytical statistics were performed. The dermoscopic features of onychomycosis were first an- alyzed based on the initial description by the authors of included articles (Table 2). Then the following terms that share the same definition: “jagged edge with spikes”, “spiked pattern” and “intermittent spiked pattern” were grouped as “spikes” for analytical statistics. Chi-squared test, when applicable, or Fischer exact test, were used to examine differences in categorical variables. The sensitivity and specificity of the most frequently re- ported dermoscopic features of onychomycosis were calcu- lated. A P-value lower than 0.05 was considered significant. Results The literature search yielded 180 records. Of the 110 papers examined after duplicate removal, 36 were review articles, and 32 were not relevant. Overall, 5 contributions were not in the English language, and 7 did not include information regarding the frequency of dermoscopic signs of onychomy- cosis. Consequently, 33 records were included in this review [2,3,12–21,4,22–31,5,32–34,6–11]. The process of selecting relevant articles is illustrated in Figure 1. In total, 2048 patients with onychomycosis were in- cluded. The clinical classification of onychomycosis is di- vided into 6 patterns based on the point of fungal entry into the nail unit. The clinical classification of onychomycosis was specified in 1885 cases: • Distal/lateral subungual onychomycosis (DLSO): 1514, 71.7% • Superficial onychomycosis (SO): 31, 1.6% • Proximal subungual onychomycosis (PSO): 21, 1.1% • Total dystrophic onychomycosis (TDO): 266, 14.1% • Mixed pattern (MO): 51, 2.7% • Endonyx onychomycosis: 2 cases Methods to diagnose onychomycosis were described in 27 of the included papers. The diagnosis was based on KOH examination [4,7,11,16,17,23,27–32,35], fungal culture [2,3,5,8,13,16,19,20,24,25,33,34], and/or histologic exam- ination of nail plates [5,8,10,19,20,24]. The dermoscopic features of onychomycosis are summa- rized in Table 2. The most common onychoscopic signs were: Ruin Appearance Ruin appearance refers to the distal part of the thickened nail plate showing ventral indentations caused by dermal Review | Dermatol Pract Concept. 2023;13(1):e2023072 3 Table 1. Definitions. Dermoscopic features Definitions Ruin appearance Ventral indentations of the nail plate caused by dermal debris. Some authors consider that ruin appearance and subungual hyperkeratosis are the same sign19,32, while others defined ruin appearance as a distal irregular termination at the edge of the nail plate30. Subungual hyperkeratosis Hyperkeratosis of the subungual area under the distal margin of the nail plate4 Sulphur nuggets Described for the first time by Leeyaphan et al. as yellow clumping sulfur nugget-like debris under the nail plate.8 Longitudinal striae Longitudinal pigmentation of different colors in streaks within the nail plate onycholysis Separation of the nail plate from the nail bed Jagged edge with spikes/ spiked pattern A nonlinear border at the proximal edge of an onycholysis area, with a sharp white longitudinal indentation pointing to the proximal nail fold Straight onycholytic edge A linear edge of the proximal margin of an onycholytic area without indentations Distal irregular termination Refers to the distal pulverization of the nail plate17,23,29 Splinter hemorrhage Longitudinal brown, black, or purple linear hemorrhages30 Chromonychia multicolored, black, brown, white or yellow pigmentation of the nail plate. Aurea borealis Area of various colors associating various degrees of green, bluish- gray, black, white, and yellow in association with onycholysis, striae and streaks.11 Some authors consider “jagged edge with spikes” sign to be equivalent to “aurora borealis” pattern.29 Leukonychia True leukonychia A white discoloration throughout the entire thickness of the nail