Dermatologica Sinica

: 2020  |  Volume : 38  |  Issue : 4  |  Page : 205--216

Dermoscopic manifestations of nail diseases

Sushmita Pradhan, Xin Ran, Siliang Xue, Yuping Ran 
 Department of Dermatovenereology, West China Hospital, Sichuan University, Chengdu, China

Correspondence Address:
Prof. Yuping Ran
Department of Dermatovenereology, West China Hospital, Sichuan University, No. 37, Guo Xue Xiang, Wuhou, Chengdu, Sichuan Province 610041


Nail dermoscopy in recent years has become an auxiliary noninvasive tool for the diagnosis of nail diseases. It detects the differentiating characteristics of the nail units and assesses in the management of nail diseases. Dermoscopy may not be a diagnostic tool for all nail diseases; however, it is very useful for early observation with high magnification. This article discusses the important and common dermoscopic manifestations of nail disease cases in the daily practice. Currently, the indications of dermoscopy include viral, bacterial, fungal, inflammatory, pigmented, traumatic nail diseases, nail tumors, and connective tissue disease.

How to cite this article:
Pradhan S, Ran X, Xue S, Ran Y. Dermoscopic manifestations of nail diseases.Dermatol Sin 2020;38:205-216

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Pradhan S, Ran X, Xue S, Ran Y. Dermoscopic manifestations of nail diseases. Dermatol Sin [serial online] 2020 [cited 2022 Dec 8 ];38:205-216
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Dermoscopy of nails is an auxiliary method in the assessment of nail diseases. It is a simple yet very important diagnostic tool for physicians and nail surgeons. Dermoscopy makes the physical examinations of nails easier by helping to diagnose the disease that is insufficient with naked eyes avoiding preliminary misdiagnosis and sometimes biopsy. Different parts of the nail unit invisible to the naked eyes can be magnified and studied to conclude a probable diagnosis to guide the management and prognosis of different nail diseases. Nail dermoscopy is usually evaluated dry in the nail plate surfaces or matrix varying from lower to higher magnification. Dermoscopic observation can be performed using handheld dermatoscope or USB port connected videodermoscope. Nonpolarized dermoscopy allows us to evaluate the nail surface with detailed structural change. Polarized dermoscopy allows us to evaluate the nail unit deeper and avoid the reflectance of light to the nail surface. Ultraviolet (UV) dermoscopy show some special characteristics based on the density of absorbing nature of nail structure change. This article discusses the importance of the common dermoscopic manifestations of nail diseases in daily practice. Dermoscopic manifestations vary according to the characteristics of viral, bacterial, fungal, inflammatory, pigmented, traumatic nail diseases, nail tumors, and connective tissue disease. Even though dermoscopy may not be a diagnostic tool for some nail diseases, it may aid in the rapid abnormality detection of nail diseases.

 Dermoscopic Characteristics of Different Nail Diseases

Viral disease

Hand, foot, and mouth disease

Hand, foot, and mouth disease is a common viral infection caused by Coxsackievirus A16 in children occurring during spring or autumn.[1] It is mainly characterized by vesicular eruptions in the palms, soles, oral cavity, and nail units. Dermoscopy of nail shows painless, noninflammatory condition with proximal shedding of the nail plate from nail matrix [Figure 1].[2] It indicates a sequelae of virus infection several weeks ago where the new nail begins to grow forward and forms a junction line with the separated damaged nail, and careful inquiry of the fever history could get the confirmed diagnosis. Beau lines appear as transverse ridges of the nail plate [Figure 2].[2] Onychomadesis may occur in severe systemic illness, infection, high fever, medications, nutritional deficiency, periungual inflammation, and trauma.[1]{Figure 1}{Figure 2}

Periungual warts

Periungual warts can be seen both in fingernails and toenails. It is mostly caused by human papillomavirus 1, 2, and 4. Differential diagnosis of periungual warts is ungula Bowen disease and squamous cell carcinoma commonly presented with a verrucous lesion confirmed by histopathology.[3] Dermoscopy of periungual warts typically presents hyperkeratotic and rough lesions with micropapules and small black dots corresponding to dilated capillaries of the papillary dermis as cutaneous warts [Figure 3].[4] Dermoscopy may be useful in doubtful cases.{Figure 3}

