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REVIEW ARTICLE |
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Year : 2017 | Volume
: 4
| Issue : 2 | Page : 31-40 |
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Diagnostic utility of onychoscopy: Review of literature
Chander Grover, Deepak Jakhar
Department of Dermatology and STD, University College of Medical Sciences and GTB Hospital, New Delhi, India
Date of Web Publication | 17-Nov-2017 |
Correspondence Address: Chander Grover Professor, Department of Dermatology and STD, University College of Medical Sciences and GTB Hospital, New Delhi - 110 091 India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/ijdpdd.ijdpdd_18_17
Onychoscopy is being increasingly used as a diagnostic modality for various nail diseases. Initial research had focused mainly on nail pigmentation and nailfold capillaroscopy; however, it is now being evaluated in various infectious and inflammatory nail disorders as well. The present review aims to summarize current knowledge about onychoscopic diagnostic criteria in nail diseases. The best level of evidence attached to each indication is mentioned to answer the pertinent question: How much can we rely on onychoscopy in confirming diagnosis of nail disease?
Keywords: Dermatoscopy of nail, dermoscopy of nail, nailfold capillaroscopy, onychoscopy
How to cite this article: Grover C, Jakhar D. Diagnostic utility of onychoscopy: Review of literature. Indian J Dermatopathol Diagn Dermatol 2017;4:31-40 |
How to cite this URL: Grover C, Jakhar D. Diagnostic utility of onychoscopy: Review of literature. Indian J Dermatopathol Diagn Dermatol [serial online] 2017 [cited 2023 Mar 22];4:31-40. Available from: https://www.ijdpdd.com/text.asp?2017/4/2/31/218538 |
Introduction | |  |
There is a relative lack of diagnostic modalities which can be meaningfully used to diagnose nail disorders. Routine laboratory investigations such as potassium hydroxide examination and fungal cultures have low or variable positivity when used in the setting of nail disease as compared to skin disease.[1] Radiological imaging modalities (X-ray, ultrasound, and magnetic resonance imaging) are known to have significant limitations when used to diagnose nail diseases other than tumors.[2],[3] Nail biopsy and diagnostic histopathology are not commonly used or routinely resorted to for nail diseases; various reasons being apprehensions in the mind of patients and clinicians alike.[4] In addition, though we may consider histopathology as the diagnostic gold standard, our knowledge of diagnostic histopathological features and criteria in the setting of nail disease is far from complete.
Onychoscopy (dermatoscopy of nail) has come of age.[5] This is a diagnostic modality which is increasingly being used and evaluated by onychologists across the world.[2] Its importance is partially due to the fact that an advent of various types of dermatoscopes has facilitated easier diagnostic use in nail diseases.[5],[6] Initial studies mostly focused on nail pigmentation;[7] but as of now, onychoscopy has been evaluated in various nail diseases including infectious and inflammatory disorders.[6],[8] An additional use is nailfold capillaroscopy (NFC), used in the evaluation of systemic disease.[9],[10] The present review aims to summarize our current level of knowledge with respect to onychoscopic criteria of various nail diseases with an aim to understand if onychoscopy can replace nail biopsy in the coming future.
Materials and Methods | |  |
For the purpose of this review, we conducted a PubMed search pertaining to articles published in the English language, using the keywords “onychoscopy”, “dermoscopy of nail”, “dermatoscopy of nail”, and “nail fold capillaroscopy”. The search yielded 12, 206, 220, and 107 indexed articles, respectively. Abstracts were studied and were classified into case reports, review articles and clinical studies of various types. It was seen that the most commonly studied onychopathies were nail fold capillaroscopic abnormalities in connective tissue diseases, melanonychia, onychomycosis, and nail psoriasis. The full text versions of relevant articles (the ones offering the highest level of evidence) were downloaded and carefully evaluated. Based on this, relevant levels of evidence (LoE) were assigned to each study/report, based on the scheme proposed by Oxford Centre for Evidence-Based Medicine (OCEBM) in 2011 as outlined in [Table 1].[11] We attempted to assign the highest available LoE to the role of onychoscopy in an individual onychopathy. | Table 1: A concise account of levels of evidence as proposed by Oxford Centre for Evidence-Based Medicine in 2011*
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Nailfold Capillaroscopy (Level of Evidence-1) | |  |
The proximal nailfold (PNF) is a unique location which has horizontally oriented capillaries. This fact is used for the evaluation of alterations in the microvascular architecture. Such alterations are known to be of diagnostic as well as prognostic significance. The use of onychoscopy thus offers a distinct advantage by helping us evaluate the PNF capillary architecture reliably at higher magnification. The conditions in which NFC has been found useful are summarized below.