plate, responsible for the opaque appearance Pseudo leukonychia Seen in white superficial onychomycosis (SO), where only the superficial surface of the nail plate is invaded.29 Homogeneous leukonychia Homogenous white opacity of the nail plate, greater than 1 mm in size.19,20 Punctate leukonychia White globules with dimensions of less than 1 mm on the nail plate19 Longitudinal leukonychia White parallel lines in the nail plate Transverse leukonychia Horizontal white striae in the nail plate Grid pattern Seen in superficial onychomycosis (SO). The grid pattern is the result of the intersection of longitudinal and transverse leukonychia.10 Melanonychia Longitudinal melanonychia A longitudinal band extending from the proximal nail fold to the distal free edge of the nail plate Non-longitudinal homogenous pattern Structureless pigmentation of the nail plate Reverse triangular pattern Nail pigmentation that is wider at the distal end compared to the proximal part of the nail plate Triangular sign Nail pigmentation is wider at the proximal area compared to the distal end of the nail plate Micro Hutchinson Cuticular pigmentation that is normally invisible to the naked eye Hutchinson sign Nailfold or hyponychium pigmentation Pseudo-Hutchinson sign Nail matrix pigmentation detected through a relatively translucent cuticle at the proximal nail fold.4 4 Review | Dermatol Pract Concept. 2023;13(1):e2023072 The frequency of linear edge in OM varied between 2% and 22% (a mean of 8%) and it is thought to be secondary to trauma preceding OM [36]. Spikes “Spiked pattern”, “intermittent spiked pattern” and “Jagged edge with spikes” share the same definition. It is character- ized as indentations at the proximal edge of the onycholy- tic area (Figure 2c) [23]. These structures correspond to the distal-to-proximal invasion of the nail bed’s longitudinal ridges by dermatophytes [3,11,23]. The frequency of jagged edges with spikes varied between 39% and 100% (a mean of 58%) [3,5–9,12–15,17–21,24,29–34,36]. These structures were significantly associated with DLSO, very frequent in TDO, and never described in SO, PSO and endonyx onycho- mycosis (Table 3). Spikes can also be seen in onychorrhexis, but are located in the proximal part of the nail [11,26]. Spikes help differen- tiate onycholysis related to trauma and onychomycosis. The former is virtually never associated with spikes. Chromonychia Chromonychia is defined as a discoloration of the nail plate. It may be secondary to colony formation, flakes, or subungual debris [15,23,26]. The colors ranged from white (leukonychia), green, yellow, brown, gray, and black. The prevalence of chromonychia varies between 22 and 100% debris (Figure 2a) [19]. It corresponds to the fungal presence in the nail plate [19,26]. For some authors, “ruin appear- ance”, “distal irregular termination” [30], and “subungual hyperkeratosis” [19,32] can be used interchangeably. The frequency of ruin appearance varied between 13% and 100% (a mean of 68%) [2,7,8,12,19–23,26,29,30,34]. Ruin appearance was significantly associated with DLSO and never described in SO and endonyx onychomycosis (Table 3). Longitudinal Striae: Longitudinal striae appear as streaks within the nail plate and are the result of the fungal invasion of the nail plate (Figure 2b) [26]. They were reported in 64.9% of cases. Longitudinal striae are very frequent in DLSO, TDO, and rarely reported in SO (p=0.001), and PSO (p=0.03). Onycholysis Onycholysis is the separation of the nail plate from the nail bed. According to Zaias et al, the main etiology of onycholysis is trauma and onychomycosis is never the initiating factor [36]. Dermoscopy helps differentiate onycholysis of traumatic origin from onychomycosis. A linear edge at the proximal aspect of onycholysis is associated with trauma, while spikes are associated with onychomycosis (Figure 2c) [23].  