Fungal disease


Onychomycosis refers to the fungal infection of the nail bed and nail plate mainly caused by dermatophytes (Trichophyton spp., Microsporum spp., and Epidermophyton spp.), nondermatophyte mold and yeasts. Various dermoscopic patterns in onychomycosis are reported. Dermoscopy of distal subungual onychomycosis of the nail plate shows a jagged proximal border of the onycholytic area, with yellow-spikes projecting into the proximal dark yellow background nail plate, as well as the broken comb damage and hyperkeratosis at the far end [Figure 4].[5] Dermoscopy of superficial onychomycosis and proximal subungual onychomycosis of the nail plate shows white opaque friable patches irregularly distributed having KOH-positive [Figure 5].[6] Dermoscopy of subungual hyperkeratosis in the distal-free edges shows ruined appearance and collection of scales corresponding to fungal presence [Figure 6].[7] Yorulmaz and Yalcin reported the most common dermoscopic manifestations in 81 patients with onychomycosis was jagged-spike pattern of onycholysis in 52% followed by subungual ruin pattern and whitish patches (leukonychia).[8] In our experience, dermoscopy is diagnostics for onychomycosis.{Figure 4}{Figure 5}{Figure 6}

Bacterial infection

Paronychia is an inflammatory disease affecting the proximal and lateral nail folds mainly occurring as acute and chronic paronychia.

Acute paronychia

Acute paronychia is a nail infection due to bacterial penetration of the cuticle or the nail fold from direct or indirect trauma with inoculation of pathogens, mainly Staphylococcus aureus and ß-hemolytic Streptococcus.[9] It is presented with swelling, erythema, tenderness, throbbing, and pus formation.[10] Dermoscopy of acute paronychia shows erythematous pus discharge from proximal or lateral nail folds or uplifting of nail plate due to infection of the nail bed [Figure 7].[11]{Figure 7}

Chronic paronychia

Chronic paronychia refers to the swelling of the proximal nail fold and the disappearance of the cuticle mainly caused by finger sucking in children.[12] Dermoscopy shows painful acute inflammation due to secondary colonization with Candida albicans and/or bacteria [Figure 8]. Chronic paronychia in proximal nail fold is caused by the irritative reaction, contact allergy, food hypersensitivity, Candida hypersensitivity, and true Candida paronychia.[11]{Figure 8}

Inflammatory disease

Nail psoriasis

Nail psoriasis usually affects nail plate, nail bed, hyponychium, and nail matrix. Nail psoriasis is characterized by pitting, nail discoloration (salmon patch and oil drop), onycholysis, subungual hyperkeratosis, and splinter hemorrhage.[13] Pitting, crumbling, and leukonychia are involved in nail matrix; red spots in lunula; and onycholysis, oil spots, subungual hyperkeratosis and splinter hemorrhages are involved in nail bed.[14] Pitting are small punctuate depressions of the nail plate surface that results from defective keratinization of the foci of the cells of the proximal nail matrix commonly seen in psoriasis and alopecia areata.[4] Dermoscopy shows pitting as large, deep, and irregular in size, and distribution covered by large scales [Figure 9].[4] UV dermoscopy of pits shows light-green fluorescence [Figure 10]. Onycholysis in psoriatic fingernails is characterized by an erythematous border surrounding the distal edge of the detachment, by signs of nail bed inflammation, on dermoscopy shows bright yellow/white, slightly dented margin of the detachment [Figure 11].[4] Leukonychia of psoriatic nails is due to internal desquamation of keratinocytes that is unable to flake off because of the parakeratosis of the distal nail matrix.[15] Dermoscopy of leukonychia shows single or multiple opaque white irregular spots on the nail plate surface [Figure 12].[4] Nail discoloration, namely “oil drop” or “salmon patch” is characterized by a reddish yellow color on the nail bed like a drop of oil under the nail plate which is caused by parakeratosis and tightly arranged acanthosis under the nail plate.[13],[16] Dermoscopy of oil drop or salmon patch shows a circular translucent yellow-red area of discoloration in the middle of the nail of surrounding onycholysis [Figure 13].[4] Splinter hemorrhage can be seen as a small line with 3 mm length in the distal nail plate.[16] Dermoscopy of splinter hemorrhage shows the longitudinal orientation of the red lines allowing the observation of nail bed capillary dilations that precede rupture [Figure 14].[4] Subungual hyperkeratosis is characterized by the accumulation of scales under the nail plate, which is detached and uplifted due to excessive proliferation of nail bed/hyponychium keratinocytes.[4] Diffuse subungual hyperkeratosis is seen in psoriasis and distal subungual onychomycosis.[4] Dermoscopy of subungual hyperkeratosis in psoriasis shows accumulation of scales under the nail plate [Figure 15]. In a recent study done by Sari et al. showed pitting (58.8%), onycholysis (46.6%), Beau's line (46.6%), splinter hemorrhage (46.6%), salmon patch (33.3%), and subungual hyperkeratosis (33.3%) as the common dermoscopic findings in nail psoriasis.[17] They also found that dermoscopy cannot be replaced to histopathological examination as a diagnostic tool to nail psoriasis.[17] Yorulmaz and Artuz described “pseudo-fiber sign” as a new dermoscopic feature of nail psoriasis resembling red and black filamentous structures located along the cuticle, underneath the distal free edge on the hyponychium of nail plate detached areas suggested that it was related to nail bed psoriasis with bare capillaries.[18]{Figure 9}{Figure 10}{Figure 11}{Figure 12}{Figure 13}{Figure 14}{Figure 15}