Raynaud's phenomenon (Level of Evidence-1)
NFC is a particularly useful diagnostic tool in differentiating primary Raynaud's phenomenon (RP) from the secondary RP.[9],[10] While the secondary RP is characterized by an abnormal capillary architecture, primary RP does not show any abnormal capillary changes.[9],[10]
Systemic sclerosis (Level of Evidence-1)
Abnormal NFC changes are now included in the revised diagnostic criteria for systemic sclerosis (SSc) (the ACR/EULAR criteria).[12] The capillary abnormalities associated with system sclerosis are termed as the “scleroderma pattern” [Figure 1]a and [Figure 1]b. Three distinct NFC patterns have been described in SSc [Table 2].[13] | Figure 1: (a) “Active” pattern of systemic sclerosis showing capillary dilation, capillary drop out and disorganization of capillary architecture (×200). (b) “Late” pattern of systemic sclerosis showing hemorrhages, few giant capillaries, avascular areas, and disorganization of capillaries (×50)
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 | Table 2: Patterns of capillary architectural alteration in systemic sclerosis
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Dermatomyositis (Level of Evidence-4)
NFC abnormalities in dermatomyositis have been defined by the presence of two or more capillary architectural changes in at least two nailfolds. The changes include capillary loop enlargement, capillary loss, disorganization of the normal distribution of capillaries, “bushy” capillaries, twisted enlarged capillaries, and capillary hemorrhages.[14] Although architectural changes may be similar to those seen in SSc, the changes are less severe and less extensive in dermatomyositis. Dermatomyositis patients have less of avascular areas, and giant capillaries; additionally, mean capillary density is higher in these patients than in those with SSc.
Systemic lupus erythematosus (Level of Evidence-4)
NFC findings in systemic lupus erythematosus are less sensitive and specific as compared to SSc. The various patterns of NFC defined in literature include morphologic changes in capillary loops and variability of capillary loop length.[15]
Mixed connective tissue disease (Level of Evidence-4)
Mixed connective tissue disease is characterized by the presence of dystrophic, extremely convoluted, branched capillary, sometimes termed a pseudoglomerular or bushy capillary formations.[16]
Diabetes mellitus (Level of Evidence-5)
Being a microangiopathy, diabetes mellitus has attracted the interest of researchers to study NFC changes associated with it. A significant number of patients have been shown to have changes in the capillary microvasculature as studied in the PNF [17] [Figure 2]. | Figure 2: Nailfold capillaroscopy in type 2 diabetes mellitus showing reduced capillary density, capillary dilation, and tortuosity (×50)
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Melanonychia (Level of Evidence-2) | |  |
Melanonychia is probably the most extensively studied entity by onychoscopy. The International Study Group on Melanonychia published the first ever evidence-based guidelines on the use of dermoscopy in the detection and management of nail pigmentation in 2013.[18] These were based on a number of studies which were reviewed.[7],[19],[20],[21],[22],[23],[24],[25],[26],[27] The salient considerations proposed are summarized below:
Technique
There was no evidence or consensus regarding which instrument or light is likely to be the most effective. Polarized and nonpolarized, as well as contact and noncontact dermatoscopes can be used. The group suggested the use of the same instrument during follow-up of the patients, preferably at a magnification of ×10. The best immersion fluid suggested was ultrasound gel.
