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Table of Contents
ORIGINAL ARTICLE
Year : 2013  |  Volume : 1  |  Issue : 1  |  Page : 22-29

Clinical and ultrastructural study of nevus depigmentosus


1 Dermatology & Venereology Department, Faculty of Medicine, Tanta University, Egypt
2 Histology Department, Faculty of Medicine, Tanta University, Egypt

Date of Web Publication24-Jan-2018

Correspondence Address:
Arwa M Hassan
Dermatology & Venereology Department, Faculty of Medicine, Tanta University
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.1016/j.jmau.2013.06.006

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  Abstract 


Background: Nevus depigmentosus is a congenital, non-progressive, hypopigmented macule or patch that is stable in its relative size and distribution throughout life. The lesions are often single but may be multiple, circumscribed and either isolated, dermatomal or in whorls. The lesions are uniformly hypomelanoic but not amelanotic. The aetiopathogenesis of nevus depigmentosus is not yet fully understood. A defect in the transfer of melanosomes from melanocytes to keratinocytes has been reported.
Objective: This work aimed at evaluation of the clinical and ultrastructural characteristics of nevus depigmentosus in a trial to understand its pathogenesis.
Patients and methods: This study included 15 patients having nevus depigmentosus. Ultrastructural study was performed for 5 patients. 2 punch biopsies were taken from each patient, one from the center of the lesion and another from the nearby apparently normal skin as a control.
Results: The lesions were mostly present before 3 years of age, mostly on the trunk. Six patients (40%) had the isolated type and 9 (60%) had the segmental type. Under Wood's lamp, the lesions exhibited an off-white accentuation without fluorescence. Ultrastructural study showed apparent reduction in melanosomal content of lesional melanocytes and keratinocytes. Immature and aggregated melanosomes were more present in lesional keratinocytes. Electron microscopic DOPA oxidase reaction was decreased in lesional skin compared to control indicating a reduced tyrosinase activity.
Conclusion: The results of this study support the hypothesis that nevus depigmentosus is caused by functional defect of melanocytes and morphologic abnormalities of melanosomes.

Keywords: Nevus depigmentosus, Congenital, Hypopigmented macule, Ultrastructural, Melanosomes


How to cite this article:
Hewedy ESS, Hassan AM, Salah EF, Sallam FA, Dawood NM, Al-Bakary RH, Al-Sharnoby HA. Clinical and ultrastructural study of nevus depigmentosus. J Microsc Ultrastruct 2013;1:22-9

How to cite this URL:
Hewedy ESS, Hassan AM, Salah EF, Sallam FA, Dawood NM, Al-Bakary RH, Al-Sharnoby HA. Clinical and ultrastructural study of nevus depigmentosus. J Microsc Ultrastruct [serial online] 2013 [cited 2020 Apr 6];1:22-9. Available from: http://www.jmau.org/text.asp?2013/1/1/22/223894




  1. Background Top


Nevus depigmentosus (ND) or achromic nevus is defined as a congenital, non-progressive, hypopigmented macule or patch that is stable in its relative size and distribution throughout life [1]. The lesions are often single but may be multiple, circumscribed and either rounded, dermatomal or in whorls. The lesions are uniformly hypomelanoic but not amelanotic, and they become more apparent with a Wood's lamp examination, by which the lesion shows an off-white accentuation, in contrast to the chalky-white accentuation observed in vitiligo [2].

Nevus depigmentosus is an uncommon, appears mostly as a unilateral hypopigmented macular patch with irregular, serrated borders, and as a role, the lesions do not cross the midline [3]. In most patients there is a single lesion on the trunk or proximal portion of the extremities [4]. Poliosis can be present (6%) [5]. Evidence for a neurocutaneous disorder is limited to a few reports of associated seizures and mental retardation. Unilateral hypertrophy of the extremities on the same side of ND has been described [4].

