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Role of onychoscopy in differentiation between distal subungual onychomycosis, psoriasis, and traumatic onycholysis

Elfar, Nashwa N.a; Abdel-Latif, Amany M.a; Labeh, Eman A.b

Journal of the Egyptian Women's Dermatologic Society: September 2015 - Volume 12 - Issue 3 - p 145–149
doi: 10.1097/01.EWX.0000469303.65552.a1
Original articles

Background Dermoscopy is helpful in the diagnosis of numerous nail diseases.

Objective To describe the specific dermoscopic signs for psoriasis, traumatic onycholysis, and distal subungual onychomycosis.

Patients and methods The study was carried out on 39 patients with distal subungual onycholysis. Dermoscopic imaging and mycological examination (microscopic examination with 20% KOH and culture on Sabouraud’s dextrose agar) were carried out. The final mycological results were correlated with the detected dermoscopic features.

Results In mycologically positive patients, confirmed as positive by means of both microscopic examination and fungal culture, the most common and specific dermoscopic features were longitudinal striae and jagged edge with spikes of the proximal margin of the onycholytic nail. In mycologically negative traumatic onycholysis, the most common and unique feature was linear edge without spikes of the proximal margin of the onycholytic nail; however, in dermatophyte-negative psoriasis, the most specific feature was the erythematous border.

Conclusion Longitudinal striae and jagged edge with spikes patterns were distinctive dermoscopic signs, exclusive to distal subungual onychomycosis. Dermoscopy should be considered a helpful, quite simple, quick, and inexpensive technique for diagnosis and differentiation between distal subungual onychomycosis, psoriasis, and traumatic onycholysis.

Departments of aDermatology and Venereology

bMedical Microbiology and Immunology, Faculty of Medicine, Tanta University, Tanta, Egypt

Correspondence to Nashwa N. Elfar, MD, Department of Dermatology & Venereology, Faculty of Medicine, Tanta University, Tanta, Egypt Tel/fax: +20 403 418 800; e-mail:

Received September 22, 2014

Accepted June 20, 2015

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Dermoscopy can be used to evaluate the nail apparatus (i.e. onychoscopy), and it is a useful tool for elucidating common findings about specific nail diseases to reinforce presumptive clinical diagnoses and guide the management and prognoses of different onychopathies 1,2.

Onychomycosis is a fungal infection of the nail plate or nail bed, leading to the gradual destruction of the nail plate. It has been referred to be the most prevalent among nail disorders and accounts for about 50% of all diseased nails 3. Distolateral subungual onychomycosis (DSO) is the most common form of onychomycosis. Infection progresses mainly to the matrix from the distal to the proximal, through the distal–lateral margins, or through the lateral groove of the nail plate, beginning at the hyponychium 4.

There is a wide range of potential differential diagnoses for onycholysis, the most important of which are onychomycoses and nail dystrophies after minor trauma. Furthermore, it is possible that both onychomycosis and psoriasis are present in the same individual in different digits, as well as in the same nail. This may render the differential diagnosis between these frequent nail conditions very difficult if not impossible without mycological and/or histopathological examinations, which are time-consuming 5. Therefore, this work aimed to describe the specific dermoscopic signs for psoriatic onycholysis, traumatic onycholysis (TO), and distal subungual onychomycosis, to facilitate their differentiation.

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Patients and methods

The present study was conducted on 39 patients with distal subungual onycholysis, attending the Outpatient Clinic of Dermatology and Venereology, Department of Tanta University Hospital, during the period from August 2012 to July 2013. The study was approved by the Research Ethics Committee of Faculty of Medicine, Tanta University. All participants gave informed consent before participation in the study.

Patients who were included in the study were those with different common causes of distal subungual onycholysis, such as onychomycosis, trauma, and psoriasis. The diagnosis of psoriasis was achieved clinically and all of them had cutaneous and nail psoriasis. History of trauma in TO patients was positive. Patients had more than one affected nail.

Patients who were excluded from the study included those with a history of systemic illness and patients who had undergone systemic or topical treatment for their nails in the past 3 months. All patients were subjected to the following:

  • Complete history taking, including past history of nail trauma.
  • General and dermatological examination.
  • Digital photographic imaging for the diseased nails. Images were obtained using a digital camera (Sony Cybershot DSC-W320/W330, ×4 optical zoom, 14.1 Megapixels; Sony Corporation, Tokyo, Japan) that produced imagery with a magnification of 30-fold through its three-fold optical zoom lens. In each patient, several different images at 10- to 30-fold magnifications were taken and evaluated.
  • Digital dermoscopic imaging: The dermoscopy used in this study was Dermlite II PRO HR (3 Gen Inc., San Juan Capistrano, California, USA), which is palm-sized, offers high light output, has a large 25 mm lens, camera adaptability (using the previous digital camera), as well as an integrated rechargeable lithium ion battery. It combines polarized and immersion fluid. The unit is equipped with a retractable faceplate spacer. As regards the light intensity, a push button is used to toggle between two light intensity settings. The first mode activates 16 LEDs and the second activates 32 LEDs. Ultrasound gel was applied on the affected nail before examination and then the dermoscope was applied with a space of about 1 mm between it and the nail, and the magnification power was ×10;
  • Laboratory investigations: The nail was cleaned with 70% alcohol and then the infected nail was clipped proximally and the nail bed and subungual debris were scraped with a serrated curette. All specimens were examined by means of direct microscopy with 20% potassium hydroxide (KOH) and by means of fungal culture on Sabouraud dextrosr agar medium. The plates were incubated at 27°C for up to 4 weeks and examination of fungal colonies on different plates was carried out. Microscopic examination of the suspected colonies was performed to distinguish the fungal elements. The final mycological results were correlated with the detected dermoscopic features.
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Statistical analysis

Statistical presentation and analysis of the present study was carried out using statistical package for Microsoft Windows (SPSS Inc., Chicago, Illinois, USA). Continuous variables are presented as means±SD and discrete variables are shown as percentages. Both w2 and Fischer w2 testing were used for intergroup comparisons, and P value less than 0.05 was considered significant.

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The study included 39 patients with fingernail distal subungual onycholysis.

Most of our patients (31; 79.49%), had only affected fingernails, whereas eight patients (20.51%) had very mildly affected toenails. The duration of their illness ranged from 1 month to 2 years. The patients were classified into two groups: group I and group II. Group I included the mycologically positive group, which was confirmed by means of both microscopic examination with KOH and fungal culture. It included 24 (61.5%) patients, nine male (37.5%) and 15 female (62.5%). Their ages ranged between 25 and 65 years with a mean age of 47±12.459 years. As regards the clinical diagnosis of the studied patients, there were 17 patients (43.59%) with DSO and seven patients (17.95%) with dermatophyte-positive psoriasis.

Group II included the mycologically negative group, for which both the microscopic examination with KOH and the fungal culture revealed negative results for fungal infection. It included 15 (38.5%) patients with mycologically negative onycholysis, 10 male (66.67%) and five female (33.33%). Their ages ranged between 5 and 73 years with a mean age of 41±20.193 years. As regards the clinical diagnosis of the studied patients, there were nine patients (23.08%) with TO and six patients (15.38%) with dermatophyte-negative psoriasis.

Different fungi were detected by means of fungal culture. In group I, Aspergillus niger (Fig. 1a) was detected in two cases (8.3%), Candida albicans (Fig. 1b) was detected in seven cases (29.17%), and Trichophyton (T) spp. were detected in 15 cases (62.5%) and included 14 cases (58.33%) of Trichophyton rubrum (Fig. 1c) and one case (4.17%) of Trichophyton mentagrophyte (Fig. 1d).

Figure 1

Figure 1

The dermoscopic patterns detected in relation to the clinical and mycological diagnosis of the studied patients are presented in Table 1. In group I, longitudinal striae and jagged edge with spikes patterns were exclusive. In DSO patients (Fig. 2a), longitudinal striae were found in 16/17 patients (sensitivity was 94.12%), jagged edge with spikes was found in 13/17 patients (sensitivity was 76.47%), dot pattern was found in 1/17 patient (sensitivity was 5.88%), and splinter hemorrhage was found in 2/17 patients (sensitivity was 11.76%). In dermatophyte-positive psoriasis patients (Fig. 2b), longitudinal striae were found in 7/7 patients (sensitivity was 100%), jagged edge with spikes was found in 7/7 patients (sensitivity was 100%), dot pattern was found in 1/7 patient (sensitivity was 14.29%), and splinter hemorrhage was found in 1/7 patient (sensitivity was 14.29%), whereas the linear edge and the erythematous border patterns were absent in both DSO and dermatophyte-positive psoriasis patients. There was a statistically significant relation to jagged edge with spikes and longitudinal striae in patients with DSO and dermatophyte-positive psoriasis.

Table 1

Table 1

Figure 2

Figure 2

In group II, ‘linear edge’ without spikes and erythematous border patterns were exclusive. In TO patients (Fig. 2c), linear edge without spikes was found in 9/9 patients (sensitivity was 100%), dot pattern was found in 4/9 patients (sensitivity was 44.44%), and splinter hemorrhage was found in 2/9 patients (sensitivity was 22.22%). There was a statistically significant relation to linear edge in patients with TO (P<0.001). In dermatophyte-negative psoriasis patients (Fig. 2d), erythematous border was found in 3/6 patients (sensitivity was 50%) and splinter hemorrhage was found in 2/6 patients (sensitivity was 33.33%).

There was statistically significant relation to erythematous border in patients with dermatophyte-negative psoriasis.