Patterns
The group agreed that dermoscopy is useful in distinguishing the presence of blood versus melanin, on the basis of the following features which constitute a step-wise algorithm, to be followed while evaluating pigment in the nail unit.
Subungual hemorrhages
This is suggested by a pattern of globules, with or without distal streaks. It could be composed of a range of colors varying from red to brown to black [Figure 3]. However, it was emphasized that a dermoscopic diagnosis of subungual hematoma does not rule out a coexisting nail tumor, especially melanoma. | Figure 3: Subungual hematoma showing the typical globules ranging from bright red to black in color (×200)
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Benign melanonychia
The group suggested that this can be due to either melanocyte activation or melanocyte proliferation. Benign melanonychia due to melanocyte activation (ethnic or drug induced) is suggested by a homogenous gray coloration with thin, longitudinal gray lines [Figure 4]. The color can however vary depending on the pigment location and nail plate thickness. A brown background, associated with regular parallel lines of identical color, spacing and width, suggests a benign lesion (a nevus or a lentigo) [Figure 5]. At the same time, it was reported that this regular pattern may not be observed in some cases, especially in children, and rarely even in adults. | Figure 4: Thin parallel longitudinal lines uniform in color and size in benign melanonychia (×200)
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 | Figure 5: A uniform dark color band associated with regular parallel lines of identical color depicting the possibility of an underlying nevus. Furthermore, note the pseudo-Hutchinson sign in the proximal nail fold (×50)
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Malignant melanoma
A brown background with longitudinal lines that are irregular in color, width, spacing, and parallelism is suggestive of malignant melanoma. The important point is the homogeneity of color and width of each individual longitudinal line. Individual lines showing irregularity in color or width along their length raises the suspicion of a melanoma. At the same time, melanoma in adults may often show a diffuse dark background with barely visible lines. The group agreed that a dark background with areas of different hues of pigmentation is suggestive of a melanoma even in the absence of irregular lines.[18]
Nail pigment origin
Dermoscopy of the distal edge can give a clue regarding the probable origin of pigmentation within the matrix. A pigmented band presenting on the dorsal part of the nail plate probably originates from the proximal nail matrix, [Figure 6] whereas a band presenting on the ventral aspect originates from distal matrix. The group agreed that this may not be a reliable marker, especially when the nail plate is thin or has very dark or very light pigment bands. | Figure 6: Onychoscopy of the distal nail plate showing pigment band in the dorsal nail plate indicating its origin from the proximal nail matrix (×50)
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Nail fold
Dermoscopic examination of the PNF and hyponychium allows one to distinguish between benign nevi and nail melanoma (Hutchinson's or micro-Hutchinson's sign).
In the end, the study group summarized that as of now, any decision regarding the need for excision should be based on established clinical criteria and not solely on dermoscopic criteria.[18]
Onychomycosis (Level of Evidence-3) | |  |
This is one of the most common nail disorders, and many studies have focused on this indication. The disorder is classified into five types based on the pattern of invasion of the nail unit, namely, distal lateral subungual onychomycosis (DLSO), proximal subungual onychomycosis, superficial white onychomycosis, endonyx onychomycosis, and total dystrophic onychomycosis (TDO).[28] The main utility of onychoscopy is in differentiating onychomycosis from nail psoriasis and traumatic onycholysis.[8] It has been reported that the following three features are seen most commonly in onychomycosis:
- Jagged proximal edge with spikes of onycholytic edge: the proximal edge of onycholysis shows jagged margins with spikes [Figure 7].[29],[30] These jagged edges correspond to the fungal invasion in the nail plate.[31] It is mostly seen in TDO and DLSO
- Longitudinal striae/”Aurora borealis pattern:”[29] it shows the presence of multiple striae of same or different colors (yellow, white, brown, etc.) within the onycholytic nail plate [Figure 8]. These correspond to the reflections of fungal colonies, invasion, and subungual debris.[29],[30] This is best seen in DLSO
- Ruin pattern: indented areas are seen on the ventral nail (subungual keratosis), and there is distal pulverization characterized by thickening of the nail plate.[31] This pattern is best seen in TDO [Figure 9].
