10.5826/dpc.1301a72
Introduction:
Onychomycosis represents a global burden accounting for about 50% of nail consultations. Several studies have tried to assess the dermoscopic features of onychomycosis. With the multiplication 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 terminology 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.
text/xml
2160-9381
2596
en
Faten Zeglaoui
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
dermoscopy
Dermoscopy of Onychomycosis: A Systematic Review
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Review
2023-01-31
2022-05-15
2023-01-31
2023-02-27
e2023072
Dermatol Pract Concept
Introduction:
Onychomycosis represents a global burden accounting for about 50% of nail consultations. Several studies have tried to assess the dermoscopic features of onychomycosis. With the multiplication 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 terminology 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.
Faten Zeglaoui
2023/01/31
10.5826/dpc.1301a72
e2023072
Department of Dermatology, Charles Nicolle Hospital; University of Tunis El Manar, Faculté de Médecine de Tunis, Tunisia
2160-9381
dermoscopy
en
e2023072
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 Dermoscopy. J Am Acad Dermatol. 2016;74(6):1093. doi:10.1016/J.JAAD.2015.12.038
Dermoscopy of Onychomycosis: A Systematic Review
https://dpcj.org/index.php/dpc/article/download/2596/1961
                           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




  ABSTRACT             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 O      ­ ctober 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.




Review | Dermatol Pract Concept. 2023;13(1):e2023072                                                                                1
Introduction                                                        eligible article was retrieved in full, and the epidemiological,
                                                                    mycological, dermoscopic, and histopathological data were
Onychomycosis represents all fungal infections of the nail.         extracted.
It is frequent, accounting for about 50% of nail consulta-             Both descriptive and analytical statistics were performed.
tions [1]. Onychomycosis could be due to dermatophytes              The dermoscopic features of onychomycosis were first an-
(tinea unguium) as well as non-dermatophytes. Management            alyzed based on the initial description by the authors of
of onychomycosis is challenging due to diagnostic difficul-         included articles (Table 2). Then the following terms that
ties, slow nail regrowth, long treatment periods, resistance        share the same definition: “jagged edge with spikes”, “spiked
to systemic medications, possible related side effects, and         pattern” and “intermittent spiked pattern” were grouped as
frequent recurrences. Direct microscopy and fungal culture          “spikes” for analytical statistics.
are the gold standards for the diagnosis of onychomyco-                Chi-squared test, when applicable, or Fischer exact test,
sis. However, fungal culture has low sensitivity (35–60%)           were used to examine differences in categorical variables.
and may require several weeks [2]. Dermoscopy of the nail           The sensitivity and specificity of the most frequently re-
unit (onychoscopy) is a quick, inexpensive, and reliable tool       ported dermoscopic features of onychomycosis were calcu-
used for the diagnosis of cutaneous tumors, inflammatory            lated. A P-value lower than 0.05 was considered significant.
disorders, and skin infections. Several studies addressed the
dermoscopic signs of onychomycosis frequently using meta-
phorical terminology [3]. With “new signs” being introduced
                                                                    Results
(like the “sulphur nuggets” aspect) and the absence of a            The literature search yielded 180 records. Of the 110 papers
widely accepted consensus on the onychoscopic terminology,          examined after duplicate removal, 36 were review articles,
some degree of discrepancy among the definitions of the der-        and 32 were not relevant. Overall, 5 contributions were not
moscopic signs of onychomycosis exists (Table 1).                   in the English language, and 7 did not include information
    Dermoscopy can help differentiate onychomycosis from            regarding the frequency of dermoscopic signs of onychomy-
similar conditions including nail psoriasis and traumatic           cosis. Consequently, 33 records were included in this review
nail dystrophy [3] and can be used to characterize fungal           [2,3,12–21,4,22–31,5,32–34,6–11]. The process of selecting
melanonychia [4–7]. However, the sensitivity and specific-          relevant articles is illustrated in Figure 1.
ity of the dermoscopic signs of onychomycosis are yet to be            In total, 2048 patients with onychomycosis were in-
determined.                                                         cluded. The clinical classification of onychomycosis is di-
    The aim of this study was to summarize the existing lit-        vided into 6 patterns based on the point of fungal entry into
erature on the dermoscopic features of onychomycosis and            the nail unit. The clinical classification of onychomycosis
its diagnostic value and propose a unified onychoscopic             was specified in 1885 cases:
terminology.