Nail lichen planus

Nail lichen planus is seen in 10% of the cases with lichen planus affecting fingernails than toenails.[19] The most common signs of nail lichen planus affecting nail plate are thinning, splitting, fissuring, longitudinal ridging, grooving, and atrophy. Dorsal pterygium is due to the irreversible damage to part of the nail matrix allowing adhesion of dorsum skin of the digit to the nail bed, forming a V-shaped extension of the proximal nail fold splitting the nail plate into two parts.[4] Dermoscopy shows formation from skin continuing with the skin of the proximal nail fold [Figure 16].[4] The color is pink red with elongated capillaries in early lesions.[4] Trachyonychia or “20-nail dystrophy” is characterized by a benign disease with rough nails-like sandpaper in a longitudinal direction. It can also be caused by psoriasis, lichen planus, or alopecia areata. Dermoscopy of the nail plate shows multiple fine and superficial longitudinal fissures covered by thin scales [Figure 17].[4] Longitudinal fissuring and distal splitting are the typical signs of nail matrix lichen planus where the nails are thinned showing longitudinal ridging and fissuring with distal splitting.[4] Dermoscopy shows multiple deep longitudinal fissures reaching the distal part of the nail as well as partial absence of the nail plate.[4] Dermoscopy is a useful diagnostic tool for therapeutic evaluation of the proximal nail plate to observe the emerging nail fold showing the regrowing of the nail plate in nail lichen planus.[4] In a study of dermoscopy of nail lichen planus done by Nakamura et al. showed abnormalities of the nail matrix with trachyonychia (40.51%), pitting (34.18%); anomalies of nail bed with chromonychia (55.7%), fragmentation of nail body (50.63%), splinter hemorrhage (35.44%), onycholysis (27.85%), subungual keratosis (7.59%); anomalies of nail matrix, bed and perionychial region with longitudinal streaks (82.28%), anonychia (1.27%); and paronychia (31.65%).[20]{Figure 16}{Figure 17}

Nail pigmentation

Longitudinal melanonychia

Longitudinal melanonychia refers to the black-brown pigmentation of the nail due to the presence of melanin within the nail plate.[4] Longitudinal band starting from the proximal margin that extends to the distal margin involving the whole nail plate is called total melanonychia.[4] Longitudinal melanoma is present in 70% of the cases.[21] Nail melanoma is rare in Caucasian (1%–2% of melanomas), however, common in Asians (10%–20%) and Africans (25%).[21] Three important steps in evaluating melanonychia are to establish the pigment is melanin or not; to determine the development of melanonychia is due to activation or proliferation of matrix melanocytes, and; to assess if there is a proliferation to determine the disease is benign or malignant.[22] The ABCDEF rule for nail pigmentation[23] should be applied while using dermoscopy.[24] Dermoscopy of longitudinal melanonychia in children with low specificity suggest melanoma includes a brown background involving most of the nail plate with longitudinal brown to black lines with an irregular color, spacing, thickness, and abrupt ending [Figure 18].[25] Dermoscopy pattern for nevus shows brown background with longitudinal brown-black regular and parallel lines with regular spacing and thickness, whereas in children black dot due to pigment accumulation occurs in the nail plate.[4] Benati et al. identified three important dermoscopic pattern in nail band pigmentation that helped to distinguish a band from benign to malignant: width of the band, involving more than two-thirds of the nail plate in melanoma; presence of a gray-to-black color; and presence of nail dystrophy that increased the risk of nail melanoma detection three times more.[26] There lies high probability of diagnosis of nail melanoma in the presence of micro-Hutchinson sign indicating early or in situ lesions.[4] Micro-Hutchinson sign could be associated with a band of melanonychia or with amelanotic melanoma, characterized by the lack of melanin pigment [Figure 19].[4] Dermoscopy of nail melanoma suggest a brown-to-black background of the band with longitudinal lines irregular in their thickness, spacing, color, or parallelism where sometimes ABCDEF rule may not be applied with findings of irregular width or color observed in benign lesions [Figure 20].[27] Hirata et al. identified four intraoperative dermoscopic patterns: regular gray pattern typical for hypermelanosis, regular brown pattern typical for benign melanocytic hyperplasia, regular brown pattern with globules or blotches typical for melanocytic nevi, and an irregular pattern, typical for melanoma assisted in selecting best site for performing biopsy.[28] Although ABCDEF rule is applied in the dermoscopy of longitudinal melanonychia, histopathology is still a definitive method for nail pigmentation.[29]{Figure 18}{Figure 19}{Figure 20}