 | Figure 7: Jagged margins at the proximal edge of onycholytic band in onychomycosis (×50)
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 | Figure 8: Onychoscopy shows the presence of multiple striae of different colors (Aurora borealis pattern) in the onycholytic nail plate (×50)
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 | Figure 9: Onychoscopy at the distal end of nail plate showing “Ruin pattern.” Note the friable subungual hyperkeratosis with lifting up of the nail plate (×50)
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There is a lack of comparative studies in this field using other dermatoses as controls. Nevertheless, these features have been corroborated by most of the published work in this field. Correlation with histopathologic evidence is also lacking.
Other reported onychoscopic features of onychomycosis include fungal melanonychia, seen as black-to-brown longitudinal/transverse bands. It can be differentiated from other causes of melanonychia due to its homogenous pigmentation and/or coarse granules or pigmented clumps with the pigmented lines. These granules and clumps correspond to the fungal colonies.[32] It is also reported that the bands here are wider distally and narrow proximally.[32] Dermatophytoma appears as round-shaped yellow-to-orange color patches in the nail plate connected by a narrow channel to the distal nail plate.[30] Recently,” White streaks” has been proposed as a useful dermoscopic sign to differentiate DLSO from nail psoriasis.[33] Other newly described onychoscopic feature is “distal irregular termination” which correspond to distal pulverization characteristic of thickening of nail plate in TDO.[34] Onychoscopy has also been utilized as a tool to locate the best proximal site for mycological sampling.[35]
Nail Psoriasis (Level of Evidence-3) | |  |
Onychoscopic features in psoriasis depend on whether the nail matrix and/or nail bed is involved with psoriasis.[36] Onychoscopy permits a better visualization of features not visible to naked eye. This is in addition to valuable diagnostic information about the disease gleaned from the vascular structures visualized in the PNF and hyponychium.[37] The salient onychoscopic features of nail psoriasis are summarized in [Table 3].
There have been a fair number of studies reporting the frequency of different onychoscopic changes in nails affected by psoriasis. In a study involving 68 patients, Yadav et al.[38] reported nail pitting [Figure 10] to be the most common finding, followed by onycholysis [Figure 11].[38] Psoriatic onycholysis is bordered by a distinct erythema and the edge of onycholysis is relatively straight and not jagged. On the other hand, a recent study of 67 patients reported splinter hemorrhages [Figure 12] to be the most common finding followed by pitting and onycholysis.[39] Onychoscopy also helps identify and delineate salmon patch better than naked eyes.[38],[39] [Figure 13]. | Figure 10: Multiple pits differing in shape and size over the nail plate in psoriasis. Pitting is better appreciated with nonpolarizing onychoscopy (×50)
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 | Figure 11: Distal onycholysis in psoriasis showing the typical erythematous band at the proximal end of onycholytic band (×50)
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 | Figure 12: Onychoscopy of the nail bed showing longitudinal red-to-black-colored streaks indicating splinter hemorrhages (×50)
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 | Figure 13: Multiple orange-to-red-colored area present in nail bed suggestive of salmon patch (×50)
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The presence of onycholysis as a sole feature of nail disease is a fairly common scenario. In such cases, it becomes difficult to diagnose the etiology, if no other cutaneous clues are present. Onychoscopy is a valuable investigation in this scenario as it helps differentiate between the three most common causes of onycholysis [Figure 7] and, [Figure 11] and [Figure 14] as summarized in [Table 4].[45] | Figure 14: Onychoscopy of traumatic onycholysis showing proximal linear edge without striae or erythematous band (×50)
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 | Table 4: Salient onychoscopic features of common causes of distal onycholysis
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Nail Lichen Planus (Level of Evidence-5) | |  |
Not much work has been done on onychoscopy of nail lichen planus. The onychoscopic characteristics have been described in only 3 studies till now,[8],[46],[47] and there have been no attempts to correlate them with clinical features or with histopathology. Even these limited studies have not followed a case–control format, neither have they studied large numbers of nails.