                                                                    • Distal/lateral     subungual        onychomycosis    (DLSO):
                                                                      1514, 71.7%
Methods                                                             • Superficial onychomycosis (SO): 31, 1.6%
This literature search was performed using PubMed and               • Proximal subungual onychomycosis (PSO): 21, 1.1%
Scopus databases (from the databases’ inception up to               • Total dystrophic onychomycosis (TDO): 266, 14.1%
October 30, 2021) to identify eligible contributions. The
­                                                                   • Mixed pattern (MO): 51, 2.7%
following search strategy was used: (“onychomycosis”                • Endonyx onychomycosis: 2 cases
OR “Tinea unguium” OR “nail fungal infection”) AND
(“­
  onychoscopy” OR “dermatoscopy” OR “Dermoscopy”                       Methods to diagnose onychomycosis were described in
OR “videodermatoscopy” OR “videodermoscopy”).                       27 of the included papers. The diagnosis was based on KOH
    Two dermatologists (N.L. and E.M.) independently                examination [4,7,11,16,17,23,27–32,35], fungal culture
screened titles and abstracts for eligibility. Only papers in the   [2,3,5,8,13,16,19,20,24,25,33,34], and/or histologic exam-
English language were considered for inclusion. Editorials,         ination of nail plates [5,8,10,19,20,24].
commentary, and review articles were excluded. All contri-             The dermoscopic features of onychomycosis are summa-
butions reporting one or multiple cases of onychomycosis            rized in Table 2. The most common onychoscopic signs were:
and describing its dermoscopic features were included. Ref-
erence lists of included articles were further screened for ad-     Ruin Appearance
ditional eligible publications. Any discrepancy between the         Ruin appearance refers to the distal part of the thickened
2 authors (N.L. and E.M.) was resolved by consensus. Each           nail plate showing ventral indentations caused by dermal




2                                                                                Review | Dermatol Pract Concept. 2023;13(1):e2023072
                                                       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 of the subungual area under the distal margin of the
 hyperkeratosis                                            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/          A nonlinear border at the proximal edge of an onycholysis area,
                         spiked pattern                    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                                          Refers to the distal pulverization of the nail plate17,23,29
 termination
 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                  Structureless pigmentation of the nail plate
                         homogenous pattern
                         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                                         Nail matrix pigmentation detected through a relatively translucent
 sign                                                      cuticle at the proximal nail fold.4




Review | Dermatol Pract Concept. 2023;13(1):e2023072                                                                                3
                       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



debris (Figure 2a) [19]. It corresponds to the fungal presence        The frequency of linear edge in OM varied between 2%
in the nail plate [19,26]. For some authors, “ruin appear-         and 22% (a mean of 8%) and it is thought to be secondary
ance”, “distal irregular termination” [30], and “subungual         to trauma preceding OM [36].
hyperkeratosis” [19,32] can be used interchangeably. The
frequency of ruin appearance varied between 13% and                Spikes
100% (a mean of 68%) [2,7,8,12,19–23,26,29,30,34].                 “Spiked pattern”, “intermittent spiked pattern” and “Jagged
    Ruin appearance was significantly associated with DLSO         edge with spikes” share the same definition. It is character-
and never described in SO and endonyx onychomycosis                ized as indentations at the proximal edge of the onycholy-
(Table 3).                                                         tic area (Figure 2c) [23]. These structures correspond to the
                                                                   distal-to-proximal invasion of the nail bed’s longitudinal
Longitudinal Striae:                                               ridges by dermatophytes [3,11,23]. The frequency of jagged
Longitudinal striae appear as streaks within the nail plate        edges with spikes varied between 39% and 100% (a mean of
and are the result of the fungal invasion of the nail plate        58%) [3,5–9,12–15,17–21,24,29–34,36]. These structures
(Figure 2b) [26]. They were reported in 64.9% of cases.            were significantly associated with DLSO, very frequent in
    Longitudinal striae are very frequent in DLSO, TDO, and        TDO, and never described in SO, PSO and endonyx onycho-
rarely reported in SO (p=0.001), and PSO (p=0.03).                 mycosis (Table 3).
                                                                      Spikes can also be seen in onychorrhexis, but are located
Onycholysis                                                        in the proximal part of the nail [11,26]. Spikes help differen-
Onycholysis is the separation of the nail plate from the nail      tiate onycholysis related to trauma and onychomycosis. The
bed. According to Zaias et al, the main etiology of onycholysis    former is virtually never associated with spikes.
is trauma and onychomycosis is never the initiating factor [36].
    Dermoscopy helps differentiate onycholysis of traumatic        Chromonychia
origin from onychomycosis. A linear edge at the proximal           Chromonychia is defined as a discoloration of the nail
aspect of onycholysis is associated with trauma, while spikes      plate. It may be secondary to colony formation, flakes, or
are associated with onychomycosis (Figure 2c) [23]. In on-         subungual debris [15,23,26]. The colors ranged from white
ychomycosis, the frequency of onycholysis varies between 5         (leukonychia), green, yellow, brown, gray, and black. The
and 100% (a mean of 65%).                                          prevalence of chromonychia varies between 22 and 100%



