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DERMATOPATHOLOGY ROUND
Year : 2014  |  Volume : 59  |  Issue : 6  |  Page : 571-574
Skip areas of retained melanin: A clue to the histopathological diagnosis of idiopathic guttate hypomelanosis


Department of Dermatology, P. D. Hinduja Hospital, Mahim, Mumbai, India

Date of Web Publication30-Oct-2014

Correspondence Address:
Dr. Rajiv Joshi
14 Jay Mahal, A Road, Churchgate, Mumbai-400 020
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5154.143516

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   Abstract 

Biopsy findings in 55 cases of idiopathic guttate hypomelanosis (IGH) are reported. Most cases had a flat epidermis with loss of the rete pattern and a thickened orthokeratotic basket weave stratum corneum. The epidermis had markedly decreased to absent melanin in the basal layer and reduced numbers of melanocytes at the dermoepidermal junction. One-third of patients had a sparse perivascular lymphocytic infiltrate, whereas the rest had no significant dermal inflammation. These findings are in concordance with current literature.However, small foci of retained melanin in the basal layer (skip areas) alternating with larger areas of melanin loss were present in almost 80% of cases. This finding has not been reported earlier and appears to be quite specific to IGH and may be used as a clue to differentiate IGH from other similar conditions such as vitiligo and guttate morphea.


Keywords: Idiopathic guttate hypomelanosis, melanin retention, skip areas


How to cite this article:
Joshi R. Skip areas of retained melanin: A clue to the histopathological diagnosis of idiopathic guttate hypomelanosis. Indian J Dermatol 2014;59:571-4

How to cite this URL:
Joshi R. Skip areas of retained melanin: A clue to the histopathological diagnosis of idiopathic guttate hypomelanosis. Indian J Dermatol [serial online] 2014 [cited 2021 Aug 5];59:571-4. Available from: https://www.e-ijd.org/text.asp?2014/59/6/571/143516

What is known?
Idiopathic guttate hypomelanosis shows flat epidermis with basket weave stratum corneum and markedly decreased or absent melanin in the basal layer, which is histologically difficult to differentiate from vitiligo.



   Introduction Top


Idiopathic guttate hypomelanosis (IGH) is a common leukodermic dermatosis that affects middle-aged and elderly people with a slight female preponderance and possible familial aggregation. [1] Indian studies of geriatric population have shown IGH to occur in between 43% [2] and 76.5% [3] of patients. Clinically IGH presents as few scattered depigmented sharply marginated macules with sharp angles, varying in size from 2 to 10 mm. The extensor forearms and shins are commonly affected but other regions of the body such as the abdomen and chest may also be affected. Lesions of IGH on the face have been described [4] ; however, this new finding needs validation by other workers. The cause of IGH is unknown, but photoaging and UV-induced damage both actinic and iatrogenic have been implicated in its pathogenesis. [5] One hypothesis suggests that early aging of skin or somatic mutations of melanocytes may result in IGH. [1]

Histological findings include a flat epidermis with absence of the rete ridges and a basket weave stratum corneum. There is markedly decreased to absent melanin in the basal layer and decreased numbers of (but not absent) melanocytes at the dermoepidermal junction. A light microscopic and ultrastructural study [6] showed reduced numbers of dopa-positive melanocytes with fragmented or absent dendrites and reduced numbers of melanosomes. Depigmentation in IGH possibly occurs in two stages: first initially there is a loss of melanogenic activity followed later by elimination of inactive melanocytes. [7]

IGH by itself is only a cosmetic blemish and usually ignored by most people who have it, however, in societies where vitiligo is considered a social stigma, IGH may coexist with patches of vitiligo or be mistaken for vitiligo and cause severe anxiety to patients and their relatives.

Histological findings in IGH may resemble those seen in vitiligo and definite differentiation between those two entities may not be possible, especially in acrally located guttate lesions of vitiligo.

In this histopathological study of 55 patients with IGH, small areas of retained melanin (skip areas) in the basal layer that alternate with broader areas of melanin loss was consistently noted in about 80% of biopsies. This has not been previously reported. This finding seems to be fairly specific for IGH and may be used as a clue for the definite histopathological diagnosis of IGH and its differentiation from vitiligo and other similar conditions such as guttate morphea and guttate Lichen sclerosus.


   Methods and Results Top


This is a retrospective study of biopsy findings of 55 patients rendered a histopathological diagnosis of IGH.The age distribution of patients is presented in [Figure 1].The sites of biopsy were mainly the leg (39), other sites were arm (1), hand (1), forearm (2), chest (2), abdomen (2), back (2), thigh (2), and foot (1). In three patients the site of biopsy was not mentioned.

Fifty-five patients (24 males) had biopsies submitted for a clinical diagnosis of IGH (40), IGH+ other differential diagnoses (5) and other clinical diagnoses, mainly Lichen sclerosus or guttate morphea without IGH as a clinical diagnosis (10). The findings of skip areas of melanin retention or absence of skip areas in these patients is summarized in [Table 1].The histological findings in the 55 patients are summarized in [Table 2].

Skip areas refer to small areas of near normal melanin that are seen in an otherwise depigmented basal layer. The term skip refers to sparing of a small part of the basal layer from depigmentation, which is the dominant pathophysiological process in the epidermis in this disease.

Skip areas may involve broad areas of the basal layer and may be clearly outlined against the adjacent depigmented epidermis [Figure 2] and [Figure 3] or may be very small, subtle, and difficult to see except at high magnification [Figure 4] and [Figure 5].


