Clinical Dermatology Review

SYMPOSIUM: BASICS OF DERMOSCOPY AND DERMOSCOPIC PATTERNS
Year
: 2020  |  Volume : 4  |  Issue : 2  |  Page : 92--101

Nail disorders in skin of color: Approach to onychoscopic diagnosis


Balachandra S Ankad1, Yasmeen Jabeen Bhat2, Sakshi S Gaikwad1,  
1 Department of Dermatology, S. Nijalingappa Medical College, Bagalkot, Karnataka, India
2 Department of Dermatology, STD and Leprosy, GMC, Srinagar, Jammu Kashmir, India

Correspondence Address:
Balachandra S Ankad
Department of Dermatology, S. Nijalingappa Medical College, Navanagar, Bagalkot - 587 102, Karnataka
India

Abstract

Onychoscopy provides a better understanding of nail lesions in terms of diagnosis, monitoring of progression and response to treatment. Author have put forward a simplified way to approach to a nail lesion by onychoscopy. Onychoscopy of pigmentary, inflammatory, infections, neoplastic and connective tissue diseases affecting the individual of skin of color are described to construct a basic outline for onychoscopic approach to a nail lesion. Onychoscopy shows homogenous dark band in longitudinal melanocytic nevus (LMN), irregular black pigment with irregular longitudinal lines in melanoma, multi-colored pigmented patches in fungal melanonychia, purplish-black in subungual hematoma, transverse bands in the under surface of plate in true leukonychia, whitish- yellow patches in pseudoleukonychia. In psoriasis, irregular pits, salmon spots are seen whereas in lichen planus onychorrhexis, whitish linear splits and pterygium are observed. Eczema shows pits with lusterless surface. In Darier's disease, characteristic alternate white and red bands are present. Lichen striatus shows longitudinal erythematous bands and ridging. Red dots with white halos are characteristics in warts. Onychomycosis shows 'aurora borealis' pattern and white opaque and friable spots. Bowen's disease shows white scales with red dots. 'Woodworm appearance' and keratotic mass are seen in onychomatricoma and respectively. Squamous cell carcinoma reveals destruction of nail plate and glomus tumor demonstrates pinkish blush. In connective tissue diseases, characteristic changes are present nail fold capillaries. Onychoscopy assists in the analysis and differentiation of many dermatoses which affect nail unit with similar clinical manifestations.



How to cite this article:
Ankad BS, Bhat YJ, Gaikwad SS. Nail disorders in skin of color: Approach to onychoscopic diagnosis.Clin Dermatol Rev 2020;4:92-101


How to cite this URL:
Ankad BS, Bhat YJ, Gaikwad SS. Nail disorders in skin of color: Approach to onychoscopic diagnosis. Clin Dermatol Rev [serial online] 2020 [cited 2020 Sep 19 ];4:92-101
Available from: http://www.cdriadvlkn.org/text.asp?2020/4/2/92/292484


Full Text



 Introduction



Nail dermoscopy (onychoscopy) refers to the examination of the nail unit using a dermoscope, requiring a good knowledge of nail anatomy and physiology and the pathogenesis of nail diseases. It can be performed with a hand-held dermoscope or a videodermoscope, which allows higher magnifications. Initially used in the study of nail pigmentations only, onychoscopy has gradually become more and more frequently utilized to observe other types of neoplastic and nonneoplastic nail disorders.[1]

Onychoscopy is a noninvasive and rapid office-based technique suited for a better understanding of nail pathologies, allows photographic documentation and monitoring of progression and response to treatment.[2] The indications of onychoscopy are many, including pigmentary onychopathies, infections, inflammatory diseases, trauma, nail tumors, and connective tissue disorders.

