Clinical Dermatology Review

SYMPOSIUM: BASICS OF DERMOSCOPY AND DERMOSCOPIC PATTERNS
Year
: 2020  |  Volume : 4  |  Issue : 2  |  Page : 79--83

Dermoscopic approach to hypopigmentary or depigmentary lesions in skin of color


Balachandra S Ankad, Varsha R Koti 
 Department of Dermatology, S N Medical College, Bagalkot, Karnataka, India

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

Abstract

Introduction: Hypopigmented or depigmented lesions are considered as important dermatoses in daily practice. Their accurate diagnosis is very much crucial because of social stigma attached to these diseases in Indian subcontinent. Authors have proposed basic guidelines for dermoscopic assessment in terms of approach to a given hypopigmented/depigmented lesion. The following conditions are dermoscopically described here, they are vitiligo, idiopathic guttate hypomelanosis, lichen sclerosus, pityriasis alba, leprosy, pityriasis versicolor and nevus depigmentosus. Aim: To propose basic dermoscopic guidelines in terms of approach of a hypopigmented/ depigmented lesion in skin of color. Summary: Dermoscopic patterns highly depend on melanin skin layers and thus analysis of dermoscopic patterns in hypopigmented/depigmented lesions is difficult owing to the reduction or absent melanin in the epidermis. All hypopigmented/depigmentary conditions are described based on the 5 dermoscopic parameters which include; i) background colour, ii) vessels, iii) scales, iv) follicular findings and v) specific clues. Glowing white color in vitiligo and pale or dull white color in IGH and white with little brownish color in PA and PV are the different shades of color in the background in dermoscopy. In leprosy, PMH and ND, background color is brownish-white rather white. LSEA, color is white with bluish or pinkish hue is observed. Furthermore, dermoscopic diagnosis should be based on every parameter visible in a given lesion and not in isolation as each pattern or parameter is immensely contributory to the final diagnosis. Conclusion: Thus, dermoscopy aids in the distinction of hypopigmented/depigmentary lesions by demonstrating characteristic and definitive patterns.



How to cite this article:
Ankad BS, Koti VR. Dermoscopic approach to hypopigmentary or depigmentary lesions in skin of color.Clin Dermatol Rev 2020;4:79-83


How to cite this URL:
Ankad BS, Koti VR. Dermoscopic approach to hypopigmentary or depigmentary lesions in skin of color. Clin Dermatol Rev [serial online] 2020 [cited 2020 Sep 21 ];4:79-83
Available from: http://www.cdriadvlkn.org/text.asp?2020/4/2/79/292481


Full Text



 Introduction



Hypopigmented or depigmented lesions are considered as important dermatoses in daily practice. Their accurate diagnosis is very much crucial because of the social stigma attached to these diseases in the Indian subcontinent. Dermoscopy in hypo/depigmented lesions is limited to case reports and case series. As in inflammatory conditions, there are no defined dermoscopic criteria in hypo/depigmented lesions. Hence, the authors have proposed basic guidelines to the clinician in terms of approach to a given hypo/depigmented lesion.

 Vitiligo



Dermoscopic patterns in vitiligo include a diffuse white structureless area, which is seen as “white glow” due to absent pigment network because of the absence of melanocytes in the lesions [Figure 1]a. Reduced, residual, perifollicular, and perilesional pigmentation are noted based on the evolving, stability, and treatment of the lesions.[1] “Reverse pigment network” which is a feature of melanoma and melanocytic nevus, can be observed in evolving vitiligo. It describes the reverse of normal reticular pigment network, wherein white lines segregate hyperpigmentary areas in net-like fashion. This is exactly opposite to the normal network, and it is noted in evolving lesions of vitiligo and can obviate the need for biopsy in doubtful lesions of vitiligo.[1]{Figure 1}

According to the basic guidelines, milky white is the background color, scales are absent in the lesion, different shades of pigmentation are the pigment pattern, no vascular structures are noted, and white hairs, if present in leukotrichia in vitiligo patch, are the follicular changes. “White glow” forms a special clue in vitiligo as it is not seen in other depigmentary lesions except in idiopathic guttate hypomelanosis (IGH).[2]