Nail involvement is seen in around 10% of cases of lichen planus.[46] Because of its aggressive behavior, early diagnosis and management becomes necessary. Nakamura et al. described onychoscopic features in 11 patients with 79 affected nails and divided them into nail matrix and nail bed changes.[46] Nail matrix changes included trachyonychia (40.5%) [Figure 15], pitting (34.2%) [Figure 16], pterygium (21.5%) and red lunula (3.8%); while nail bed changes included chromonychia (55.7%) [Figure 17], nail fragmentation (50.6%), splinter hemorrhages (35.4%), onycholysis (27.8%) and subungual keratosis (7.5%). Other features reported included paronychia (31.6%), longitudinal streaks and anonychia. They attempted to identify poor prognostic factors in the form of nail bed features and converging longitudinal streaks which they associated with a poor treatment response. No capillaroscopic changes were observed. Another study by Friedman et al. reported chromonychia, subungual hyperkeratosis, and onycholysis and nail plate destruction as being the onychoscopic features of nail lichen planus.[47] | Figure 15: Trachyonychia in a case nail lichen planus. Fine pitting, onychorrhexis, and onychoschizia can be appreciated (×30)
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 | Figure 16: Pitting in a case of nail lichen planus. Note the extensive nail bed changes seen in the background of nail pits. Nail bed erythema and whitish halos can be appreciated (×50)
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 | Figure 17: Chromonychia in a case of nail lichen planus. Nail bed erythema and yellowish discoloration can be seen (×50)
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Tumors | |  |
Onychoscopy has been used for the evaluation of many tumors. However, the evidence available is only in the form of reports of a single case or a small series. The published reports are summarized below.
Onychomatricoma (Level of Evidence-5)
Onychomatricoma is a benign fibroepithelial tumor specific to the nail apparatus. The classical tetrad includes xanthonychia, ungual hyperkeratosis, splinter hemorrhages, and transverse plus longitudinal overcurvature of nail plate. The onychoscopic features of 34 cases have been described in a study by Lesort et al.[48] They detailed the features in the form of longitudinal parallel white bands (81.8%), parallel lateral edges (96.9%), splinter hemorrhages (81.8%), dark dots (84.8%), nail pitting (93.9%) and thickening of the free edge (93.9%). Dermoscopic features were found to have less inter observer variability as compared to the clinical features.[48]
Onychopapilloma (Level of Evidence-5)
Onychopapilloma is a benign tumor of the nail bed and distal matrix. It presents as longitudinal erythronychia, leukonychia or melanonychia, associated with splinter hemorrhages, and characteristic subungual keratotic mass with distal fissuring. Onychoscopic appearance has been described as a band appearing to originate from the lunula with a proximal convex border and few splinter hemorrhages within.[49] Tosti et al.[50] reviewed 47 cases onychoscopically, reporting red bands originating from the lunula along with splinter hemorrhages. Another characteristic dermoscopic feature of the distal edge is a keratotic subungual mass corresponding to streaks, seen in all the cases [Figure 18] and [Figure 19].[50] | Figure 18: Erythematous band originating from the lunula with splinter hemorrhage seen in onychopapilloma (×50)
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 | Figure 19: Onychoscopy of distal edge of nail in onychopapilloma showing keratotic subungual mass (×50)
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Subungual glomus tumor (Level of Evidence-5)
Glomus tumor is an uncommon benign vascular hamartoma arising from the modified smooth muscle cells of the glomus body. Although histopathology remains the gold standard investigation for confirming the diagnosis, typical onychoscopic features have been described. Onychoscopy of nail plate reveals discrete linear vascular structures. Even more characteristic is the intraoperative appearance (after nail plate removal).[51] It shows the presence of ramified telangiectasiae over blue background at the site of tumor. Tumor margin can be considered corresponding to the abrupt loss of telangiectasiae at the periphery of the mass.[52] Duarte et al. reported an irregular bluish patch with irregular linear vessels on onychoscopy.[53] This can aid in localizing the tumor and delineating the surgical margins.[51] Another study reported the appearance of homogeneous white area of the nail plate and disappearance of the lunula.[54] Onychoschizia was seen involving the distal nail plate.[54] Thatte et al. did UV light dermoscopy of glomus tumor which revealed a “pink glow,” which the authors suggested was because of the vascular nature of the tumor.[55]