As in dermoscopy of the skin, both contact and noncontact dermatoscopes can be used for onychoscopy. In onychoscopy, both nonpolarized and polarized light sources are essential. Nonpolarized light source is used for studying the surface anatomy as well as the associated nail changes, whereas polarized light is suited for the study of nail pigmentation and its vascularity. The usual protocol is to start with lower magnification (×10) for a general overview of nail pathology and then move to the higher magnification (×50–×200) for eliciting finer details. Nail plate should be thoroughly cleaned with acetone/spirit to remove debris, dirt, or external applications. The initial examination is a “dry examination” (without any interface medium), though later, a “wet examination” (using an interface medium) is needed. Whereas nail plate changes or surface irregularities are seen well with the dry examination, nail bed changes are better visualized by wet examination, since the interface medium increases the transparency of plate and penetration of light.[3] The use of an interface medium like immersion oil, ultrasound gel, and antiseptic alcohol solution leads to better visualization of color changes and vascularity.[4] Ultrasound gel is considered to be superior to alcohol for the examination of the nail apparatus because the viscosity of the gel prevents it from rolling off the convex nail surface. Ultrasound gel is also necessary for the examination of periungual folds and hyponychium.[3]

 Approach to a Nail Lesion



Onychoscopy of any given nail lesions should be carried out in a methodological protocol that consists of the following steps. Onychoscopic approach to nail lesions includes examination of (i) nail plate, (ii) nail bed (iii) proximal nail fold (iv) hyponychium and (v) distal free edge of the nail plate and they address all the clinical manifestations of a disease condition affecting the nail unit.[4] Onychoscopic appearance of the normal nail plate, proximal fold, hyponychium, and distal free edge is depicted in [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d, respectively. Normal capillary loop in the proximal fold with higher magnification (with difficulty in ×10 magnification) appear as uniform multiple looped vessels in regularity in terms of size, shape, and distribution [Figure 1]e.{Figure 1}

Pigmentary, inflammatory, infective, tumorous, and connective tissue diseases (CTDs) affecting the nail unit are dealt with and analyzed by onychoscopy. Here, authors have attempted to simplify the approach by describing a few common nail disorders in skin of color.

 Onychoscopic Approach to Pigmentary/chromonychia Onychopathies



Pigmentation of the nail unit varies between black, brown, purple, white or greenish. Many etiologies are attributed to these pigmentary changes. Subungual hematoma, melanocytic nevus, and melanoma manifest with band or irregular pigmentation on the nail plate in which color varies from light brown to purplish to darker black.

Onychoscopy of subungual hematoma shows purple or bluish-black colored areas with round proximal margins and filamentous and streaked margins at the distal end in recent injury [Figure 2]c. In older trauma [Figure 2]d, yellowish-brown colored areas with multiple small pale red globules or splinter globules are noted.[2] In both situations, surface appears as glazed or ground-glass pattern. Thus, in subungual hematoma, nail plate shows whitish glazed areas, nail bed shows purplish-black or reddish-brown globules or structures with streaks and filaments without any onychoscopic changes in the proximal fold, hyponychium and free edge of the nail plate.{Figure 2}

Longitudinal melanocytic nevus (LMN) appears as a uniform dark band which is homogenous in color and width and sometimes, dark band may appear on the paler background. Pseudo-Hutchinson's sign [Figure 2]a, the pigment band below the transparent proximal nail fold is characteristic of the nevus. Evaluation of the distal free edge of nail plate reveals the origin of nevus in the nail matrix. Dorsal [Figure 2]b and ventral pigmentation on free edge indicate nevus cells are from proximal and distal matrix, respectively. Thus, in the systematic approach toward LMN, nail plate reveals uniform band of brown or black color, proximal nail fold shows pseudo-Hutchinson's sign and free edge shows ventral or dorsal pigmentation without any onychoscopic patterns in hyponychium.[5]

Melanoma, on the contrary, demonstrates a darker black pigment band with blurred lateral margins, longitudinal lines of different colors with variation in the thickness. Hutchinson's sign, pigmentation in the cuticle or periungual areas, is highly specific for nail melanoma. Pigmentation extends even to hyponychium.[6] Hence, in melanoma, irregular pigment band without parallelism on the nail plate, Hutchinson's sign in proximal nail fold, or irregular pigmentation in the hyponychium and full-thickness pigmentation in the distal free edge are seen.

Fungal melanonychia (FM), which presents with melanonychia shows multicolored pigmented clumps, striations, globules and patches with a blackish-brown reverse triangle, with the base at the distal edge and pointing proximally compared to that of melanoma.[7]

Leukonychia, the whitish discoloration of the nail plate, is mainly due to the involvement of the distal nail matrix (true leukonychia), nail bed (apparent leukonychia) or from an external source (pseudoleukonychia) especially because of onychomycosis. Onychoscopy of true leukonychia shows white dots and clods [Figure 2]e or transverse bands in the deep plate, with a normally smooth nail plate surface whereas in pseudoleukonychia whitish-yellow opaque clods are noted due to superficial desquamation of the nail plate [Figure 2]f.[6] Hence, in pseudoleukonychia due to onychomycosis, whitish-yellow patches are seen on nail plate and whitish clods in hyponychium. Free edge appears whitish with ragged margins in onychoscopy.