Green nail

Green nail is characterized by a green or black discoloration due to colonization by Pseudomonas aeruginosa producing a pigment named pyocyanin adhering to the irregular nail plate surface or located under an onycholytic nail plate.[30] Dermoscopy shows yellow-green discoloration and its localization [Figure 21]. Differential diagnosis consists of paronychia, onycholysis, and chemical exposures to solutions such as pyocyanin or pyoverdine.[31]{Figure 21}

Subungual hematoma

Subungual hematoma or subungual hemorrhages are a collection of blood in the space between the nail bed or matrix and the nail plate resulting from an acute painful injury or repetitive minor trauma to the nail apparatus.[32] Subungual melanoma or longitudinal melanonychia should be kept in the differential diagnosis as it can easily be misdiagnosed.[33] An acute subungual hematoma is easy to diagnose which explains the history of trauma. However, the chronic subungual hematoma is caused by repeated microtraumas where brown-black pigmentation of a toenail should be differentiated from melanotic pigmentation, i.e., from nail melanoma.[4] Dermoscopy shows the round shape of hematoma and its homogenous pigmentation [Figure 22]. The studies show that subungual hemorrhages exhibit a variety of colors upon dermoscopic examination. Ronger et al. first described the dermoscopic pattern of 22 cases of subungual hemorrhages by following terms: rounded proximal edge, purple-blue to brown color, and distal edges with a somewhat liner distortion.[24] Recently, Mun et al. studied 90 cases of subungual hemorrhages demonstrated the structures of blood spots in homogeneous pattern (n = 83, 92%), globular pattern (n = 38, 42%) and streaks (n = 35, 39%); peripheral fading (n = 49, 54%), periungual hemorrhages (n = 20, 22%) and destruction or dystrophy of the nail plate (n = 14, 16%).[34] They also exhibited a combination of more than one color in 84% of cases and only one color in 16% of cases.[34]{Figure 22}

Traumatic nail abnormalities

Traumatic onycholysis

Traumatic onycholysis is one of the most common toenail abnormalities consisting of bilateral and symmetrical. Dermoscopy of traumatic onycholysis shows a line of a detachment of the plate from the bed appearing linear, regular, and smooth surrounded by a normally pale pink bed without hyperkeratosis [Figure 23].[35] Meanwhile, secondary fungal infection as onychomycosis with brown to yellow-spikes might occur. Subungual space is usually whitish to yellow.[4]{Figure 23}

Traumatic or frictional melanonychia

Traumatic or frictional melanonychia occurs in the fingernails of individuals who bite or traumatize the proximal nail fold and cuticle.[36] It may also appear in the fourth and fifth toenails which are exposed to chronic friction from the shoes. Dermoscopy of traumatic melanonychia shows a homogeneous gray pale brown or gray band [Figure 24].{Figure 24}


Onychotillomania is a nail-picking disorder that is characterized clinically by general dystrophy and abnormal morphology of the nail plate, as well as damage to the nail bed and periungual skin.[23] Onychotillomania is commonly misdiagnosed and often confused with and treated as other nail disorders such as lichen planus, psoriasis, or onychomycosis.[37] Dermoscopy shows linear nail bed hemorrhages, periungual crusts, scales, hemorrhages, and wavy lines [Figure 25].[23] Maddy et al. evaluated dermoscopic features of 36 onychotillomania cases showed scales (n = 34, 94.4%), absence of nail plate (n = 30, 83.3%), wavy line (n = 25, 69.4%), hemorrhages (n = 23, 63.9%), crust (n = 22, 61.1.%), nail bed pigmentation (n = 17, 47.2%), speckled dots (n = 14, 38.9%), and nail plate melanonychia (n = 4, 11.1%).[23] They concluded that the absence of nail plate with multiple obliquely oriented nail bed hemorrhages, nail bed gray pigmentation, and presence of wavy lines were characteristic features of onychotillomania not observed in other nail diseases.[23]{Figure 25}