In on- ychomycosis, the frequency of onycholysis varies between 5 and 100% (a mean of 65%). Table 2. Summary of the dermoscopic features of onychomycosis. Dermoscopic features N, percentage Ruin appearance 752,68% Longitudinal striae 1351, 64.9% onycholysis 252, 65.3% Jagged edge with spikes/spiked pattern 740, 58% / 516, 57.3% Straight onycholytic edge 55, 8.2% Distal irregular termination 340, 36% Splinter hemorrhage 26, 5.3% Chromonychia 531, 70.4% Homogeneous leukonychia 120, 33.4% Punctate leukonychia 113, 75,8% Transverse leukonychia 18, 10.4% Leukonychia (unspecified pattern) 182, 31.8% Black discoloration 212, 23.9% Brown discoloration 268, 36.9% Yellow discoloration 365, 57% Orange discooration 69, 19.5% Gray discoloration 29, 11.6% Green discoloration 92, 40.8% N: number of reported cases Review | Dermatol Pract Concept. 2023;13(1):e2023072 5 Leukonychia: Leukonychia is a white coloration of the nail. It is explained by the fungal growth in the nail plate, similar to the growth in the culture medium [19]. It can be punctate, transverse (Figure 2d), or homogenous (Table 1). The frequency of leukonychia var- ies between 2% and 75 % (a mean of 37%) [2,6,19,20,29]. Leukonychia was significantly associated with SO (p<0.001). (a mean of 70.4%). The most frequent color was yellow (a mean of 57%) [4,8,9,13,14,16,19,20,28–32,34,36,37]. The association of chromonychia of multiple colors with longitudinal striae, spikes, and onycholysis creates a pattern called “aurora borealis” or “aurora sign” (Figure 3) because they resemble waves of northern lights or aurora borealis [30]. RECORDS IDENTIFIED FROM DATABASES (n=180) IDENTIFICATION OF STUDIES VIA DATABASES (PUBMED AND SCOPUS) ID EN TI FI CA TI O N SC RE EN IN G EL IG IB IL IT Y IN CL U D ED RECORDS AFTER DUPLICATES REMOVES (n=113) REPORTS SCREENED (n=113) RECORDS EXCLUDED (n=36): EDITORIALS, REVIEWS, COMMENTARY (n=32): NOT RELEVANT FULL-TEXT ARTICLES EXCLUDED WITH REASONS: NOT IN ENGLISH LANGUAGE (n=5) NO INFORMATION REGARDING THE PRECISE FREQUENCY OF DERMOSCOPIC FEATURES OF ONYCHOMYCOSIS (n=7) FULL-TEXT ARTICLES ASSESSED FOR ELIGIBILITY (n=45) STUDIES INCLUDED IN QUALITIVE SYNTHESIS (n=33) STUDIES INCLUDED IN QUANTITATIVE SYNTHESIS (n=33) Figure 1. Flow diagram. 6 Review | Dermatol Pract Concept. 2023;13(1):e2023072 Figure 2. Dermoscopic features of onychomycosis. (A) “ruin appearance”. (B) longitudinal striae. (C) spikes on the proximal edge of an onycholytic area. (D) transverse leukonychia. Fungal Melanonychia Fungal melanonychia is a dark pigmentation of the nail plate. It is explained by the synthesis of melanin by some fungi. The best-characterized fungal melanin is 1,8- dihydroxynaphthalene (DHN) melanin. Its biosynthetic pathway is called the pen- taketide pathway. The name “Pentaketide” derives from the fact that the naphthalene ring structure, that underlies the DHN-melanin pathway is formed by the binding and cycliza- tion of five subunits of a ketone compound derived from five acetate molecules. Fungal melanin protects the fungus from the aggressions of the environment [37]. Dermoscopy helps distinguish fungal melanonychia from nail melanoma, nail matrix nevus, and melanocytic activa- tion [4,5,7,9]. Yellow and red discoloration are significantly associated with fungal melanonychia, while the triangular sign and Hutchinson sign are features of nail melanoma and never described in association with onychomycosis (Table  4). Conversely, distal linear and reverse triangular patterns are signs of fungal melanonychia (Table 4). Indeed, in fungal melanonychia, the pigmentation is wider at the distal por- tion of the nail due to the distal-to-proximal progression of fungi which is responsible for the reverse triangular pattern (Figure 4). However, in nail melanomas, the pigmentation is wider in the proximal portion, resulting in a triangular melanonychia [30]. Splinter Hemorrhage Splinter hemorrhages are linear hemorrhages caused by bleeding capillaries[16]. It is a common yet nonspecific sign of onychomycosis. It is reported in association with trauma and psoriasis[25]. The prevalence of splinter hemorrhage in onychomycosis varies between 2% and 25% (a mean of 5%) [11,17,19,21,34,36]. Sensitivity and Specificity of the Dermoscopic Signs of Onychomycosis: Several studies compared the dermoscopic features of onychomycosis, psoriasis, and traumatic nail dystrophy [3,8,11,12,25]. The sensitivity and specificity of the dermo- scopic signs of onychomycosis are summarized in Table 5. Overall the sensitivity of “ruin appearance”, “longitudi- nal striae”, and “spikes” are low with good specificity ( Table  5). The “Aurora borealis” sign showed the highest sensitivity and specificity. Some dermoscopic signs were only Review | Dermatol Pract Concept. 2023;13(1):e2023072 7 Ta b le 3 . D er m os co pi c as pe ct s an d th ei r as so ci at io n w it h cl in ic al s ub ty pe s of o ny ch om yc os is . D LS O SO PS O M O TD O O n yc h o m yc o si s en d o n yx Fr eq u en cy P- V al u e Fr eq u en cy P- V al u e Fr eq u en cy P- V al u e Fr eq u en cy P- V al u e Fr eq u en cy P- V al u e Fr eq u en cy P- V al u e R ui n ap pe ar an ce 14 2/ 20 6 0. 01 6 0/ 5 0. 00 1 1/ 4 N S - - 53 /5 5 N S 0 - L on gi tu di na l st ri ae 32 6/ 49 6 N S 2/ 13 0. 00 1 3/ 11 0. 03 20 /4 7 - 11 7/ 21 0 N S 2/ 2 N S Sp ik es ( Ja gg ed ed ge w it h sp ik es / Sp ik ed p at te rn ) 40 3/ 65 7 0. 00 2 4/ 21 N S 2/ 18 0. 02 9 34 /9 4 N S 95 /2 59 N S 0/ 2 N S D is ta l i rr eg ul ar te rm in at io n 15 4/ 46 2 N S 1/ 12 0. 01 7 5/ 10 N S 14 /4 7 N S 12 6/ 18 6 N S 0/ 2 N S L eu ko ny ch ia 56 /2 56 0. 01 7 7/ 7 0. 00 01 1/ 7 N S 34 /4 7 N S 0/ 58 N S 2/ 2 N S D L SO : D is ta l/l at er al s ub un gu al o ny ch om yc os is ; M O : M ix ed p at te rn ; N S: n on -s ig ni fic an t; P SO : P ro xi m al s ub un gu al o ny ch om yc os is ( PS O ); S O : S up er fic ia l o ny ch om yc os is ; T D O : To ta l d ys tr op hi c on yc ho m yc os is ; 8 Review | Dermatol Pract Concept. 2023;13(1):e2023072 Figure 3. “Aurora borealis” sign. Chromonychia of multiple colors, associated with onycholysis, spikes and longitudinal striae. Table 4. Characteristics of melanonychia in patients with onychomycosis, nail matrix naevus, melanoma, and melanocytic activation. Fungal melanonychia Nail matrix nevus Malignant melanoma Melanocytic activation P-value color black 35/128 12/27 16/25 0/24 0.16 dark brown 46/128 12/27 17/25 0/24 0.76 light brown 32/86 16/27 7/25 5/24 1 yellow 27/86 1/27 3/25 2/24 0.0001 grey 24/148 0/27 7/25 20/24 0.002 red 12/58 0/27 1/25 0/24 0.0001 multicolored 49/100 13/27 22/25 4/24 0.87 clumped/granular black 23/62 - - - - pigmentation pattern longitudinal pattern 57/148 26/27 17/25 24/24 1 distal diffuse pattern 20/88 - 6/14 - 0.18 proximal diffuse pattern 7/88 - 2/14 - 0.60 distal linear pattern 7/88 - 0/14 - 0.58 total diffuse pattern 21/88 - 5/14 - 0.33 reverse triangular pattern 19/58 0/27 1/25 0/24 1 triangular sign 0/86 3/27 9/25 0/24 - Hutchinson sign 0/106 1/27 16/25 0/24 - pseudo Hutchinson sign 3/106 10/27 15/25 2/24 1 superficial transverse striation 18/62 - - - - reported in association with psoriasis including red dots in the hyponychium and lateral folds, proximal erythematous rim of onycholytic areas, and salmon patches, while plain non-erythematous edges of onycholytic areas are only de- scribed in association with trauma. Discussion This is the first systematic review addressing the dermoscopic features of onychomycosis. The main dermoscopic signs of on- ychomycosis are “ruin appearance”, “longitudinal striae” and “spikes” on the proximal margin of onycholytic areas, with a specificity of 99.38%, 83.78%, and 85.64% respectively. The “aurora borealis” sign had the highest sensitivity