Erythronychia, the reddish longitudinal discoloration of the nail plate, can be seen in onychopapilloma, Darier's disease, etc., Onychoscopy of the free edge of the nail plate shows a small subungual keratotic mass in the former and a V-shaped nick in the latter.

Onychoscopic approach to a nail lesion with chromonychia is shown in [Table 1].{Table 1}

 Onychoscopic Approach to Inflammatory Onychopathies



Psoriasis and lichen planus are the most common inflammatory diseases that affect the nail unit followed by eczema and Darier's disease.

The involvement of nail matrix in nail psoriasis shows pitting, trachyonychia [Figure 3]a, Beau's lines, leuconychia and mottled lunula in the nail plate. Under onychoscopy, pits appear as irregular depressions surrounded by white halo [Figure 3]b on the nail plate and Beau's lines are noted as transverse depressed lines across the nail plate.[6]{Figure 3}

Nail bed changes in psoriasis are onycholysis, splinter hemorrahges, salmon spots and subungual hyperkeratosis. Onycholysis is separation of nail plate from the bed in which onychoscopy shows erythematous band at proximal portion of onycholytic area [Figure 3]b. This erythematous band is highly specific to nail psoriasis as it is not seen in other causes of onycholysis.[8]

Splinter hemorrhages are the linear purplish or dark reddish streaks [Figure 3]a whereas salmon spots are reddish-orange areas that vary in size and shape.[9] It should be noted that salmon spots appear as dull red in skin Types IV and V [Figure 3]c as compared to skin types I, II and III wherein it looks reddish-orange. Subungual hyperkeratosis in the accumulation of excessive scales below the nail plate lifting the plate.[10] It appears as yellowish-white structureless area [Figure 3]d. Proximal fold shows alterations in capillary architecture with coiled and drop out vessels. Hyponychium shows typical dotted vessels in homogeneous pattern with a pinkish background [Figure 3]e. Lastly, the free edge of the nail plate shows a thickened nail plate.[11]

Nail lichen planus shows numerous changes in onychoscopy, and most of the changes are destructive in nature, producing deformities of nail unit as compared to other inflammatory diseases. Nail matrix involvement results in onychorrhexis and longitudinal ridges, which appear as transverse splits [Figure 4]a and whitish linear splits [Figure 4]b in the nail plate, respectively. Pterygium appears as reddish-brown area that is extending on the nail plate longitudinally towards the free edge [Figure 4]c. White keratotic structures are seen at the distal end of pterygium. Loss of lunula [Figure 4]b is another definitive onychoscopic pattern in nail lichen planus.[12]{Figure 4}

Chromonychia [Figure 4]d and fragmented dorsum nail plate [Figure 4]b constitute other onychoscopic patterns.

Nail bed changes in lichen planus may appear similar to nail psoriasis, which consists of onycholysis, splinter hemorrhages [Figure 4]a, and subungual hyperkeratosis.[12] Proximal nail fold in lichen planus is not involved commonly except for pterygium, wherein it is destroyed completely due to fibrosis. Few cases may show paronychia affecting the proximal fold. Hyponychium probably shows white fibrotic streaks that end in the free edge and converge at the center of nail plate [Figure 4]e. Distal free edge shows onychoschizia, the splitting of nail plate, due to the brittleness of nail unit.[3],[12]

Eczema of hands and feet occasionally affects respective nail units. Onychoscopic changes in eczema are mainly extrinsic. According to the methodological approach to the diagnosis, nail plate shows lusterless surface, tiny pits, and white scales [Figure 4]f. Although nail bed, proximal nail fold, hyponychium and free edge of nail plate do not demonstrate definitive onychoscopic patterns in eczema, they demonstrate nonspecific pigmentary and vascular changes in chronic and extensive eczematous lesions.[13]

Darier's disease shows red or white longitudinal bands often ending in a pathognomonic notch at the free margin of the nail.[14] Hence in the stepwise approach of onychoscopy, nail plate shows alternate white and red bands with white scales. Nail bed, proximal nail fold and hyponychium do not show any patterns. Free edge of nail plate reveals irregularly broken and V-shaped nick.