 Idiopathic Guttate Hypomelanosis



Four different dermoscopic patterns have been described in IGH and that includes amoeboid, feathery, petaloid, and nebuloid patterns based on the different angulations of white areas at the periphery. In the amoeboid pattern, diffuse structureless white areas extend like pseudopods appearing as as amoeba. Feather-like spreading of margins, is referred to as feathery pattern. The petaloid pattern is characterized by well-defined borders resembling petals of a flower. Nebuloid pattern is distinctive of all with ill-defined borders. It should be noted that the last pattern closely resembles guttate vitiligo. It should be noted that in all types, margins are well demarcated.[3]

Two distinct dermoscopic patterns such as cloudy-sky like and cloudy patterns are described in IGH in Fitzpatrick skin Types I, II, and III.[4] This difference is probably attributable to the color of the skin and duration of lesions.

In all the described patterns, basic dermoscopic features are white structureless areas that extend peripherally in different shapes [Figure 1]b. White structureless areas are due to reduced melanin in the epidermis.[2] Perifollicular, perilesional pigmentation, and diffuse pigmentation with linear and branching vessels are infrequently observed.[2],[4] Pigmentation is more conspicuous in the skin of color.

Notably, bright white, perifollicular and perilesional pigmentation pattern, linear vessels (though infrequent) constitute the background color, pigment, and vascular pattern, respectively. No changes are seen in terms of scaling or follicular structures. Angulated and well-defined borders are the special clue in IGH.

 Lichen Sclerosus Et Atrophicus



Dermoscopy of lichen sclerosus et atrophicus (LSEA) demonstrates different features in early inflammatory and late sclerotic lesions. Inflammatory lesions show white structureless areas, comedo-like openings, linear telangiectasia with variable diameter, and peppered arrangement of gray-blue and brown dots [Figure 1]c, which correspond to the dermal fibrosis, follicular plugs, capillary dilatation and epidermal as well as dermal melanophages respectively.[5],[6] In late lesions, white structureless areas with chrysalis strands are seen with occasional branching telangiectasia of variable diameter and black or gray dots.[5],[6]

It should be noted that chrysalis strands are reflactile white structures due to collagen in the dermis and are observed only with polarized lights.[7] Ano-genital lesions show similar patterns but with more prominent vascular patterns on a diffuse whitish background [Figure 1]d. Dotted vessels were observed in the early stage of the disease. Whitish to pink-whitish structureless areas on white background was a distinctive and constant dermoscopic feature. Scales are distinctly absent over the lesions.[8]

Hence, white is the background color, linear and branching telangiectasia are the vascular structures, comedo-like structures are follicular changes, black and blue-gray globules are pigment patterns and with no scales. We believe, probably, white chrysalis strands are the special clue in LSEA.

 Pityriasis Alba



Dermoscopy in pityriasis alba (PA) is not much studied. Few reports describe white structureless areas with ill-defined margins. Fine scales are noted at the center of the lesion. Areas of faint brownish pigment network are present within whitish areas [Figure 1]e. It is essential to note that scales are white and focally distributed and are not prominent in skin cleavage lines. This particular dermoscopic feature differentiates PA from pityriasis versicolor (PV).

Thus, in the view of basic guidelines, brownish-white is background color, scales are white and focal, light brown pigment network forms the pigment pattern. No follicular and vascular changes are noted in PA without any special clue.[2],[9]

 Leprosy (Hypopigmented Patch)



Dermoscopy demonstrates definitive patterns in hypopigmented patches of leprosy. Dermoscopic patterns include white areas, subtle brownish pigment network with distortion, reduced white dots (eccrine and follicular openings), and hair changes such as pigtail hairs, short or broken hairs, V-like hairs [Figure 2]a. No scales are visible. Vascular changes are not observed in flat hypopigmented patches of leprosy as vascular structures are destroyed by granuloma. However, raised (plaque, nodules, reactional lesions) and facial lesions reveal vascular elements due to inflammation and rich vascularity, respectively. Hence, yellow globules with telangiectasia, which characterize dermoscopic pattern a granuloma, are not observed in leprosy patches except in facial and raised lesions in extra-facial lesions.[10],[11]{Figure 2}

Interestingly, skin cleavage lines in involved skin are widened. White areas are located over the entire lesion or distributed focally or situated in perifollicular areas.

