Dermoscopic Features of Psoriatic Nails and Their Correlation to Disease Severity

Background Nail psoriasis is a challenging chronic condition affecting patients functionally and psychologically. Nail involvement is observed in 15–80% of psoriatic patients with occasional presence of isolated nail psoriasis. Objectives To evaluate dermoscopic features of nail psoriasis and correlate them clinically. Methods The study included fifty subjects with nail psoriasis. Psoriasis skin and nail severity was evaluated using psoriasis area severity index (PASI) and nail psoriasis severity index (NAPSI). Dermoscopy of the nails (onychoscopy) was performed, and features were recorded and analyzed. Results The most common clinical and dermoscopic findings were pitting (86%) and onycholysis (82%). Among all dermoscopic features of nail psoriasis, only longitudinal striations and subungual hyperkeratosis were significantly higher in patients with moderate to severe psoriasis than in patients with mild psoriasis (P=0.028; P=0.042, respectively). PASI scores correlated positively but none significantly with NAPSI scores (r = 0.132, P=0.360), and similarly, no significant correlation was observed between the duration of psoriasis and the dermoscopic NAPSI (r = 0.022, P=0.879). Conclusion Dermoscopy can serve as a useful tool for early diagnosis of psoriatic nail changes not always visible to the naked eye and is a non-invasive easy-to-use confirmatory tool for nail changes in psoriatic disease or in isolated nail involvement.


Introduction
Psoriasis represents a chronic skin condition afecting 1-2% of world population [1]. Furthermore, nail involvement in psoriasis afects approximately 15-80% of cases. Only 5% of psoriatic patients present with isolated nail changes with no skin involvement [2].
A wide range of psoriatic nail clinical presentations can be identifed based on the site of anatomical afection (nail matrix/nail bed) [3]. Nail matrix involvement presents as pitting, leukonychia, and crumbling as well as predominant red spots that can be seen in the lunula. On the other hand, nail bed afection can manifest with an array of presentations as subungual hyperkeratosis, splinter hemorrhages, and onycholysis [4].
Far beyond a cosmetic disfgurement, nail involvement also leads to substantial disease burden as well as impaired daily activity and stigmatization. Moreover, nail afection can be a marker of disease severity and a prognostic factor for disease progression into psoriatic arthritis [5].
Diagnostic biopsy remains to be the gold standard of diagnosing nail psoriasis, yet it remains to be painful. Dermoscopy is a non-invasive tool whose scope has extended beyond its initial use in cutaneous melanoma to become an adjunctive tool in diagnosing many pigmented and non-pigmented skin diseases including nail disorders which is termed as onychoscopy [4,5].
Te aim of this study was to evaluate the dermoscopic nail features in psoriatic nails, comparing the dermoscopic examination with clinical examination to determine the correlation between the dermoscopic nail features and the disease severity using psoriasis area severity index (PASI) score and nail psoriasis severity index (NAPSI) score.

Patients and Methods
Tis cross-sectional study was performed during the period between April 2021 and December 2021 on ffty (50) patients diagnosed clinically with psoriasis with nail involvement to detect the dermoscopic nail features among them. Ethical committee approvals were obtained in advance, and included patients were instructed on the study procedures and consented if willing to participate. Te study was approved by the Ethics Committee of Damietta Faculty of Medicine IRB (00012367-22-34-110), Al-Azhar University, Egypt.
Patients who fulflled inclusion crieteria of the study had a full personal and clinical history examination. Demographic data, disease onset and duration, and any associated comorbidities were all recorded. KOH mounts obtained from nail clippings were performed to diagnose and exclude any subjects with onychomycosis. Patients complaining of erythrodermic form of psoriasis or sufering from systemic diseases afecting nails were excluded. Similarly, pregnant or lactating females were excluded from the study.
To determine psoriasis disease severity, the whole body was divided into four sections (head (H) (10% of a person's skin); arms (A) (20%); trunk (T) (30%); and legs (L) (40%)) that when added up provided a fnal PASI score. A score of 72 is the highest that could be achieved and demonstrates a 100% body afection with psoriasis while zero (0) score is the lowest that can be achieved and demonstrates no skin involvement. PASI scores can be divided into mild (below 10); moderate (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20); and severe if above 20 [6]. Te NAPSI scoring system was used to evaluate psoriatic nail afection after thorough clinical and dermoscopic evaluation of nails. To calculate NAPSI, each nail was divided into 4 equal and symmetrical quadrants to properly assess nail matrix and nail bed changes. Each nail matrix and nail bed change was given a score of 1 if present and zero (0) if absent. A score of 1 is given for the presence of such signs in every quadrant, so that there is a nail matrix score of 0-4 and nail bed score of 0-4 per nail with a minimum score of 0 and a maximum score of 8 per nail. Any additional nail changes were also recorded [5].
Dermoscopic images were captured with a DermLite DL4, ×10 dermoscope using polarized and non-polarized modes. Digital photography using the mobile camera (48MP) was used for recording micro-and macroimages.

