|Year : 2014 | Volume
| Issue : 2 | Page : 56-58
A brief review of nevus depigmentosus
Samujjala Deb1, Rashmi Sarkar2, Asit Baran Samanta1
1 Department of Dermatology, Venereology and Leprology, Burdwan Medical College and Hospital, Burdwan, West Bengal, India
2 Department of Dermatology, Maulana Azad Medical College, New Delhi, India
|Date of Web Publication||15-Dec-2014|
C-45, New Raipur, Gangulybagan, Kolkata - 700 084, West Bengal
Source of Support: None, Conflict of Interest: None
Nevus depigmentosus is a congenital disorder of pigmentation which occurs in all sexes and races. It commonly presents in childhood and is mostly nonprogressive. It is a form of cutaneous mosaicism with functionally defective melanocytes and abnormal melanosomes. Localized solitary lesions need to be differentiated from conditions like nevus anemicus, ash leaf macule, vitiligo, etc., and generalized lesions from hypomelanosis of Ito. Treatment is usually not required although cosmetic camouflage, phototherapy, grafting, and other modalities may be tried.
Keywords: Cutaneous mosaicism, nevus depigmentosus, childhood
|How to cite this article:|
Deb S, Sarkar R, Samanta AB. A brief review of nevus depigmentosus. Pigment Int 2014;1:56-8
| Introduction|| |
Nevus depigmentosus (ND syn. nevus achromicus) is a rare congenital pigmentary disorder first described by Lesser in 1884.  It is an uncommon birthmark (nevus) classically defined as a congenital nonprogressive hypopigmented macule, stable in size and distribution. The condition is usually limited to the skin but sometimes may be associated with seizures, mental retardation, unilateral limb hypertrophy, atopic dermatitis, and abnormal systemic features. 
| What is It?|| |
It is a circumscribed area of depigmentation which might not be apparent at birth and may continue to appear until adulthood. Individuals belonging to all races and sex can be affected. It increases in size with the growth of the body reaching its maximum dimensions and usually remains stable throughout life thereafter. The lesion is solitary, several centimeters in diameter, with irregular but well-defined serrated borders that do not cross the midline. Often smaller macules arise around the edge giving it a "splashed paint" appearance [Figure 1].
|Figure 1: A 30-year-old lady with large segmental hypopigmented patch on one side of the midline with "splashed paint" appearance|
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| Why does It Occur?|| |
The pathogenesis of ND is not fully understood. It is believed to be due to a functional defect of melanocytes with morphological abnormalities of melanosomes. It is also said to be a form of cutaneous mosaicism wherein an altered clone of melanocyte have a decreased ability to synthesize melanin and transport to keratinocytes.  Melanosomes are usually normal in size, shape, and internal structure, but can be diminished in number, heteromorphic, aggregated in melanocytes, or located in membrane bound aggregates.  The presence of lentigines along with ND may also represent the phenotypic manifestation of reverse mutation.  ND and hypomelanosis of Ito (HOI) can be considered to be the two phenotypic expressions of mosaicism affecting the pigmentary genes. The heterogeneity of genetic anomalies may be due to the presence of multiple loci coding for pigment related proteins. In ND, the somatic mutations occur later during embryogenesis when most structures have already been formed, resulting in fewer systemic manifestations. But in HOI, it is likely that these mutations occur much earlier and thus more body structures are involved (62-94% chance of systemic involvement). 
| What are its Sub-Types?|| |
It can be found anywhere on the body but commonly it is seen on the trunk, neck, face, and proximal part of the extremities. Clinically, three types have been described: Localized, Segmental, and Linear or Whorled. Localized variant is the most common compared to the others. It is a single well circumscribed lesion with serrated borders. Segmental variant is larger in size and shape and also referred to as "segmental depigmentation disorder" with a sharp midline demarcation. It usually occurs as a unilateral streak or patch along the lines of Blaschko. Linear/whorled/systematized type may be extensive and have cutaneous lesions that overlap with HOI. The systematized variant is very rare and may have extra cutaneous manifestations such as seizures, mental retardation, hemi hypertrophy, and yellow hair.  The distinction between whorled ND and HOI is unclear at times. Cases of HOI without extra cutaneous anomalies have often been categorized as ND, whereas cases of ND associated with extra cutaneous anomalies may have been categorized as HOI. In the future, either of these two conditions may be categorized as nevoid hypopigmentation secondary to cutaneous mosaicism. Co-localized lentigines have also been reported in ND. 
| How is It Diagnosed, Differentiated and Treated?|| |
Nevus depigmentosus can be diagnosed using the following criteria given by Coup in 1976. 
- Leukoderma present at birth or of early onset
- No alteration in the distribution of leukoderma throughout life
- No alteration in texture or change in sensation in the affected area
- Absence of hyperpigmented border.
Apart from these, a few other investigations which are help in the diagnosis are: Diascopy test, which is negative (positive in nevus anemicus) [Figure 2] and [Figure 3]. Wood's lamp examination demonstrates an off-white color (chalky white in Vitiligo). Relative melanin index can be measured using a pigment measuring device.  Histopathologic examination shows normal to decreased number of melanocytes with S-100 stain and less reactivity with 3,4-dihydroxyphenylalanine reaction and no melanin incontinence.  Electron microscopic findings show stubby dendrites of melanocytes containing autophagosomes with aggregates of melanosomes. Dermoscopy and in vivo reflectance confocal microscopy are also useful in diagnosing and differentiating ND from other conditions. Computed tomography scan, magnetic resonance imaging, radiography are usually normal and helpful in ruling out other condition if systemic features are present.
|Figure 2: An 8-year-old male patient with single hypopigmented patch over arm since childhood|
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The number of conditions that have a similar appearance and need to be differentiated are given in the following [Table 1]. ,
As far as treatment is considered, mostly it does not require any as it is non-progressive and adequate counseling is sufficient to allay fears about the condition especially among parents concerned about their affected child. Optional treatment modalities include Cosmetic camouflage (especially for lesions on uncovered parts of the body), psoralen-ultraviolet-A therapy, suction blister grafting,  Melanocyte-Keratinocyte transfer, , excimer laser to name a few.
| When should it arouse suspicion?|| |
Isolated and localized solitary lesion usually presents no diagnostic difficulty and may be simply followed up regularly. But the presence of large patches in a whorled or linear distribution with seizures, mental retardation, hearing abnormalities, abnormal dentition, visual and orthopedic abnormality may point toward more sinister causes like HOI. 
| Conclusion|| |
Nevus depigmentosus is a benign congenital pigmentary disorder that can cause significant psychological morbidity among both parents and older patients alike. While thorough and gentle counseling is often sufficient, if the patient desires various treatment modalities may be tried. Careful clinical examination and relevant investigations must be carried out in patients presenting with extensive lesions and in those with internal manifestations especially involving the nervous and musculoskeletal systems. The case has been reported wherein an acquired junctional melanocytic nevus developed in the case of ND.  Interestingly, a single case of spontaneous resolution of ND in a boy has also been reported and thus, it may be fruitful to follow up these patients for a longer duration of time. 
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[Figure 1], [Figure 2], [Figure 3]