   Discussion Top


The majority of our patients (35/55) belonged to 30-50 years age group, which is lower than usually described for IGH. The youngest patient was 12 years and the oldest was 76 years. Extensive IGH progressing over few years has been described in a 6-year-old girl. [8]

IGH is clinically often confused with vitiligo and lichen sclerosus. Histologically too, both these conditions show epidermal features that are similar to IGH, namely, a flat epidermis with markedly decreased or absent melanin in the basal layer with decreased numbers of melanocytes at the dermoepidermal junction.

Histopathological findings in vitiligo vary according to the life of the lesion. [9] An early evolving lesion shows decreased melanin in the basal layer with few melanocytes still present at the dermoepidermal junction with a sparse perivascular lymphocytic infiltrate. As the lesion ages the epidermis flattens and there is complete loss of melanin and melanocytes. Findings intermediate to these may be seen and are difficult to differentiate from IGH.

Early lesions of lichen sclerosus too may be difficult to differentiate from IGH as early lesions may not have the characteristic papillary dermal sclerosis, which develops as the lesion ages and presents clinically with surface atrophy.

Skip areas of retained melanin in a flat depigmented epidermis has not been described earlier. This finding was seen in almost 80% of our cases of IGH. In cases where the clinical diagnosis was not IGH the presence of skip areas of retained melanin and absence of dermal sclerosis and inflammation helped to differentiate between IGH and lichen sclerosus.

Dermoscopic findings may provide a basis for the histological findings of skip areas of melanin retention seen in IGH. Dermoscopic findings commonly seen in IGH are the Amoeboid (depigmented to hypopigmented macule with pseudopod-like extensions) and Petaloid (depigmented to hypopigmented macule with polycyclic margins) patterns and photographs of these patterns reveal small specks of pigmentation scattered within the hypo- or depigmented macule in addition to pigmentary extensions at the periphery. [10] It is our hypothesis that the skip areas of retained melanin seen under the microscope correspond to the specks of pigment seen in the center of the IGH macule, a finding that is not mirrored in vitiligo.

Skip areas may be very subtle [Figure 4] and [Figure 5] and may be easily missed if not specifically looked for at high magnification.

Twenty percent of our cases did not show skip areas but had complete loss of melanin in the basal layer, more akin to late stage of vitiligo. The presence of few melanocytes was, however, noted in these cases and based on clinicopathological correlation these cases were most likely IGH.

One patient with clinical diagnosis of IGH showed mild upper dermal sclerosis but also had skip areas of retained melanin without any dermal inflammatory infiltrate and was therefore diagnosed as IGH.

The significance of basal cell vacuolization seen in three cases and solar elastosis seen in four cases is not known.

Based on the findings in these patients, we believe that the histological picture of a flat epidermis with loss of the rete pegs and a thick orthokeratotic basket weave stratum corneum with small skip areas of retained melanin is fairly specific for IGH.

In conclusion, skip areas of retained melanin in a flat depigmented epidermis is a clue for the histological diagnosis of IGH and may be used to differentiate that condition from other similar conditions such as vitiligo and lichen sclerosus.

 
   References Top

1.Falabella R, Escobar C, Giraldo N, Rovetto P, Gil J, Barona MI, et al. On the pathogenesis of idiopathic guttate hypomelanosis. J Am Acad Dermatol 1987;16:35-44.  Back to cited text no. 1
    
2.Sayal SK, Rajbhandari S, Malik AK, Gupta CM. A study of dermatological disorders in geriatric age group. Indian J Dermatol Venereol Leprol 1998;64:270-2.  Back to cited text no. 2
[PUBMED]  Medknow Journal  
3.Grover S, Narasimhalu CR. A clinical study of skin changes in geriatric population. Indian J Dermatol Venereol Leprol 2009;75:305-6.  Back to cited text no. 3
[PUBMED]  Medknow Journal  
4.Shin MK, Jeong KH, Oh IH, Choe BK, Lee MH. Clinical features of idiopathic guttate hypomelanosis in 646 subjects and association with other aspects of photoaging. Int J Dermatol 2011;50:798-805.  Back to cited text no. 4
    
5.Kaya TI, Yazici AC, Tursen U, Ikizoglu G. Idiopathic guttate hypomelanosis: Idiopathic or ultraviolet induced? Photodermatol Photoimmunol Photomed 2005;21:270-1.  Back to cited text no. 5
    
6.Ploysangam T, Dee-Ananlap S, Suvanprakorn P. Treatment of idiopathic guttate hypomelanosis with liquid nitrogen: Light and electron microscopic studies. J Am Acad Dermatol 1990;23:681-4.  Back to cited text no. 6
    
7.Ortonne JP, Perrot H. Idiopathic guttate hypomelanosis. Ultrastructural study. Arch Dermatol 1980;116:664-8.  Back to cited text no. 7
    
8.Mohan L, Mukhija RD, Bhatia PS, Mishra SD, Mishra R. Idiopathic guttate hypomelanosis. Indian J Dermatol Venereol Leprol 1990;56:456-7.  Back to cited text no. 8
  Medknow Journal  
9.Patel AB, Kubba R, Kubba A. Clinicopathological correlation of acquired hypopigmentary disorders. Indian J Dermatol Venereol Leprol 2013;79:376-82.  Back to cited text no. 9
[PUBMED]  Medknow Journal  
10.Bambroo M, Pande S, Khopkar US. Dermascopy in differentiation of IGH and guttate vitiligo. In: Khopkar US, editor. Dermascopy and Trichoscopy in Diseases of the Brown Skin: Atlas and Short Text. New Delhi: J P Brothers Medical Publishers; 2012. p. 97-103.  Back to cited text no. 10
    

What is new?
Skip areas of retained melanin in a fl at depigmented epidermis is a clue to diagnosis of IGH and serves to differentiate that disease from vitiligo and lichen sclerosus.


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2]



 

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    Abstract
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