Statistical Analysis.
Following the conduction of the study and provision of results, analysis was reproduced using SPSS 27 package. Standard deviation, median data, and Pearson chi-square descriptive statistics were calculated and analyzed and summarized to compare between the diferent groups on basis of qualitative variables provided and reproduce any statistical signifcance. Fisher's test was used instead of chi-squared (χ 2 ) test when the assumption that at least 80% of the expected frequencies are greater than fve was violated. On the other hand, correlation analysis was reproduced using the Spearman coefcient (rs) to indicate and highlight any signifcant association of variables used.

Results
Tis study included 50 patients with psoriasis. Teir mean age was 44 ± 18.62 years. Among the cases, 41 were males (82%) and 9 were females (18%). Te mean duration of the disease was 11.78 ± 11.14 years, and the median of cutaneous psoriasis duration was 9 years.
Te mean PASI score in the included cases was 11.57 ± 7.78 while the mean NAPSI score in the included cases was 30.66 ± 13.67. Twenty-three cases (46%) sufered from mild psoriasis while 27 cases (54%) complained of moderate to severe activity (Table 1).
When checking all dermoscopic features of nail psoriasis recorded, only the longitudinal striations and subungual hyperkeratosis were signifcantly higher in subjects with moderate to severe psoriasis when compared to those with mild psoriasis (P � 0.028; P � 0.042, respectively) ( Table 3).

Discussion
Dermoscopy is a non-invasive easy-to-use tool used for diagnosis and follow-up of many skin diseases [7]. Despite histopathology being the golden diagnostic tool in psoriasis, dermoscopy of nails (onychoscopy) can serve as an efcient tool for visualisation, confrmation, and follow-up of patients with nail psoriasis [8].
So far, there is a paucity of studies observing the features of nail psoriasis and correlating them to disease severity and there is no consensus for using this efcient tool in diagnosing and follow-up of nail psoriasis lesions [9].
Pitting (n � 43; 86%) was the most common dermoscopic fnding observed in the current study. Pitting can be appreciated and seen clinically as shallow dents on the nail plate which form due to parakeratosis of the matrix while dermoscopically, it can be seen as punctuate dents surrounded by a white hue [2]. Within the same context, Khopkar and Yadav [10] and Chauhan et al. [11] disclosed that pitting was the commonest of all dermoscopic features seen in their relevant studies. Moreover, another study determined pitting to be the most reliable and third most common clinical fnding among psoriatic patients [2] ( Table 4).