4                                                                             Review | Dermatol Pract Concept. 2023;13(1):e2023072
 IDENTIFICATION         IDENTIFICATION OF STUDIES VIA DATABASES (PUBMED AND SCOPUS)




                   RECORDS IDENTIFIED FROM
                   DATABASES (n=180)




                   RECORDS AFTER DUPLICATES
                   REMOVES (n=113)
 SCREENING




                                                                   RECORDS EXCLUDED
                   REPORTS SCREENED
                                                                   (n=36): EDITORIALS, REVIEWS, COMMENTARY
                   (n=113)
                                                                   (n=32): NOT RELEVANT




                   FULL-TEXT ARTICLES ASSESSED
 ELIGIBILITY




                   FOR ELIGIBILITY (n=45)                          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)




                   STUDIES INCLUDED IN QUALITIVE
                   SYNTHESIS (n=33)
 INCLUDED




                  STUDIES INCLUDED IN
                  QUANTITATIVE SYNTHESIS (n=33)



Figure 1. Flow diagram.




(a mean of 70.4%). The most frequent color was yellow          Leukonychia:
(a mean of 57%) [4,8,9,13,14,16,19,20,28–32,34,36,37].         Leukonychia is a white coloration of the nail. It is explained by
          The association of chromonychia of multiple colors   the fungal growth in the nail plate, similar to the growth in the
with longitudinal striae, spikes, and onycholysis creates a    culture medium [19]. It can be punctate, transverse (Figure 2d),
pattern called “aurora borealis” or “aurora sign” (Figure 3)   or homogenous (Table 1). The frequency of leukonychia var-
because they resemble waves of northern lights or aurora       ies between 2% and 75 % (a mean of 37%) [2,6,19,20,29].
­borealis [30].                                                Leukonychia was significantly associated with SO (p<0.001).



