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Year : 2011  |  Volume : 56  |  Issue : 6  |  Page : 772-773
Melasma study: Methodological problems


Department of Dermatology, K P C Medical College, Kolkata, India

Date of Web Publication14-Jan-2012

Correspondence Address:
Saumya Panda
Department of Dermatology, K P C Medical College, Kolkata
India
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DOI: 10.4103/0019-5154.91854

PMID: 22345796

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How to cite this article:
Panda S. Melasma study: Methodological problems. Indian J Dermatol 2011;56:772-3

How to cite this URL:
Panda S. Melasma study: Methodological problems. Indian J Dermatol [serial online] 2011 [cited 2014 Oct 23];56:772-3. Available from: http://www.e-ijd.org/text.asp?2011/56/6/772/91854


Sir,

I read with much interest the article "Melasma: A clinico-epidemiological study of 312 cases" by Achar and Rathi,[1] published in the July-August issue. This is an area which has a rather sparse representation, particularly in the Indian literature, despite melasma being a very common disorder in this part of the world. So, this article is a welcome addition to the same.

However, there are certain areas in the article where some clarifications might be in order. In the "Results" section, the authors write: "According to the distribution of lesions, three clinical patterns of melasma were observed and among these, the centrofacial type was the most common, seen in 173 (54.44%) cases. Other types noted were malar 135 (43.26%) and mandibular 5 (1.60%), respectively." It is not clear whether the authors considered some cases to be of composite distribution (e.g. malar + mandibular) because the figures do not add up otherwise. If each case is taken to belong to a discrete morphological subtype, the total number of cases goes up to 313. Given that composite distribution patterns are yet to be acknowledged in the literature and that the authors of this article too have not made any comments in this regard, this discrepancy needs be sorted out.

Despite the arithmetic uncertainty about the exact number of different morphological subtypes, there would be some cases who the authors would brand as mandibular melasma. This is problematic because the authors have not done histopathology in any of the cases. In the literature, globally as well as in India, melasma in the mandibular distribution has been described very rarely. If we take histopathologic studies into consideration, the entity becomes rarer still. It may be contended that without histopathologic evidence, the diagnosis of mandibular melasma should never be made because of its rarity and also because of the fact that the entity itself is mired in controversy. Less than 20 years after Sanchez et al.[2] suggested the morphological classification of melasma, a well-designed clinicopathological study in Puerto Rican women with mandibular melasma concluded that this entity might be entirely different from the other two types of melasma. [3]

Another methodological problem with the study is that depth was solely assessed by Wood's lamp without corroborating the findings histopathologically. In the "Discussion" section, it has been acknowledged, though, that there may not be a correlation between the findings of Wood's lamp examination and the histological depths of pigmentation. A couple of references including one recent Indian clinicopathological study on melasma [4] have been cited in this regard. The authors have attributed the cause to "non-attendance of patients with mild varieties of the disease." [1] I am afraid that this is far too cryptic an explanation to be of any help to the readers. It is to be hoped that the authors have sought to mean that Wood's lamp examination is frequently unreliable except in purely epidermal melasma, particularly in persons with high background pigmentation (i.e. Fitzpatrick's skin types V and VI), who are found in plenty among the Indian population. Sanchez et al., [2] who advocated the assessment of depth of melasma with Wood's lamp in the first place, themselves acknowledged the limitation of this method in patients of dark complexion, in whom the lesions are frequently not discernible. This they hypothesized to be due to the increased number of melanosomes in the normal skin of these individuals. Wood's lamp actually utilizes the physical phenomenon of Tyndall effect (differential scattering), and thus requires a background of relatively low ambient pigmentation (in other words, a fair complexion) so that the contrast between an area of melanotic pigmentation, like that in melasma, and normally pigmented skin may be perceived as an intensification of pigmentation. Thus, in persons with deeper complexion (Fitzpatrick types V and VI), mixed melasma (that is a sizeable subset in any series, including the present one) is frequently inapparent [5] due to lack of contrast on Wood's lamp examination and is liable to be misclassified. However, long back it had been established that regardless of skin type, Wood's lamp examination did not help predict treatment outcome, simply because it did not correlate well enough with histological types, which happen to be the most sensitive prognostic indicators. [6] In fact, currently the only logical use of Wood's lamp in melasma seems to be in the identification of very early and very light patches of melasma in very fair-complexioned patients. Classification of depth in melasma, particularly in patients with darker hues and in the research setting, has to be done either histologically or by novel non-invasive techniques such as in vivo confocal reflectance microscopy. [7]

This article could have been very valuable indeed had these methodological issues been addressed. At the very least, the authors should have clearly acknowledged these limitations in the article.

 
   References Top

1.Achar A, Rathi SK. Melasma: A clinico-epidemiological study of 312 cases. Indian J Dermatol 2011;56:380-2.  Back to cited text no. 1
[PUBMED]  Medknow Journal  
2.Sanchez NP, Pathak MA, Sato S, Fitzpatrick TB, Sanchez JL, Mihm MC Jr. Melasma: A clinical, light microscopic, ultrastructural, and immunofluorescence study. J Am Acad Dermatol 1981;4:698-710.  Back to cited text no. 2
    
3.Mandry Pagán R, Sánchez JL. Mandibular melasma. P R Health Sci J 2000;19:231-4.  Back to cited text no. 3
    
4.Sarvjot V, Sharma S, Mishra S, Singh A. Melasma: A clinicopathological study of 43 cases. Indian J Pathol Microbiol 2009;52:357-9.  Back to cited text no. 4
[PUBMED]  Medknow Journal  
5.Sehgal VN, Verma P, Srivastava G, Aggarwal AK, Verma S. Melasma: Treatment strategy. J Cosmet Laser Ther 2011;13:265-79.  Back to cited text no. 5
    
6.Lawrence N, Cox SE, Brody HJ. Treatment of melasma with Jessner's solution versus glycolic acid: A comparison of clinical efficacy and evaluation of the predictive ability of Wood's light examination. J Am Acad Dermatol 1997;36:589-93.  Back to cited text no. 6
    
7.Ardigo M, Cameli N, Berardesca E, Gonzalez S. Characterization and evaluation of pigment distribution and response to therapy in melasma using in vivo reflectance confocal microscopy: A preliminary study. J Eur Acad Dermatol Venereol 2010;24:1296-303.  Back to cited text no. 7
    



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