Clinical diagnostic criteria commonly accepted and proposed by Coupe [6] include leukoderma which present at birth or onset early in life; no alteration in distribution of leukoderma throughout life; no alteration in texture, or change of sensation, in the affected area; and no hyperpigmented border around the achromic area. The hypopigmentation is permanent and enlarges in proportion with growth in the person and no effective treatment is available yet [7].

There are three clinical variants; the commonest is the single, circumscribed, rounded or oval lesion. Segmental (dermatomal) ND can be seen. Systematized form is very rare, and may resemble hypomelanosis of Ito (whorls or streaks predominantly in a unilateral pattern) [8].

According to the size of the diameter of ND lesions, it is frequently divided into type IND simplex in which the lesion is <10 cm without any other findings; type II ND simplex in which the lesion is >10 cm also without associated findings. If there are associated abnormalities, then one speaks of type I and type II ND complex respectively [9].

Type I ND is the most common localized depigmentation seen in healthy newborns. Type I ND simplex should be distinguished from a nevus anemicus. Type II ND simplex develops during early childhood and presents with a checkerboard pattern or in a linear pattern. It should be differentiated from segmental vitiligo [9].

The differential diagnosis of ND includes segmental vitiligo, nevus anemicus, ash leaf spot, and hypomelanosis of Ito. Rarely, the differential diagnosis of ND needs to be made with other conditions associated with hypopigmentation following Blaschko lines as lichen striatus, epidermal nevus and linear keratosis follicularis [10].

The aetiopathogenesis of ND is not yet fully understood [10]. The histologic findings by light microscopy show either a normal number or a decreased number of melanocytes [2]. Electron microscopy can detect a large reduction in the number of melanosomes and aggregated melanosomes of variable morphology. A decrease in the synthesis and transfer of melanosomes has been observed; however, the size and degree of melanization of the melanosomes are normal [1].

1.1. Aim of the work

This work aimed at evaluation of the clinical and ultrastructural characteristics of nevus depigmentosus in a trial to understand its pathogenesis.


  2. Patients and methods Top


2.1. Patients

This study was carried out on 15 patients having nevus depigmentosus (ND). They were collected from the Outpatient Clinic of the Dermatology and Venereology Department of Tanta University Hospital. These patients fulfilled the criteria proposed by Coupe [6] and Xu et al. [10] for clinical diagnosis of ND. These criteria are: (i) leucoderma present at birth or onset early in life; (ii) no alteration in distribution of leucoderma throughout life, except for possible change in size as patient grows; (iii) no alteration in texture or sensation in the affected area; (iv) no hyperpigmented border around the achromic area, but rather an irregular border with no poliosis present; (v) off-white patch without fluorescence under Wood's lamp.

2.2. Methods

The patients were subjected to the following: complete history taking thorough general and cutaneous examination, Wood's lamp examination (Waldmann W)TM, Ultrastructural study.

After an interview with the parents and a written consent, 2 punch biopsies, 3 mm each, were taken from each patient, one from the center of the lesion and another from the nearby apparently normal skin as a control. Each specimen was divided into two parts. The first part was fixed in 10% formalin and was processed in paraffin. Microtome sections (6 μm thickness) were stained by hematoxylin and eosin (H&E) stain for routine histopathology. The second part was processed for ultrastrucural evaluation to detect the morphologic alterations of melanocytes and keratinocytes.

2.3. Ultrastructural study

2.3.1. Preparation of semithin and ultrathin sections

The skin specimens were divided by a sharp razor blade into small pieces of 1 mm3 in size and subjected to certain steps for preparation of semithin and ultrathin sections according to Dawes [11], and Hayat [12].These steps were: fixation, dehydration, infiltration with the epoxy resin mixture, embedding and polymerization sectioning.

2.3.2. Staining of the grids for ultrastructural examination

In order to impart contrast into the ultrathin sections when viewed in the transmission electron microscope (TEM), the mounted sections were double stained, first with uranyl acetate solution for 30 min and washed in three changes of distilled water, then stained with lead citrate for 5–10 min, washed with distilled water and dried upon clean filter paper. Finally, each grid was examined and photographed with JE0L-JEM-100SX electron microscope at 80-Kilo vol.