Review | Dermatol Pract Concept. 2023;13(1):e2023072                                                                          5
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                                                  (Figure 4). However, in nail melanomas, the pigmentation
Fungal melanonychia is a dark pigmentation of the nail plate.        is wider in the proximal portion, resulting in a triangular
It is explained by the synthesis of melanin by some fungi. The       melanonychia [30].
best-characterized fungal melanin is 1,8-­dihydroxynaphthalene
(DHN) melanin. Its biosynthetic pathway is called the pen-           Splinter Hemorrhage
taketide pathway. The name “Pentaketide” derives from the            Splinter hemorrhages are linear hemorrhages caused by
fact that the naphthalene ring structure, that underlies the         bleeding capillaries[16]. It is a common yet nonspecific sign
DHN-melanin pathway is formed by the binding and cycliza-            of onychomycosis. It is reported in association with trauma
tion of five subunits of a ketone compound derived from five         and psoriasis[25]. The prevalence of splinter hemorrhage in
acetate molecules. Fungal melanin protects the fungus from           onychomycosis varies between 2% and 25% (a mean of 5%)
the aggressions of the environment [37].                             [11,17,19,21,34,36].
    Dermoscopy helps distinguish fungal melanonychia from
nail melanoma, nail matrix nevus, and melanocytic activa-            Sensitivity and Specificity of the Dermoscopic Signs
tion [4,5,7,9]. Yellow and red discoloration are significantly       of Onychomycosis:
associated with fungal melanonychia, while the triangular            Several studies compared the dermoscopic features of
sign and Hutchinson sign are features of nail melanoma and           onychomycosis, psoriasis, and traumatic nail dystrophy
never described in association with onychomycosis (Table 4).         [3,8,11,12,25]. The sensitivity and specificity of the dermo-
Conversely, distal linear and reverse triangular patterns are        scopic signs of onychomycosis are summarized in Table 5.
signs of fungal melanonychia (Table 4). Indeed, in fungal            Overall the sensitivity of “ruin appearance”, “longitudi-
melanonychia, the pigmentation is wider at the distal por-           nal striae”, and “spikes” are low with good specificity
tion of the nail due to the distal-to-proximal progression of        (­Table 5). The “Aurora borealis” sign showed the highest
fungi which is responsible for the reverse triangular pattern        sensitivity and specificity. Some dermoscopic signs were only



6                                                                                Review | Dermatol Pract Concept. 2023;13(1):e2023072
                                                                                         Table 3. Dermoscopic aspects and their association with clinical subtypes of onychomycosis.
                                                                                      DLSO                    SO                       PSO                       MO                        TDO             Onychomycosis endonyx
                                                                           Frequency     P-Value     Frequency     P-Value   Frequency       P-Value   Frequency      P-Value   Frequency        P-Value   Frequency    P-Value




Review | Dermatol Pract Concept. 2023;13(1):e2023072
                                                       Ruin appearance      142/206          0.016      0/5        0.001         1/4           NS          -             -        53/55            NS         0             -
                                                       Longitudinal         326/496           NS       2/13        0.001        3/11          0.03       20/47           -       117/210           NS         2/2          NS
                                                       striae
                                                       Spikes (Jagged       403/657          0.002     4/21          NS         2/18         0.029       34/94          NS        95/259           NS         0/2          NS
                                                       edge with spikes/
                                                       Spiked pattern)
                                                       Distal irregular     154/462           NS       1/12        0.017        5/10           NS        14/47          NS       126/186           NS         0/2          NS
                                                       termination
                                                       Leukonychia           56/256          0.017      7/7        0.0001        1/7           NS        34/47          NS         0/58            NS         2/2          NS

                                                       DLSO: Distal/lateral subungual onychomycosis; MO: Mixed pattern; NS: non-significant; PSO: Proximal subungual onychomycosis (PSO); SO: Superficial onychomycosis; TDO:
                                                       Total dystrophic onychomycosis;




7
                                                                       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-
Figure 3. “Aurora borealis” sign. Chromonychia of multiple colors,     sistency between authors on the terminology to be used to
associated with onycholysis, spikes and longitudinal striae.           describe dermoscopic features of onychomycosis (Table 1).




                  Table 4. Characteristics of melanonychia in patients with onychomycosis,
                         nail matrix naevus, melanoma, and melanocytic activation.
                                                  Fungal             Nail matrix      Malignant        Melanocytic
                                               melanonychia            nevus          melanoma          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 longitudinal pattern                 57/148              26/27             17/25             24/24                1
 pattern      distal diffuse pattern                20/88                 -              6/14                 -               0.18
                  proximal diffuse                  7/88                  -              2/14                 -               0.60
                  pattern
                  distal linear pattern             7/88                  -              0/14                 -               0.58
                  total diffuse pattern             21/88                 -              5/14                 -               0.33
                  reverse triangular                19/58               0/27             1/25               0/24                1
                  pattern
                  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                 -                 -                 -                 -



8                                                                                  Review | Dermatol Pract Concept. 2023;13(1):e2023072
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                   0/37                 0/14                26/41                *                  *
 associated with onycholysis
 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