Lichen striatus of nail unit presents as longitudinal ridging at the paramedian position of nail plate. Onychoscopy demonstrates, based on approach, longitudinal erythematous bands disrupting lunula, longitudinal ridging, and onychorrhexis in the nail plate, whereas nail bed reveals reddish background. Proximal nail fold and hyponychium do not reveal any patterns. Distal free edge shows the splitting of nail plate.[15] Onychoscopic approach to an inflammatory lesion affecting the nail unit is depicted in [Table 2].{Table 2}

 Onychoscopic Approach to Infective Onychopathies



Common infective conditions that affect nail unit in daily practice include onychomycosis, viral warts, and chronic paronychia. Onychomycosis involves matrix, bed, and plate. Although mycological tests are the definite diagnostic methods, onychoscopy shows few exclusive patterns such as jagged edges of onycholytic area, spikes, and longitudinal striae of different colors simulating aurora borealis.[16]

Nail plate, based on the onychoscopic approach, in (i) distal and lateral subungual onychomycosis (DLSO) nail plate, shows spikes at the proximal portion of onycholytic area. Spikes represent the white longitudinal indentations [Figure 5]a that point toward the proximal end of nail unit and are suggestive of proximal progression of fungus. Longitudinal striae with irregular pigmentation of different color which varies from white, yellow and brown are also affirmative of onychomycosis termed as “aurora borealis” pattern [Figure 5]b; in (ii) total dystrophic onychomycosis (TDO) reveals complete destruction of nail plate with crumbling and thickening of nail plate with indentations on the ventral portion of the nail plate and downward colonization at the subungual level, referred to as “ruin appearance” [Figure 5]c; in (iii) superficial white onychomycosis shows white opaque and friable spots with slight scaling on the nail plate [Figure 5]d; in (iv) FM shows multicolored pigmented streaks, areas and patches at the distal edge of nail plate; and in (v) endonyx type showing the dendritic pattern of striae on nail plate.[17],[18]{Figure 5}

Nail bed demonstrates onycholysis without a reddish band at the proximal portion, subungual hyperkeratosis as yellowish-white structures [Figure 5]e below the nail plate and splinter hemorrhages as linear dark red or purplish streaks [Figure 5]d.[6] Proximal nail fold is commonly affected in proximal and lateral subungual onychomycosis (PSO), and onychoscopy shows rugged cuticle with whitish-yellow areas in lunula.[19] Hyponychium in onychomycosis may show scaling and erythema. Free edge in DLSO and TDO shows thickening of nail plate and is termed as “distal irregular termination.”[19]

Viral warts or verruca vulgaris (VV) is caused by human papilloma virus and clinically presents as verrucous papules and plaques. Onychoscopy of VV shows characteristic red dots with white halos. Nail plate is usually not affected; however, there can be onycholysis due to subungual lesions. Nail bed, proximal nail fold [Figure 5]f and hyponychium with VV lesions show identical onychoscopic patterns as mentioned above. Free edge does not show any patterns.[20]

Chronic paronychia is a chronic inflammation of proximal nail fold usually seen in the fingers. According to onychoscopic approach, nail plate shows longitudinal grooves and proximal nail fold reveals boggy, red-colored swelling with absence of cuticle. Nail bed shows the separation of nail plate from the bed. Hyponychium and free edge do not show onychoscopic patterns.[6] Onychoscopic approach to an infective nail lesion is presented in [Table 3].{Table 3}

 Onychoscopic Approach to Nail Tumors



Tumors that affect nail unit commonly include onychopapilloma, onychomatricoma, Bowen's disease, SCC, and subungual malignant melanoma. Onychoscopic approach in each tumor is described.