2.3.3. Electron microscopic-DOPA reaction test

The tyrosinase activity in epidermal melanocytes was evaluated by the EM-DOPA reaction test [13]. The skin samples were fixed with 2% glutaraldehyde and incubated in 0.1% DOPA/phosphate buffer for 5 h at 37 °C. The samples were then postfixed in 1% osmium tetroxide for 2 h. After dehydration, the specimens were embedded in Epon. Ultrathin sections were cut and examined by TEM.


  3. Results Top


3.1. Clinical results

This study included 15 ND patients, 9 (60%) males and 6 (40%) females. The age of the patients ranged from 6 months to 16 years with a mean value ± SD of 8.51 ± 4.89 years. The age of onset was at birth in only one patient (6.67%), while the latest was in 2 patients (13.33%) where the lesions appeared after the age of 3 years, [Table 1]. The trunk (front and back) was the most commonly affected site, as 46.67% of the lesions were on the trunk while the neck was the least affected site (13.33%) [Table 2]. Of the studied 15 patients, 6 (40%) had the isolated type and 9 (60%) had the segmental type. No patient showed the systematized form of ND. In all patients the lesions appeared as hypopigmented patches with irregular, serrated border [Table 1] and [Table 2] and [Figure 1] and [Figure 2]. All patients did not show cutaneous lesions other than ND, and no apparent congenital anomalies were observed.
Table 1: Age distribution and clinical patterns of ND in the studied patients.

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Table 2: Distribution of ND lesions according to clinical patterns and sites.

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Figure 1: A 9-years old male patient with isolated pattern of ND on the neck, the lesion has irregular, serrated border.

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Figure 2: A 1-year old female infant with dermatomal type of ND on the Lt side of the trunk. (A) Shows the front and (B) Shows the back.

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3.2. Appearance under Wood's lamp

Under Wood's lamp examination, the lesion of ND showed an off-white accentuation without fluorescence [Figure 3], in contrast to the chalky-white accentuation with obvious bluish white fluorescence observed in vitiligo patients.
Figure 3: (A) A 5-years old male patient with dermatomal type of ND on the neck. (B) The same lesion under Wood's light, the lesion shows an offwhite accentuation without fluorescence.

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3.3. Histopathological results

Hematoxylin and Eosin staining of the biopsies obtained from the lesional skin of the studied patients showed the same results. There was a decrease in melanin content of the epidermis, compared to the apparently normal perilesional skin (control skin) [Figure 4] and [Figure 5]. There was also a focal perivascular and periadenexal lymphocytic infiltration in the superficial layer of the dermis [Figure 6].
Figure 4: Control skin (H&E 400×).

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Figure 5: Lesional skin showing decreased melanin content, the presence of melanocytes is clear within the basal layer (H&E 400×).

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Figure 6: Lesional skin showing focal perivascular lymphocytic.

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3.4. Ultrastructural results

Ultrastructural study of the biopsies obtained from the lesional skin of the studied ND patients showed the same results with variable degrees. The melanocytes of both control and lesional skin were normal in shape (mature melanocytes). Compared to the control skin, lesional skin showed apparent reduction in melanosomal content in the melanocytes and keratinocytes of ND lesions, immature and aggregated melanosomes were more often observed in keratinocytes of ND lesions. In control skin, melanosomes were mainly supranuclear, while in lesional skin melanosomes were dispersed all around the nucleus and were surrounded by increased tonofilaments which form a mesh entrapping them. Some of the lesional keratinocytes showed dilated perinuclear envelop, large cytoplasmic vesicles, nuclei with deep indentation, and clumped condensed nuclear chromatin [Figure 7],[Figure 8],[Figure 9],[Figure 10],[Figure 11],[Figure 12],[Figure 13],[Figure 14].
Figure 7: Electron micrograph (EM) of control skin showing mature melanosomes (arrows) in a keratinocyte (K). These melanosomes are mainly located in the supranuclear region (2000×).