    Following the third consensus conference of the Interna-              while metaphorical terminology is memorable but incompre-
tional Society of Dermoscopy, standardization of terminol-                hensible outside its context [38]. We suggest the following
ogy in dermoscopy of cutaneous lesions was adopted [38].                  terminology for the most prevalent onychoscopic signs of
Both descriptive and metaphorical terminology was consid-                 onychomycosis:
ered acceptable for clinical use and research [38]. Similarly,
we believe that both descriptive and analytical terminology               • “ruin appearance” (metaphoric) = subungual hyperkera-
can be used to describe dermoscopic signs of onychomyco-                    tosis with distal irregular termination (descriptive)
sis. Descriptive (analytical) terminology has the advantage of            • “longitudinal striae” (descriptive)
being comprehensible and suitable for learning, and the dis-              • “spikes” (metaphoric) to replace “spiky pattern”, “Jagged
advantage of possible long descriptive complex structures,                  edge with spikes” and “spiked pattern”



Review | Dermatol Pract Concept. 2023;13(1):e2023072                                                                                9
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.


• chromonychia (descriptive): nail discoloration                      2. Litaiem N, Nakouri I, Bouhlel S, et al. Dermoscopic fea-
• leukonychia (descriptive): white discoloration of the                  tures of toenail onychomycosis. J Am Podiatr Med Assoc.
                                                                         2020;110(3):1-4. doi:10.7547/18-102
  nail plate
                                                                      3. Piraccini BM, Balestri R, Starace M, et al. Nail digital der-
                                                                         moscopy (onychoscopy) in the diagnosis of onychomycosis.
     We also suggest that the pigmentation patterns described
                                                                         2013;27(4):509-513. doi:10.1111/J.1468-3083.2011.04323.X
in Table 4 should be used as-is since these patterns are widely
                                                                      4. Ohn J, Choe YS, Park J, et al. Dermoscopic patterns of fun-
used in onychoscopic terminology and there are no related                gal melanonychia: A comparative study with other causes of
discrepancies between published articles [3–5,7].                        melanonychia. J Am Acad Dermatol. 2017;76(3):488-493.e2.
     Dermoscopy is very useful in diagnosing pigmented nails.            doi:10.1016/J.JAAD.2016.08.013
Chromonychia is very frequent in onychomycosis with yel-              5. Kilinc Karaarslan I, Acar A, Aytimur D, et al. Dermo-
                                                                         scopic features in fungal melanonychia. Clin Exp Dermatol.
low and red discoloration being significantly associated with
                                                                         2015;40(3):271-278. doi:10.1111/CED.12552
fungal melanonychia. Other signs help distinguish fungal
                                                                      6. Starace M, Ambrogio F, Bruni F, et al. Dermatophytic mela-
melanonychia from nail melanoma including distal linear and              nonychia: A case series of an increasing disease. Mycoses.
reverse triangular patterns. Conversely, the triangular pattern          2021;64(5):511-519. doi:10.1111/MYC.13237
and Hutchinson sign are features of nail melanoma [4–7,9].            7. Kim HJ, Kim TW, Park SM, et al. Clinical and Dermoscopic Fea-
     In conclusion, dermoscopy is useful in diagnosing ony-              tures of Fungal Melanonychia: Differentiating from Subungual
                                                                         Melanoma. Ann Dermatol. 2020;32(6):460-465. doi:10.5021
chomycosis. The current review provides a framework for
                                                                         /AD.2020.32.6.460
issues related to onychoscopic terminology of onychomyco-
                                                                      8. Leeyaphan C, Suphatsathienkul P, Limphoka P, et al. Sulphur
sis and is intended to serve as an aid for students, teachers,           Nuggets. Med Mycol J. 2021;62(3):21-00006. doi:10.3314
and researchers. Dermoscopic signs of onychomycosis show                 /MMJ.21-00006
good specificity and are useful in distinguishing nail psoria-        9. Elmas ÖF, Metin MS. Dermoscopic findings of fungal melanony-
sis, trauma, and onychomycosis. It helps differentiate fungal            chia. Postep Dermatologii i Alergol. 2020;37(2):180-183.
                                                                     10. Grover C, Jakhar D, Sharma S. The grid pattern of white su-
melanonychia from nail melanoma, nevi, and melanocytic
                                                                         perficial onychomycosis. Indian J Dermatol Venereol Leprol.
activation and allows precise monitoring of nail regrowth
                                                                         2020;86(5):568-570. doi:10.4103/IJDVL.IJDVL_699_19
after systemic antifungal treatment initiation (Figure 5).           11. Ankad BS, Gupta A, Alekhya R, et al. Dermoscopy of Onycholy-
                                                                         sis Due to Nail Psoriasis, Onychomycosis and Trauma: A Cross
References                                                               Sectional Study in Skin of Color. Indian Dermatol Online J.
                                                                         2020;11(5):777-783. doi:10.4103/IDOJ.IDOJ_475_19
 1. Piraccini BM, Alessandrini A. Onychomycosis: A Review. J Fungi   12. Ramos Pinheiro R, Dias Domingues T, Sousa V, et al. A com-
    (Basel). 2015;1(1):30-43. doi:10.3390/jof1010030                     parative study of onychomycosis and traumatic toenail