and specificity. Dermoscopy improves the diagnostic accuracy for cuta- neous lesions in comparison with the naked eye examina- tion [38]. Since the first description [3], several studies tried to assess the dermoscopic features of onychomycosis. With the multiplication of papers, and the inexistence of a widely adopted international consensus on onychoscopy similar to those related to cutaneous lesions [38], several “new” dermo- scopic signs keep being added [8]. This results in some incon- sistency between authors on the terminology to be used to describe dermoscopic features of onychomycosis (Table 1). Review | Dermatol Pract Concept. 2023;13(1):e2023072 9 while metaphorical terminology is memorable but incompre- hensible outside its context [38]. We suggest the following terminology for the most prevalent onychoscopic signs of onychomycosis: • “ruin appearance” (metaphoric) = subungual hyperkera- tosis with distal irregular termination (descriptive) • “longitudinal striae” (descriptive) • “spikes” (metaphoric) to replace “spiky pattern”, “Jagged edge with spikes” and “spiked pattern” Following the third consensus conference of the Interna- tional Society of Dermoscopy, standardization of terminol- ogy in dermoscopy of cutaneous lesions was adopted [38]. Both descriptive and metaphorical terminology was consid- ered acceptable for clinical use and research [38]. Similarly, we believe that both descriptive and analytical terminology can be used to describe dermoscopic signs of onychomyco- sis. Descriptive (analytical) terminology has the advantage of being comprehensible and suitable for learning, and the dis- advantage of possible long descriptive complex structures, Figure 4. Fungal melanonychia. (A) reverse triangular pattern. (B) distal longitudinal pattern. Table 5. Sensitivity and specificity of the dermoscopic signs of onychomycosis. Onychomycosis Trauma Psoriasis Sensitivity (%) Specificity (%) Spikes 141/211 24/147 0/41 66.82 85.64 Longitudinal striae 76/191 24/142 0/6 39.79 83.78 Subungual hemorrhage 17/137 18/120 - 12.41 85 Splinter hemorrhage 6/147 11/96 23/41 4.08 75.18 Onycholysis 31/154 42/129 6/6 20.13 61.9 Ruin appearance 28/157 1/125 0/35 17.83 99.38 Red dots in hyponychium 0/20 0/5 26/35 * * Red dots in lateral folds 0/20 0/5 24/35 * * Proximal erythematous rim associated with onycholysis 0/37 0/14 26/41 * * Plain edges without erythema 0/74 26/27 0/41 ** ** Deep pits and dots 24/74 9/27 14/41 32.43 66.18 Salmon patch 0/20 0/5 9/35 * * Subungual hyperkeratosis 5/20 0/5 17/35 25 57.5 Aurora borealis 17/20 0/5 0/35 85 100 *the sign was only described in patients with psoriasis** the sign was only described in association with trauma 10 Review | Dermatol Pract Concept. 2023;13(1):e2023072 2. Litaiem N, Nakouri I, Bouhlel S, et al. Dermoscopic fea- tures of toenail onychomycosis. J Am Podiatr Med Assoc. 2020;110(3):1-4. doi:10.7547/18-102 3. Piraccini BM, Balestri R, Starace M, et al. Nail digital der- moscopy (onychoscopy) in the diagnosis of onychomycosis. 2013;27(4):509-513. doi:10.1111/J.1468-3083.2011.04323.X 4. Ohn J, Choe YS, Park J, et al. Dermoscopic patterns of fun- gal melanonychia: A comparative study with other causes of melanonychia. J Am Acad Dermatol. 2017;76(3):488-493.e2. doi:10.1016/J.JAAD.2016.08.013 5. Kilinc Karaarslan I, Acar A, Aytimur D, et al. Dermo- scopic features in fungal melanonychia. Clin Exp Dermatol. 2015;40(3):271-278. doi:10.1111/CED.12552 6. Starace M, Ambrogio F, Bruni F, et al. Dermatophytic mela- nonychia: A case series of an increasing disease. Mycoses. 2021;64(5):511-519. doi:10.1111/MYC.13237 7. Kim HJ, Kim TW, Park SM, et al. Clinical and Dermoscopic Fea- tures of Fungal Melanonychia: Differentiating from Subungual Melanoma. Ann Dermatol. 