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Figure 8: EM of lesional skin of the same patient showing marked reduction in melanosomal content with abnormal distribution of tonofilaments (arrows) which forming mesh entrapping melanosomes around the nucleus (N) in various stages of maturation (2000×).

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Figure 9: EM of control skin showing normal melanocyte (M) resting on the basement membrane (black arrows). The melanocyte contain multiple mature (stage IV) melanosomes (red arrows) which are mainly located in the supranuclear region (1500×).

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Figure 10: EM of lesional skin of the same patient showing normal melanocyte (M) resting on the basement membrane (black arrows). The melanocyte shows apparent decrease in melanosomal content. These melanosomes are mainly immature (red arrows) (2500×).

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Figure 11: EM of lesional skin showing marked reduction in melanosomal content within the epidermal cells with marked increase in tonofilaments (black arrows). Red arrows point to immature melanosomes (1500×).

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Figure 12: EM of lesional skin showing clumped condensed nuclear chromatin (arrows) of a keratinocyte (K) (2500×).

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Figure 13: EM of lesional skin showing dilated perinuclear envelop (arrow) and large cytoplasmic vesicle (V). The melanosomes are apparently decreased (2500×).

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Figure 14: EM of lesional skin showing deep indentation of the nucleus of a keratinocyte (K) and aggregated melanosomes around the nucleus (arrows) (3000×).

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3.5. Electron microscopic-DOPA reaction test

EM-DOPA reaction is decreased in lesional skin compared to control skin. After incubation with DOPA solution, most of the melanosomes of control skin changed to stage IV melanosomes. On the other hand, some of the immature melanosomes of lesional skin changed to stages III and IV, but stages I and II melanosomes were also seen indicating a reduced tyrosinase activity [Figure 15],[Figure 16],[Figure 17].
Figure 15: EM of DOPA-oxidase reaction in control skin showing different stages of melanosomal maturation mainly mature melanosomes stage IV (2000×).

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Figure 16: EM-DOPA reaction of lesional skin of the same patient showing apparent decrease in melanosomal content which are mainly immature (arrows) (2500×).

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Figure 17: EM of DOPA-oxidase reaction in lesional skin showing different stages of melanosomal maturation mainly immature melanosomes stage II (black arrows). Stage III melanosomes (red arrows) are also present (4000×).

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  4. Discussion Top


Although the clinical features of ND may initially appear similar to those of vitiligo, the clinical course of ND and vitiligo differs. Misdiagnosis of ND as vitiligo may lead to tremendous psychologic trauma and economic loss. On the other hand, misdiagnosis of vitiligo as ND may lead to failure of treatment at the appropriate time.

All patients included in this study fulfilled the clinical diagnostic criteria for ND proposed by Coupe [6].The development of ND usually takes place at an early age. However, sporadic reports have suggested its initial presentation at various ages [1]. According to the results of the present study, early onset is an important feature of ND. Of the studied 15 patients, 40% had lesions before 1 year of age, and 73.33% had the initial lesion before the age of 3 years, coincident with the age of onset reported in the literature [1],[10]. For this reason a diagnosis of ND should be considered when a patient develops a hypopigmented macule at an early age [10].

Because the white spot in ND is slightly off-white when compared with vitiligo and the lesion generally appears in infants or young children who usually have untanned skin, the color contrast may not be readily visible. This makes it prone to late discovery in some cases. Accordingly, it was hypothesized that there is a correlation between dark-skinned persons and early detection and between fair-skinned persons and delayed detection [1]. The male to female ratio in this study was 3:2. This may be related to the random collection of patients.

Many researchers [10],[14] reported that the most common site of ND is the trunk. The results of this study coincide with this finding where the trunk was involved in 46.67% of the patients followed by the lower and upper limbs (20% for each), and lastly the neck (13.33%). Most of the studied patients showed only one lesion (80%), whereas in vitiligo, the lesions always appear on the exposed parts, and developed at several locations [14]. The studied patients exhibited that ND lesions had irregular shape and serrated border, as described by Lee et al. [1] and Xu et al. [10]. These features are helpful to differentiate ND from vitiligo.