10                                                                               Review | Dermatol Pract Concept. 2023;13(1):e2023072
      onychodystrophy dermoscopic patterns. J Eur Acad Dermatol-                  Soc. 2015;12(3):145-149. doi:10.1097/01.EWX.0000469303
      ogy Venereol. 2019;33(4):786-792. doi:10.1111/JDV.15358                     .65552.A1
13.   Abdallah NA, Said M, Mahmoud MT, et al. Onychomycosis:                26.   De Crignis G, Valgas N, Rezende P, et al. Dermatoscopy of ony-
      Correlation between the dermoscopic patterns and fungal cul-                chomycosis. Int J Dermatol. 2014;53(2). doi:10.1111/IJD.12104
      ture. J Cosmet Dermatol. 2020;19(5):1196-1204. doi:10.1111            27.   Di Chiacchio N, Noriega LF, Gioia Di Chiacchio N, et al. Su-
      /JOCD.13144                                                                 perficial black onychomycosis due to Neoscytalidium dimidia-
14.   Bhat YJ, Keen A, Hassan I, et al. Can Dermoscopy Serve as a                 tum. J Eur Acad Dermatology Venereol. 2017;31(10):e453-e455.
      Diagnostic Tool in Dermatophytosis? A Pilot Study. 2019;10(5).              doi:10.1111/JDV.14273
      doi:10.4103/IDOJ.IDOJ_423_18                                          28.   Bet DL, dos Reis AL, Di Chiacchio N, et al. Dermoscopy and
15.   Maatouk I, Haber R, Benmehidi N. Onychoscopic evaluation of                 onychomycosis: Guided nail abrasion for mycological sam-
      distal and lateral subungual onychomycosis: A cross-sectional               ples. An Bras Dermatol. 2015;90(6):904-906. doi:10.1590/
      study in Lebanon. Curr Med Mycol. 2019;5(2):41-44.                          ABD1806-4841.20154615
      doi:10.18502/CMM.5.2.1161                                             29.   Devi Sangeetha A, Gopalakrishnan K, Ramachandran R, et al.
16.   Bhat YJ, Mir MA, Keen A, Hassan I. Onychoscopy: an observa-                 A descriptive study of onychoscopic features in various subtypes
      tional study in 237 patients from the Kashmir Valley of North               of onychomycosis. Med J Armed Forces India. Published online
      India. Dermatol Pract Concept. Published online October 31,                 2021. doi:10.1016/J.MJAFI.2021.03.019
      2018:283-291. doi:10.5826/DPC.0804A06                                 30.   Hazarika N, Chauhan P, Divyalakshmi C, et al. Onychoscopy:
17.   Chetana K, Menon R, David BG. Onychoscopic evaluation of on-                A quick and effective tool for diagnosing onychomycosis in a
      ychomycosis in a tertiary care teaching hospital: a cross-sectional         resource-poor setting. Acta Dermatovenerologica Alpina, Pannon-
      study from South India. Int J Dermatol. 2018;57(7):837-842.                 ica Adriat. 2021;30(1):11-14. doi:10.15570/ACTAAPA.2021.3
      doi:10.1111/IJD.14008                                                 31.   Sato T, Kitahara H, Honda H, et al. Onychomycosis of the mid-
18.   Nargis T, Pinto M, Shenoy MM, et al. Dermoscopic Features of                dle finger of a Japanese judo athlete due to trichophyton ton-
      Distal Lateral Subungual Onychomycosis. Indian Dermatol On-                 surans. Med Mycol J. 2019;60(1):1-4.
    line J. 2018;9(1):16-19. doi:10.4103/IDOJ.IDOJ_40_17                    32.   Yorulmaz A, Yalcin B. Dermoscopy as a first step in the di-
19. Kaynak E, Göktay F, Güneş P, et al. The role of dermoscopy in the             agnosis of onychomycosis. Postep Dermatologii i Alergol.