Nail tumors

Bowen disease

Bowen disease may affect periungual skin gradually destroying the nail plate. Dermoscopy of Bowen disease reveals dotted and/or glomerular vessels, islands of whitish scales, and hyperkeratotic, targetoid structures [Figure 26].[38] Dermoscopy of subungual Bowen disease also showed an inhomogeneous, blocky pigment streak fading toward the distal side.[39] Dermoscopy of woodgrain appearance of nail plate due to transepidermal elimination of tumor cell nests was also reported.[40] Brownish dots along the imaginary lines in pigmented Bowen disease has also been reported.[41] Longitudinal melanonychia may only be seen in some cases of Bowen disease.{Figure 26}


Onychopapilloma is a benign tumor arising from the distal matrix or proximal nail bed, including a band of longitudinal erythronychia, longitudinal leukonychia, longitudinal melanonychia or just splinter hemorrhages, with or without distal fissuring.[42] Dermoscopy shows a longitudinal red band, starting from the lunula and reaching to the distal margin, often associated with splinter hemorrhages [Figure 27].[4] Tosti et al. performed a dermoscopic study of 47 patients with onychopapilloma observed distal edge showing a keratotic subungual mass in correspondence to the streak and splinter hemorrhages as the only dermoscopic sign.[42] Onychopapilloma often shows a subungual filiform mass from the distal margin, whereas onychomatricoma shows characteristic features of multiple holes.[4] Dermoscopy of onychomatricoma shows honeycomb aspect of the distal part of the nail plate which is a diagnostic feature.[4]{Figure 27}

Glomus tumor

Glomus tumor is a painful benign nail tumor mostly occurring in the subungual area of the hand (first and second fingernails) presenting approximately 1%–2% of all hand tumors.[43],[44] The classic triad of symptoms include intense paroxysmal pain, pinpoint tenderness, and cold sensitivity.[45] Dermoscopy of glomus tumor appears as an oval deep red-purple discolored area with blurred borders or a band of longitudinal erythronychia that does not usually reach the distal margin [Figure 28].[46] Intraoperative dermoscopy of the nail matrix and bed after nail plate removal before tumor excision aids in tumor localization and in visualization of the vascular pattern of the lesion appearing as ramified telangiectasis over a blue background suggesting the diagnosis of glomus tumor.[47]{Figure 28}

Pyogenic granuloma

Pyogenic granuloma is a benign vascular tumor that occurs in the periungual tissues, and nail bed mainly due to trauma, in growing nails, drugs appearing as a bleeding vascular nodule, peripheral nerve injury, and inflammatory disease.[48] Dermoscopy of pyogenic granuloma shows a vascular pattern with red color and milky-red veil and a regular pattern of the vessels [Figure 29].[4] The center of the lesion is red and darker, whereas the periphery is paler.[4] Brown color is seen with necrotic lesions.[4] Dermoscopy may not be diagnostic for pyogenic granuloma in cases of masses present on the nail bed which can be differentiated from squamous cell carcinoma and melanoma only through histopathological examination.[4] However, dermoscopy can be used to detect the masses on the lateral and proximal nail folds.[4]{Figure 29}

Connective tissue disease

Structural capillary abnormalities can be documented in periungual connective tissue diseases such as systemic sclerosis, dermatomyositis, mixed connective tissue disorder, Raynaud's phenomenon, and other systemic diseases.[49] Based on the severity of the connective tissue disease capillary abnormalities they can be classified as early changes (enlarged capillaries and hemorrhage), active disease (frequently enlarged capillaries and frequent hemorrhage), and late changes (irregular enlargement and severe loss of capillaries and avascular areas).[49] Dermoscopy of systemic lupus erythematous shows early nail fold hemorrhagic capillaries [Figure 30]. Dermoscopy of dermatomyositis shows active structural dilated capillary abnormalities also known as “scleroderma pattern” similar to systemic sclerosis [Figure 31].[49]{Figure 30}{Figure 31}


This review demonstrates the importance of nail units' dermoscopy affecting the subungual regions rapidly assisting in the diagnosis of various nail diseases in daily practices. Distinctive dermoscopic signs of various nail diseases have also been described and allowed a differential diagnosis [Table 1]. Its importance must be taken into consideration in cases of doubtful diagnosis before histopathological examinations. Further studies may help clarify the importance of recent advances of dermoscopy in nail diseases. Nevertheless, it is important for general practitioners and dermatologists to be able to diagnose nail diseases using dermoscopy.{Table 1}

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