It is generally agreed that the classification of ND should be divided into isolated, segmental, and systematized (whorled) types [8]. In this study, 6 patients (40%) had the isolated type, 9 patients (60%) had the segmental type, and none of the patients showed the systematized form of ND. Wood's lamp examination was a useful method to discriminate between ND and vitiligo in this study.

In this study, all patients did not show cutaneous lesions other than ND, and no apparent congenital anomalies were observed. However, many researchers reported cases with associated cutaneous and systemic manifestations in ND patients [15],[16],[17],[18],[19].

In this study by H&E examination, the epidermis demonstrated the presence of melanocytes, in contrast to vitiligo, and decreased melanization of the basal cell layer in lesional skin compared to control skin. Upper dermis showed focal perivascular and periadenexal lymphocytic infiltration. EM examination was done for ND patients to illustrate ultrastructure of the lesional skin in comparison with the apparently normal perilesional skin, control skin, in an attempt to detect the pathogenesis of ND. The lesions showed the presence of mature melanocytes which means that the disease is not caused by absence of melanocytes and that ND is a hypomelanotic and not a hypomelanocytic disorder. This was agreed by many authors [1],[3],[4],[5],[8],[10].

The present study demonstrated defective melanogenesis in the lesional skin of the studied patients. The melanosomes were mainly immature. Also, there was abnormal distribution of the melanosomes all around the nucleus in contrast to the control skin where the melanosomes were mainly supranuclear. Lesional skin showed increased tonofilaments which act as a mesh entrapping the melanosomes perinuclear.

Lee et al. [1] and Xu et al. [10] did ultrastructural study for ND in 8 and 4 patients respectively. They exhibited the presence of aggregated melanosomes in the keratinocytes of lesional skin. The present study showed the same finding. It seem that degeneration of melanosomes in keratinocytes may relate to the pathogenesis of ND.

In the present study, some of the lesional keratinocytes showed large perinuclear cytoplasmic vesicles, this finding has been shown also by Xu et al. [10]. To our knowledge, there is no explanation for this finding.

Ultrastructural study using EM-DOPA technique was done to demonstrate the status of tyrosinase activity in ND patients. After incubation with DOPA solution, most of the melanosomes of control skin changed to stage IV melanosomes. On the other hand, some of the immature melanosomes of lesional skin changed to stages III and IV, but stages I and II melanosomes were also seen indicating a reduced tyrosinase activity. To our knowledge, there are no available references about the study of EM-DOPA technique in ND.

From the results of this study which showed the presence of mature melanocytes in ND lesions, it may be possible to achieve repigmentation of ND by stimulation of melanogenesis using phototherapeutic modalities as recommended by Scott et al. [20]. Also, excimer laser can affect ND. Park et al. [21] treated a 5 years old boy with ND by a 308-nm excimer laser and observed marked improvement of the ND lesion. Surgical therapeutic attempts to achieve repigmentation can be used such as an autologous graft with melanocytes or a conventional epidermal graft [21].

Conflict of interest

We have no conflict of interest to declare.



 
  References Top

1.
Lee HS, Chun YS, Hann SK. Nevus depigmentosus: clinical features and histopathologic characteristics. Journal of the American Academy of Dermatology 1999;40:21-6.  Back to cited text no. 1
    
2.
Kim SK, Kang HY, Lee ES, Kim YC. Clinical and histopathologic characteristics of nevus depigmentosus. Journal of the American Academy of Dermatology 2006;55:423-8.  Back to cited text no. 2
    
3.
Rubeiz N, Kibbi AG. Disorders of pigmentation in infants and children. Clinics in Dermatology 2002;20:4-10.  Back to cited text no. 3
    
4.
Bolognia JL, Pawelek JM. Biology of hypo-pigmentation. Journal of the American Academy of Dermatology 1988;19:217-25.  Back to cited text no. 4
    