2020;32(6):460-465. doi:10.5021 /AD.2020.32.6.460 8. Leeyaphan C, Suphatsathienkul P, Limphoka P, et al. Sulphur Nuggets. Med Mycol J. 2021;62(3):21-00006. doi:10.3314 /MMJ.21-00006 9. Elmas ÖF, Metin MS. Dermoscopic findings of fungal melanony- chia. Postep Dermatologii i Alergol. 2020;37(2):180-183. 10. Grover C, Jakhar D, Sharma S. The grid pattern of white su- perficial onychomycosis. Indian J Dermatol Venereol Leprol. 2020;86(5):568-570. doi:10.4103/IJDVL.IJDVL_699_19 11. Ankad BS, Gupta A, Alekhya R, et al. Dermoscopy of Onycholy- sis Due to Nail Psoriasis, Onychomycosis and Trauma: A Cross Sectional Study in Skin of Color. Indian Dermatol Online J. 2020;11(5):777-783. doi:10.4103/IDOJ.IDOJ_475_19 12. Ramos Pinheiro R, Dias Domingues T, Sousa V, et al. A com- parative study of onychomycosis and traumatic toenail • chromonychia (descriptive): nail discoloration • leukonychia (descriptive): white discoloration of the nail plate We also suggest that the pigmentation patterns described in Table 4 should be used as-is since these patterns are widely used in onychoscopic terminology and there are no related discrepancies between published articles [3–5,7]. Dermoscopy is very useful in diagnosing pigmented nails. Chromonychia is very frequent in onychomycosis with yel- low and red discoloration being significantly associated with fungal melanonychia. Other signs help distinguish fungal melanonychia from nail melanoma including distal linear and reverse triangular patterns. Conversely, the triangular pattern and Hutchinson sign are features of nail melanoma [4–7,9]. In conclusion, dermoscopy is useful in diagnosing ony- chomycosis. The current review provides a framework for issues related to onychoscopic terminology of onychomyco- sis and is intended to serve as an aid for students, teachers, and researchers. Dermoscopic signs of onychomycosis show good specificity and are useful in distinguishing nail psoria- sis, trauma, and onychomycosis. It helps differentiate fungal melanonychia from nail melanoma, nevi, and melanocytic activation and allows precise monitoring of nail regrowth after systemic antifungal treatment initiation (Figure 5). References 1. Piraccini BM, Alessandrini A. Onychomycosis: A Review. J Fungi (Basel). 2015;1(1):30-43. doi:10.3390/jof1010030 Figure 5. Clinical and Dermoscopic images of the same patient. Response to treatment may be better visualized using Dermoscopy allowing precise measurement of nail regrowth. Review | Dermatol Pract Concept. 2023;13(1):e2023072 11 Soc. 2015;12(3):145-149. doi:10.1097/01.EWX.0000469303 .65552.A1 26. De Crignis G, Valgas N, Rezende P, et al. Dermatoscopy of ony- chomycosis. Int J Dermatol. 2014;53(2). doi:10.1111/IJD.12104 27. Di Chiacchio N, Noriega LF, Gioia Di Chiacchio N, et al. Su- perficial black onychomycosis due to Neoscytalidium dimidia- tum. J Eur Acad Dermatology Venereol. 2017;31(10):e453-e455. doi:10.1111/JDV.14273 28. Bet DL, dos Reis AL, Di Chiacchio N, et al. Dermoscopy and onychomycosis: Guided nail abrasion for mycological sam- ples. An Bras Dermatol. 2015;90(6):904-906. doi:10.1590/ ABD1806-4841.20154615 29. Devi Sangeetha A, Gopalakrishnan K, Ramachandran R, et al. A descriptive study of onychoscopic features in various subtypes of onychomycosis. Med J Armed Forces India. Published online 2021. doi:10.1016/J.MJAFI.2021.03.019 30. Hazarika N, Chauhan P, Divyalakshmi C, et al. Onychoscopy: A quick and effective tool for diagnosing onychomycosis in a resource-poor setting. Acta Dermatovenerologica Alpina, Pannon- ica Adriat. 2021;30(1):11-14. doi:10.15570/ACTAAPA.2021.3 31. Sato T, Kitahara H, Honda H, et al. Onychomycosis of the mid- dle finger of a Japanese judo athlete due to trichophyton ton- surans. Med Mycol J. 2019;60(1):1-4. 32. Yorulmaz A, Yalcin B. Dermoscopy as a first step in the di- agnosis of onychomycosis. Postep Dermatologii i Alergol. 2018;35(3):251-258. 