Onychopapilloma is a benign tumor of the nail bed and distal matrix and presents as distinctive longitudinal erythronychia.[21] Nail plate shows longitudinal reddish or pinkish linear structure running from lunula to the free edge of nail. Proximal nail fold and hyponychium are unaffected. Nail bed reveals splinter hemorrhages as few short or long dark reddish lines, and free edge of nail plate demonstrates keratotic mass.[21]

Onychomatricoma is a fibroepithelial tumor of benign nature that arises from nail matrix and grows within the nail plate. In accordance with onychoscopic approach, nail plate shows sharply demarcated whitish or yellowish parallel and longitudinal lines. Nail bed reveals hairpin vessels, splinter hemorrhages, and distinctive polychromatic area. Proximal nail fold and hyponychium are unaffected. Free edge is convex and thickened with characteristic honeycomb-like cavities and this pattern is referred to as woodworm appearance.[13],[21]

Bowen's disease presents as scaly erythematous patch with well demarcation with a variable amount of melanin. The prime location of tumor is the periungual skin of the finger. Onychoscopy demonstrates typical clusters of white scales red dotted vessels. In a pigmented variant, brown dots are expected. Since periungual tissue is affected, onychoscopic changes are noted in the proximal nail fold and hyponychium with features mentioned above.[6],[22]

Squamous cell carcinoma of nail presents with onycholysis, oozing and partial loss of nail unit or sometime hyperkeratotic and verrucous growth in the periungual area is seen. In onychoscopic approach, nail plate deformity is noted due to destruction and onycholysis, and accumulation of keratin material with atypical and hairpin-like vessels are observed in the nail bed. Proximal nail fold and hyponychium do not reveal any onychoscopic patterns as they are destroyed.[23]

Lastly, glomus tumor affecting the nail unit shows pinkish blush [Figure 6]a in the nail plate in onychoscopy. If tumor is present near the lunula, there is the disruption of lunula or loss of lunula. Ultraviolet light dermoscopy shows a “pink glow;” suggestive of the vascular nature of the tumor.[24] Onychoscopic approach to a nail tumor is shown in [Table 4].{Figure 6}{Table 4}

 Onychoscopic Approach to Connective Tissue Disease



A dermoscope can aid to detect nail fold changes in CTDs that may have an association between the degree of nail fold capillary abnormalities and internal organ involvement and mortality.[25] Higher magnification is necessary to visualize capillary morphological alterations, which are important for disease scoring purposes because 10x cannot serve the purpose for early dilation, bending or kinking of vessels, criss-cross vessels, bushy vessels, tortuosity, etc. Lower magnification ×10 serves the purpose for noting changes like hemorrhage, giant capillaries, avascular areas, etc.

According to onychoscopic approach, in systemicsclerosis three stages can be classified based on the morphology. Early changes (few enlarged capillaries and few hemorrhages); active disease (frequently enlarged capillaries and frequent hemorrhages); and late changes (branching vessels and disorganized architecture, severe loss of capillaries and avascular areas) [Figure 6]b.[26]

In dermatomyositis, on the basis of onychoscopic parameter; nail plate shows red lunula, nail bed shows splinter hemorrhages, and proximal nail fold demonstrates cuticular changes with capillary loops in the form of ramified capillaries, capillary loss and twisted capillaries and hemorrhages [Figure 6]c.

Patients with systemic Lupus erythematosus show longitudinal ridging, red lunula and bluish-black discoloration of the nail plate, onycholysis, splinter hemorrhages, and subungual hyperkeratosis in the nail bed. Proximal nail fold reveals tortuous capillaries with a characteristic meandering of capillaries.[25],[26] Onychoscopic approach to a nail lesion in CTDs is given in [Table 5].{Table 5}

 Onychoscopic Approach to Traumatic Onychopathies



Traumatic onychopathies include subungual hemorrhage, onycholysis, and onychotillomania.

The specific sign of traumatic onycholysis is the presence of a linear edge of the proximal margin of the onycholysis, without spikes, round hemorrhagic spots or splinter hemorrhages that indicate the traumatic origin [Figure 7]a.{Figure 7}

In onychotillomania, scaling and crusting of nail folds, shortening of nail plate, exposure of nail bed epithelium and presence of hemorrhages are seen on onychoscopy [Figure 7]b.[27]

To conclude, onychoscopy assists in the analysis and differentiation of many dermatoses, which affect nail unit with similar clinical manifestations. It is a rapid and quick diagnostic method that helps physicians to make accurate diagnosis of a given lesion of nail. Thus, it is important to follow the stepwise approach in analyzing the onychoscopic patterns for better patient care.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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