5.
Herane MI. Vitiligo and leukoderma in children. Clinics in Dermatology 2003;21:283-95.  Back to cited text no. 5
    
6.
Coupe RL. Unilateral systematized achromic nevus. Dermatologica 1976;134:19-35.  Back to cited text no. 6
    
7.
Kar BR. Nevus depigmentosus trated with suction blister grafting: follow-up after 10 years. Indian Journal of Dermatology 2013;58(2):158.  Back to cited text no. 7
    
8.
Anstey AV. Disorders of skin colour. In: Burns DA, Breathnach SM, Cox NH, et al., editors. Rook's textbook of dermatology. 8th ed. Wiley-Blackwell; 2010. p. 39-52 [chapter 58].  Back to cited text no. 8
    
9.
Ruiz-Maldonado R. Hypomelanotic conditions of the newborn and infant. Dermatologic Clinics 2007;25:373-82.  Back to cited text no. 9
    
10.
Xu AE, Huang B, Li YW, Wang P, Shen H. Clinical, histopathological and ultrastructural characteristics of nevus depigmentosus. Journal of Clinical & Experimental Dermatology 2008;33:400-5.  Back to cited text no. 10
    
11.
Dawes CJ. Biological techniques for transmission electron microscopy. 1st ed. Ladd Research Industries; 1980. p. 16.  Back to cited text no. 11
    
12.
Hayat MA. Basic techniques for transmission electron microscopy. New York: Harcout Brance Jovanich. Co.; 1987. p. 232.  Back to cited text no. 12
    
13.
Takizawa Y, Kato S, Matsunaga J, Aozaki R, Tomita Y, Nishikawa T, et al. Electron microscopic DOPA reaction test for oculocutaneous albinism. Archives of Dermatological Research 2000;292:301-5.  Back to cited text no. 13
    
14.
Ortonne JP, Mosher DB, Fitzpatrick TB. Vitiligo and other hypomelanoses of hair and skin. New York: Plenum Medical; 1983. p. 398-411.  Back to cited text no. 14
    
15.
In SI, Kang HY. Partial unilateral lentiginosis colocalized with nevus depigmentosus. Clinical and Experimental Dermatology 2007;33:337-55.  Back to cited text no. 15
    
16.
Afsar FS, Aktas S, Ortac R. Becker's nevus and segmental nevus depigmentosus: an example of twin spotting. Australasian Journal of Dermatology 2007;48:224-6.  Back to cited text no. 16
    
17.
Menni S, Betti R, Boccardi D, Gualandri L. Both unilateral nevus achromicus and congenital agminated Spitz nevi in a checkerboard mosaic pattern. British Journal of Dermatology 2001;144:186-221.  Back to cited text no. 17
    
18.
Dippel E, Utikal J, Feller G, Fackel N, Klemke CD, Happle R, et al. Nevi flammei affecting two contralateral quadrants and nevus depigmentosus: a new type of phacomatosis pigmentovascularis? American Journal of Medical Genetics 2003;19A:228-30.  Back to cited text no. 18
    
19.
Sharma P, Pai HS, Kamath MM. Nevus depigmentosus affecting the iris and skin: a case report. Journal of the European Academy of Dermatology and Venereology 2008;22:616-50.  Back to cited text no. 19
    
20.
Scott G, Deng A, Rodriguez-Burford C, Seiberg M, Han R, Babiarz L, et al. Protease activated receptor 2, a receptor involved in melanosome transfer, is upregulated in human skin by ultraviolet irradiationk. Journal of Investigative Dermatology 2001;117:1412-20.  Back to cited text no. 20
    
21.
Park YK, Kim DY, Lee KY. Use of the 308-nm excimer laser for nevus depigmentosus: a promising treatment for either nevus depigmentosus or vitiligo. Journal of Dermatology 2007;34:217-8.  Back to cited text no. 21
    


    Figures

  [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]
 
 
    Tables

  [Table 1], [Table 2]


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