33. Nada EE din A, El Taieb MA, El-Feky MA, et al. Diagnosis of onychomycosis clinically by nail dermoscopy versus microbio- logical diagnosis. Arch Dermatol Res. 2020;312(3):207-212. doi:10.1007/S00403-019-02008-6 34. González Cortés LF, Prada L,et al. Onychoscopy in a Colombian population with a diagnosis of toenail onychomycosis: an eval- uation study for this diagnostic test. Clin Exp Dermatol. Pub- lished online 2021. doi:10.1111/CED.14706 35. Campos S, Lencastre A. Dermatoscopic Correlates of Nail Appa- ratus Disease: A Look at the Nail From Another Scope, the Der- matoscope. Imaging in Dermatology. Published online August 19, 2016:43-58. doi:10.1016/B978-0-12-802838-4.00005-4 36. Zaias N, Escovar SX, Zaiac MN. Finger and toenail onycholy- sis. J Eur Acad Dermatology Venereol. 2015;29(5):848-853. doi:10.1111/JDV.12862 37. Jin H, Kim JM, Kim GW, et al. Diagnostic criteria for and clinical review of melanonychia in Korean patients. J Am Acad Derma- tol. 2016;74(6):1121-1127. doi:10.1016/J.JAAD.2015.12.039 38. Kittler H, Marghoob AA, Argenziano G, et al. Standardization of terminology in dermoscopy/dermatoscopy: Results of the third consensus conference of the International Society of Der- moscopy. J Am Acad Dermatol. 2016;74(6):1093. doi:10.1016/J .JAAD.2015.12.038 onychodystrophy dermoscopic patterns. J Eur Acad Dermatol- ogy Venereol. 2019;33(4):786-792. doi:10.1111/JDV.15358 13. Abdallah NA, Said M, Mahmoud MT, et al. Onychomycosis: Correlation between the dermoscopic patterns and fungal cul- ture. J Cosmet Dermatol. 2020;19(5):1196-1204. doi:10.1111 /JOCD.13144 14. Bhat YJ, Keen A, Hassan I, et al. Can Dermoscopy Serve as a Diagnostic Tool in Dermatophytosis? A Pilot Study. 2019;10(5). doi:10.4103/IDOJ.IDOJ_423_18 15. Maatouk I, Haber R, Benmehidi N. Onychoscopic evaluation of distal and lateral subungual onychomycosis: A cross-sectional study in Lebanon. Curr Med Mycol. 2019;5(2):41-44. doi:10.18502/CMM.5.2.1161 16. Bhat YJ, Mir MA, Keen A, Hassan I. Onychoscopy: an observa- tional study in 237 patients from the Kashmir Valley of North India. Dermatol Pract Concept. Published online October 31, 2018:283-291. doi:10.5826/DPC.0804A06 17. Chetana K, Menon R, David BG. Onychoscopic evaluation of on- ychomycosis in a tertiary care teaching hospital: a cross-sectional study from South India. Int J Dermatol. 2018;57(7):837-842. doi:10.1111/IJD.14008 18. Nargis T, Pinto M, Shenoy MM, et al. Dermoscopic Features of Distal Lateral Subungual Onychomycosis. Indian Dermatol On- line J. 2018;9(1):16-19. doi:10.4103/IDOJ.IDOJ_40_17 19. Kaynak E, Göktay F, Güneş P, et al. The role of dermoscopy in the diagnosis of distal lateral subungual onychomycosis. Arch Der- matol Res. 2018;310(1):57-69. doi:10.1007/S00403-017-1796-2 20. Kayarkatte M, Singal A, Pandhi D, et al. Nail dermoscopy (on- ychoscopy) findings in the diagnosis of primary onychomyco- sis: A cross-sectional study. Indian J Dermatol Venereol Leprol. 2020;86(4):341-349. doi:10.4103/IJDVL.IJDVL_100_19 21. Bodman MA. Point-of-care diagnosis of onychomycosis by dermoscopy. J Am Podiatr Med Assoc. 2017;107(5):413-418. doi:10.7547/16-183 22. Kallis P, Tosti A. Dermoscopy as a first step in the diagnosis of onychomycosis. 1(4). doi:10.1159/000445908 23. Jesús-Silva MA, Fernández-Martínez R, Roldán-Marín R, et al. Dermoscopic patterns in patients with a clinical diagno- sis of onychomycosis-results of a prospective study including data of potassium hydroxide (KOH) and culture examina- tion. Dermatol Pract Concept. 2015;5(2):39-44. doi:10.5826 /DPC.0502A05 24. El-Hoshy KH, Abdel Hay RM, El-Sherif RH, et al. Nail der- moscopy is a helpful tool in the diagnosis of onychomycosis: A case control study. Eur J Dermatology. 2015;25(5):494-495. doi:10.1684/EJD.2015.2637 25. Elfar NN, Abdel-Latif AM, Labeh EA. Role of onychoscopy in differentiation between distal subungual onychomycosis, psoria- sis, and traumatic onycholysis. J Egypt Women’s Dermatologic