Thus, the background color is brownish-white, pigment pattern is distorted pigment network, and the above-mentioned hairs deformities constitute the follicular changes. As mentioned earlier, no vascular structures and scales are observed in flat hypopigmented (facial) lesions. Authors believe reduced white dots of eccrine and follicular openings are the special clue in leprosy.

 Pityriasis Versicolor



Vitiligo, PA, indeterminate leprosy and progressive macular hypomelanosis (PMH) appear similar to hypopigmented lesions of PV.[2] Dermoscopy provides useful morphological information for the clinical diagnosis as well as to differentiate PV from other hypopigmented lesions. It shows diffuse white structureless areas with faint pigment network in the background [Figure 2]b. Borders of the lesion are indistinct. Fine white scales cover the entire lesions. However, scaling can be present as focal or in perifollicular or perilesional areas and in the skin cleavage lines.[12],[13] Scales in the skin furrows detach from the skin and breaks into two parts when the lesions are stretched. Authors refer it as “double-edged” scales.[2]

Hence, in accordance with basic guidelines, brownish-white in the background color, faint brownish pigment network is the pigment network and scales are fine and white. No follicular and vascular structures are involved in PV. We consider “double edged” scales are the special clue in PV as this pattern is not observed in other hypopigmentary lesions.

 Nevus Depigmentosus



Dermoscopy helps in the differentiation of nevus depigmentosus (ND) from vitiligo and ash leaf macule and other hypopigmented conditions.[14] Dermoscopy of ND shows white structureless areas, faint uniform reticular pigment network throughout the lesion with perifollicular pigmentation [Figure 2]c.[15] White structureless area extends peripherally as pseudopods. These correspond to the serrated borders of ND. In general, white areas under dermoscopy suggest decreased melanin in the epidermis. Here, the presence of faint or subtle uniform reticular pigmentation suggests that melanin is definitely present in the epidermis. This feature of ND gives affirmation to the fact that melanosomes are not transferred to the keratinocytes in ND even though number melanocytes are normal.

Hence, in the view of basic guidelines, brownish-white is the background color, reticular pigment network, and perifollicular pigment are the pigment pattern without scales. Follicular and vascular changes are not seen in ND. We think pseudopod like extensions of the central white structureless area is the special clue in ND.

 Progressive Macular Hypomelanosis



Clinically PMH presents as nonscaly hypopigmented macules that coalesce to form patches. There is symmetry in the distribution of lesions that involve trunk and back.[16] It is crucial to distinguish PMH from vitiligo, and hypopigmented patches of leprosy as therapeutic modalities are entirely different in these conditions. In addition, fear of social outcasting, due to white-colored lesions, plays an important role in the patient's psyche. Hence, an accurate diagnosis is of utmost importance.

Dermoscopy of PMH not described in the literature except for the personal observation by the authors in a review publication, in which they have mentioned ill-defined whitish areas without scaling.[9] In PMH, focal or diffuse whitish areas with subtle reticular pigment at the background are noted. White scales are minimal and absolutely restricted to skin cleavage lines [Figure 2]d.

Hence, in the line of basic guidelines, brownish-white color is the background, white scales are located in skin furrows, and faint reticular pigment network is the pigment pattern with no follicular involvement. We propose that the restriction of scales to skin lines is a special clue in PMH.

In the summation, dermoscopic patterns highly depend on melanin skin layers, and thus, the analysis of dermoscopic patterns in hypo/depigmented lesions is difficult owing to the reduction or absent melanin in the epidermis. Yet, different shades of white color are appreciated, which are contributory to the dermoscopic diagnosis [Table 1]. In a nutshell, glowing white color in vitiligo and pale or dull white color in IGH is due to total or subtotal absence of melanin and a significant reduction in melanocytes, respectively. White with little brownish color in PA and PV is due to hyperkeratosis and reduction in the melanin in the epidermis. In leprosy, PMH and ND, background color is brownish-white rather white because of either an insignificant decrease in melanin (by any means). In LSEA, color is white with bluish or pinkish hue is due to collagen with melanin and dilated capillaries in the dermis.{Table 1}

Furthermore, the dermoscopic diagnosis should be based on every parameter visible in a given lesion and not in isolation as each pattern or parameter is immensely contributory to the final diagnosis. Thus, dermoscopy aids in the distinction of hypopigmented lesions by demonstrating characteristic and definitive patterns.

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Conflicts of interest

There are no conflicts of interest.

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