    diagnosis of distal lateral subungual onychomycosis. Arch Der-                2018;35(3):251-258.
    matol Res. 2018;310(1):57-69. doi:10.1007/S00403-017-1796-2             33.   Nada EE din A, El Taieb MA, El-Feky MA, et al. Diagnosis of
20. Kayarkatte M, Singal A, Pandhi D, et al. Nail dermoscopy (on-                 onychomycosis clinically by nail dermoscopy versus microbio-
    ychoscopy) findings in the diagnosis of primary onychomyco-                   logical diagnosis. Arch Dermatol Res. 2020;312(3):207-212.
    sis: A cross-sectional study. Indian J Dermatol Venereol Leprol.              doi:10.1007/S00403-019-02008-6
    2020;86(4):341-349. doi:10.4103/IJDVL.IJDVL_100_19                      34.   González Cortés LF, Prada L,et al. Onychoscopy in a Colombian
21. Bodman MA. Point-of-care diagnosis of onychomycosis by                        population with a diagnosis of toenail onychomycosis: an eval-
    dermoscopy. J Am Podiatr Med Assoc. 2017;107(5):413-418.                      uation study for this diagnostic test. Clin Exp Dermatol. Pub-
    doi:10.7547/16-183                                                            lished online 2021. doi:10.1111/CED.14706
22. Kallis P, Tosti A. Dermoscopy as a first step in the diagnosis of       35.   Campos S, Lencastre A. Dermatoscopic Correlates of Nail Appa-
    onychomycosis. 1(4). doi:10.1159/000445908                                    ratus Disease: A Look at the Nail From Another Scope, the Der-
23. Jesús-Silva MA, Fernández-Martínez R, Roldán-Marín R, et                      matoscope. Imaging in Dermatology. Published online August
    al. Dermoscopic patterns in patients with a clinical diagno-                  19, 2016:43-58. doi:10.1016/B978-0-12-802838-4.00005-4
    sis of onychomycosis-results of a prospective study including           36.   Zaias N, Escovar SX, Zaiac MN. Finger and toenail onycholy-
    data of potassium hydroxide (KOH) and culture examina-                        sis. J Eur Acad Dermatology Venereol. 2015;29(5):848-853.
    tion. Dermatol Pract Concept. 2015;5(2):39-44. doi:10.5826                    doi:10.1111/JDV.12862
    /DPC.0502A05                                                            37.   Jin H, Kim JM, Kim GW, et al. Diagnostic criteria for and clinical
24. El-Hoshy KH, Abdel Hay RM, El-Sherif RH, et al. Nail der-                     review of melanonychia in Korean patients. J Am Acad Derma-
    moscopy is a helpful tool in the diagnosis of onychomycosis:                  tol. 2016;74(6):1121-1127. doi:10.1016/J.JAAD.2015.12.039
    A case control study. Eur J Dermatology. 2015;25(5):494-495.            38.   Kittler H, Marghoob AA, Argenziano G, et al. Standardization
    doi:10.1684/EJD.2015.2637                                                     of terminology in dermoscopy/dermatoscopy: Results of the
25. Elfar NN, Abdel-Latif AM, Labeh EA. Role of onychoscopy in                    third consensus conference of the International Society of Der-
    differentiation between distal subungual onychomycosis, psoria-               moscopy. J Am Acad Dermatol. 2016;74(6):1093. doi:10.1016/J
    sis, and traumatic onycholysis. J Egypt Women’s Dermatologic                  .JAAD.2015.12.038




Review | Dermatol Pract Concept. 2023;13(1):e2023072                                                                                            11