Dermatology Research and Practice
Separation of the nail plate and nail bed is often referred to as onycholysis [12]. A linear erythematous border around the onycholytic areas can be specifcally seen by dermoscope which is rarely observed by the naked eye and can be considered a specifc onycholysis fnding in psoriatic nails [13].
In the current study, onycholysis was the second most common fnding and detected in 41 cases (82%). In agreement with our fndings, Khopkar and Yadav [10] showed that onycholysis was the second most dermoscopic fnding in patients sufering from nail psoriasis and recorded the observation in 10 out of 46 patients. Also, Polat and Kapıcıoglu [2] determined the incidence of onycholysis by dermoscopy to be 77.5%, ranking the third most common fnding among their study participants. Long et al. [14] reported onycholysis to be the commonest fnding among their study participants while Wanniang et al. [4] discovered onycholysis in 54% of cases sufering from nail psoriasis in their study.
Salmon patches, also known as the oil drop sign, refer to the yellowish-red discoloration that appear as irregular translucent areas visible through the nail plate. In the current study, salmon patches were a common fnding and seen in 23 cases (46%). Tis was in accordance with other studies that dermoscopically observed salmon patches in 47.5% and 44% of patients, respectively [2,4].
In the current study, longitudinal striations were reported in 32 cases (64%). Tis was in agreement with Chauhan et al. who showed that longitudinal ridging could be appreciated in 57.3% of fngernails and 22.7% toenails [11].
Splinter hemorrhages were dermoscopically detected in 52% of cases in this study while a higher incidence of 62%, 73.1%, and 80% was reported by other authors [2,4,5].
Leukonychia is due to the inclusion of parakeratotic cells in the nail from lesions in the matrix [15]. In the current study, leukonychia was reported in 13 cases (26%) similar to the fnding of Waaniang who detected leukonychia among 22% of their studied cases (n � 50) [4].
Subungual hyperkeratosis was the second most common nail bed dermoscopic fnding in our study and signifcantly correlated with disease severity (P � 0.042) while in the study conducted by Chauhan et al., it was the most common nail bed dermoscopic fnding in both fngernails and toenails [11].
In the current study, there was a weak non-signifcant correlation between NAPSI and PASI (r � 0.132, P � 0.360). Our fndings matched fndings by Wanniang, Long, and Arora who reported a positive correlation between the total NAPSI score and PASI score (r � 0.535, P < 0.001; r � 0.9013, P < 0.05; r � 0.56, P < 0.001, respectively) [4,15,16]. Such fnding anticipates that nail afection is probably higher with severe forms of systemic infammation; however, this could be biased by the fact that some dermoscopic features of nail afection still persist after remission of activity in some patients [4,15,16].
Te current study demonstrated a weak non-signifcant correlation between NAPSI and psoriasis duration (r � 0.022, P � 0.879). In the study conducted by Wanniang et al., a weak correlation was observed between the duration of psoriasis and the dermoscopic NAPSI score (r � 0.2835; P � 0.046). Tey speculated that duration of cutaneous psoriasis is associated with longer and more severe afection of nail psoriasis [4]. No statistically signifcant diference was noted in the distribution of nail psoriasis between the cases with mild psoriasis and cases with moderate to severe psoriasis except for longitudinal striations and subungual hyperkeratosis which were signifcantly higher in the moderate to severe psoriasis group (P � 0.028; P � 0.042, respectively).
To date, reports on dermoscopic features of nail psoriasis in relation to disease severity were few and the existing data were not conclusive. In one study, dilated capillaries, Continuous data are expressed as mean ± SD and median (range). Categorical data are expressed as number (%). thickening of the nail plate, subungual hyperkeratosis, and pitting were found to be associated with higher disease severity [17] while in another study, red lunula and longitudinal fssures were more relevant to the severity of psoriasis [15]. Te small study sample represents a limitation besides the inability to investigate the dermoscopic fndings of nail psoriasis in other subtypes of psoriasis not included in this study. Lack of toe nail assessment represents another limitation of the study as well as the male to female pattern of inclusion. Furthermore, there was no control and no assessment of dermoscopic changes after treatment.
In conclusion, dermoscopy can serve as a useful tool for early diagnosis of psoriatic nail changes not always visible to the naked eye and is a non-invasive easy-to-use confrmatory tool for nail changes in psoriatic disease or in isolated nail involvement.
A hallmark advantage of dermoscopy is its ability to interface between histopathologic and clinical examinations as well as its ability to aid in early diagnosis of nail afection even before clinical signs are evident. Taking into consideration this advantage of early dermoscopic features in clinically uninvolved nails, dermoscopy can be used as a marker of disease activity and progression. Tis study comprehensively describes the dermoscopic features of diferent parts of nail unit in patients of nail psoriasis. Larger sample size and evaluation of diferent types of psoriatic nail changes before and after treatment are required to elucidate distinct relationships between dermoscopic changes and disease severity.

Data Availability
Te data used to support the fndings of this study are available from the corresponding author upon request.

Conflicts of Interest
Te authors declare that they have no conficts of interest.