Digital myxoid cyst (Level of Evidence-5)
Onychoscopic features of myxoid cyst depend on the pressure applied on the lesion while doing the procedure. When no pressure is applied, vascular patterns in the form of linear, branched, or serpentine vessels are seen. On applying, pressure vascular pattern diminishes, and the lesion shows translucent bright white areas.[56],[57]
Periungual pyogenic granuloma (Level of Evidence-5)
A pyogenic granuloma in the periungual location may present as a diagnostic dilemma. Onychoscopic features described include a reddish homogenous area with white rail lines.[58]
Periungual warts (Level of Evidence-5)
A distinct advantage offered by onychoscopy is in the recognition of warts in early stages of their evolution. This comes particularly handy in the periungual location where other differentials need to be ruled out. Multiple red-black dots corresponding to thrombosed vessels in the keratotic lesions are seen on onychoscopy, helping to differentiate from other tumors arising subungually [Figure 20].[59] | Figure 20: Onychoscopy of periungual wart showing keratotic lesion with multiple red-to-black dots corresponding to thrombosed vessels (×50)
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Periungual Bowen's disease (Level of Evidence-5)
This is again a difficult to diagnose disorder when arising in the periungual location. Onychoscopic features include islands of whitish scale and numerous, diffusely distributed red dotted vessels. The vessels have whitish halo and occur on a whitish-pink background.[60] Nakayama et al. described the presence of these dotted vessels in 1 out of 3 patients with pigmented periungual Bowen's disease.[61] As compared to other body sites, there is a relative absence of glomerular/dotted vessels in the periungual location. This can be explained by the presence of a thick stratum corneum which obscures the visibility of vessels in the papillary dermis. Although Hutchinson's sign is considered a useful marker of periungual melanoma, it has also been reported with periungual Bowen's disease. In this setting, it is known as pseudo-Hutchinson's sign.[62] This was reported in 1 out of 3 patients studied by Nakayama et al.[61] The essential differences are summarized in [Table 5].[62] | Table 5: Hutchinson's sign and Pseudo-Hutchinson's sign in the nail unit
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Digital fibrokeratoma (Level of Evidence-5)
This is another relatively uncommon tumor arising mostly from underneath the PNF. Onychoscopy shows the presence of clumps of homogenous red lacunae divided by a white meshwork-like septal wall. Telangiectasiae can be observed over the adjacent skin.[63]
Leukonychia (Level of Evidence-5) | |  |
Leukonychia can be of diverse origins and multiple patterns. A transverse leukonychia of the toenails commonly results from repeated trauma to the distal nail plate from the shoes while walking. On onychoscopy, it shows one or more white transverse bands in the deep plate with a normal smooth nail plate surface.[59] Bel et al. have reported the presence of longitudinal white streaks with variable thickness, originating from lunula in Hailey–Hailey disease. This is an important early sign of the disease.[64]
Conclusion | |  |
Onychoscopy is a noninvasive and easily reproducible technique which has long been utilized in the study of nail pigmentation and NFC. It has produced consistent results in these conditions and has stood the test of time. Its application, however, in other onychopathies is still in developmental stages. The preliminary results are promising and controlled studies with larger sample size and higher power are needed to build up the evidence. Whether it can replace nail biopsy as a standard diagnostic tool or not, remains to be seen. Nevertheless, onychoscopy has carved out a niche for itself in the current diagnostic scenario.
Financial support and sponsorship
Nil
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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