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In psoriasis, the development of distal or lateral nail bed ‘oil drop’ patches and desquamation of parakeratotic cells at the hyponychium may cause nail plate separation (onycholysis). The yellow color of the onycholytic nail results from the combination of air between the nail bed and dislodged nail plate and from the accumulation of keratinocytes. The undersurface of the nail plate retains nail bed cells 6. Distal subungual onychomycosis and TO have the same symptoms, such as onycholysis and subungual hyperkeratosis, and differential diagnosis requires mycological examinations, which are time-consuming and may be false-negative in up to 35% of cases 7,8. The use of dermoscopy in nail disorders is initially used for the study of nail pigmentations. Nail dermoscopy has gradually become more and more frequently utilized to observe neoplastic and non-neoplastic nail disorders 9.

In the current study, as regards culture examination of the studied nail specimens, T. rubrum was the most isolated fungus (14 cases; 58.33%) and T. mentagrophyte was the least isolated (one case; 4.17%) in group I (mycologically positive). Candida was isolated in seven cases (29.17%); all of them were Candida albicans. Aspergillus spp. was isolated in two cases (8.3%) and all of them were Aspergillus niger. Our findings were consistent with those of Tan 10, who identified dermatophytes to be the most common organism causing onychomycosis. Moreover, Gupta and Ricci 11 showed that T. rubrum and T. mentagrophyte were the causative agents in more than 90% of all cases of onychomycosis. Dermatophytes appear to be the chief organisms capable of primary attack of the nail; consequently, the majority of cases were clearly caused by dermatophytes 12.

In the current study, T. rubrum was the only detected fungi in cases of mixed nail psoriasis and onychomycosis. This was agreement with that found by Hryncewicz-Gwo¢z¢dz¢ et al.13, who suggested a high rate of isolation of dermatophytes in psoriatic nails with onychomycosis. In addition, Kaur et al.14 concluded that nail psoriasis constituted a risk factor for onychomycosis specifically by dermatophytes. Both psoriasis and onychomycosis are common diseases in the general population. It is possible that in some patients the two diseases coexist 15. However, Larsen et al.16 stated that yeast and not dermatophytes are more frequently isolated from nails damaged by psoriasis. Ständer et al.17 reported a higher probability of yeast infection in the nail psoriasis. This is, most probably, a secondary colonization of already predamaged nail plate.

As regards the different dermoscopic patterns of distal subungual onycholysis in the current study, longitudinal striae and jagged edge with spikes patterns were exclusive in group I. This is in agreement with that reported by Piraccini et al.7, who reported that these three dermoscopic findings have a 100% specificity for DSO. The jagged edge and the sharp longitudinal indentations correspond with the proximal progression of the fungi.

De Crignis et al.18 performed a dermoscopic study in a series of 502 cases in Brazil. Distal and lateral onychomycosis were present in 336 cases (66.93%). Distal-to-proximal subungual longitudinal spikes corresponded with the onset of fungal invasion. They were justified by the anatomy of the nail unit, because the nail bed is made of longitudinal growth due to the elongated dermal papilla. The nail plate that covers the nail bed has a region of enhanced adherence in the posterior surface, corresponding to the top of the dermal papilla, and a region of reduced adherence, which corresponds to the crests of these papillae. Longitudinal spikes may be found in brittle nail syndrome, also known as onychorrhexis. However, they are not observed on the nail surface and usually start from the proximal region, going toward the distal region, a different aspect from that of onychomycosis longitudinal spikes, which are located on the subungual region and start from the distal portion of the nail plate in distal–lateral subungual onychomycosis.

In group II (mycologically negative cases), linear edge without spikes and erythematous border patterns were exclusive. Linear edge without spikes pattern was found in nine cases (100%) of TO. This was in agreement with the finding of Piraccini et al.7, who reported that the linear edge pattern was diagnostic for TO. Erythematous border was found in three cases (50%) of dermatophyte-negative PS. Nail pitting was better visualized with the help of dermoscopy as shallow pits or blackish dots.

According to Farias et al.19, when onycholysis is present, dermoscopy generally shows an erythematous border, often subclinical and invisible to the naked eye, represented by a reddish-orange stain surrounding the area of onycholysis. This finding is specific to onycholysis in nail psoriasis. Some authors consider dermoscopy to be the best tool for the diagnosis of psoriasis in patients with isolated onycholysis 20.

Splinter hemorrhage pattern was also common, although nonspecific. It was found in cases of onychomycosis, trauma, and psoriasis and appear as thin, longitudinal lines and it is a sign of capillary bleeding 19. Moreover, dot pattern was not statistically significant and not exclusive to DSO or TO. These findings were in agreement with those of Piraccini et al.7.

In conclusion, longitudinal stria and jagged edge with spikes were exclusive dermoscopic findings to distal subungual onychomycosis. Dermoscopy should be considered a helpful, quite simple, quick, and inexpensive technique for diagnosis and differentiation between distal subungual onychomycosis, psoriasis, and TO.

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Conflicts of interest

There are no conflicts of interest.

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dermoscopy; onychomycosis; subungual onycholysis

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