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LETTER TO THE EDITOR
Year : 2017  |  Volume : 8  |  Issue : 4  |  Page : 287  

Pachyonychia congenita: Brief appraisal of history and current classification


Department of Dermatology and Venereology, All Institute of Medical Sciences, Rishikesh, Uttarakhand, India

Date of Web Publication5-Jul-2017

Correspondence Address:
Naveen Kumar Kansal
Department of Dermatology and Venereology, All India Institute of Medical Sciences, Rishikesh - 249 201, Uttarakhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/idoj.IDOJ_253_16

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How to cite this article:
Kansal NK. Pachyonychia congenita: Brief appraisal of history and current classification. Indian Dermatol Online J 2017;8:287

How to cite this URL:
Kansal NK. Pachyonychia congenita: Brief appraisal of history and current classification. Indian Dermatol Online J [serial online] 2017 [cited 2020 Aug 15];8:287. Available from: http://www.idoj.in/text.asp?2017/8/4/287/209608

Sir,

We read with great interest the informative case report “Pachyonychia congenita with late onset (PC tarda)” by Sravanthi et al. in the July-August 2016 issue of the Journal.[1] However, we would like to emphasize certain points regarding the history and current classification system of this rare disorder of keratinization [a Mendelian disorder of cornification (MeDOC)].

  1. It is almost universally believed that the disorder was first described by Müller in 1904.[1] However, the first case of PC (with cutaneous horns) was originally described by St George Ash in an Irish girl as early as 1685 (quoted in [2])[3]
  2. A large amount of clinicogenetic information, based on the data collected from the International Pachyonychia Congenita Research Registry (IPCRR), has become available in the last several years. This has formed the basis of a new classification system for PC, gradually replacing earlier classifications, and is based almost exclusively on the mutated genes. This classification was proposed at the 2010 IPC Symposium,[4] and has recently been incorporated in the Rook's Textbook of Dermatology,[5] as well as in several papers.[3],[6] The new classification is as follows:


(a)PC-K6a (caused by mutation of KRT6A); (b) PC-K6b (caused by mutation of KRT6B); (c) PC-K6c (caused by mutation of KRT6C); (d) PC-K16 (caused by mutation of KRT16); and (e) PC-K17 (caused by mutation of KRT17).

To the best of the current author's literature search, many recent Dermatology textbooks do not follow this classification system, as it is a recent one and some pioneers in the field have used the term PC-U, where PC is suspected, but no mutation has either been found (or could not be looked for). PC-U may be used as an “umbrella term” to simplify the classification of PC patients in the 6th type until a genetic testing may help in further classification. It may also be noted that PC-K6c (caused by the mutation of the KRT6C gene) has been least represented (17/535 cases; 3% only).

To conclude, the new classification revealing a broad spectrum of overlapping clinical and pathologic features has closely correlated phenotype to the specific keratin genotype in PC patients.[3],[4] However, limitations of classifying PC patients in India, as per the new classification system, is definitely challenging as diagnostic genetic testing may not be easily available, as was the case in our recent report.[3]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Sravanthi A, Srivalli P, Gopal K, Rao TN. Pachyonychia congenita with late onset (PC tarda). Indian Dermatol Online J 2016;7:278-80.  Back to cited text no. 1
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2.
Leachman SA, Kaspar RL, Fleckman P, Florell SR, Smith FJ, McLean WH, et al. Clinical and pathological features of pachyonychia congenita. J Investig Dermatol Symp Proc 2005;10:3-17.  Back to cited text no. 2
    
3.
Kansal NK, Agarwal S, Joshi U, Choudhary BC, Pant P. Pachyonychia congenita type 1 with cutaneous pseudohorns. Eur J Pediat Dermatol 2015;25:205-8.  Back to cited text no. 3
    
4.
Smith FJD, Hansen CD, Hull PR, Kaspar RL, Schwartz ME, McLean WHI, et al. Pachyonychia congenita. GeneReviews: [Internet]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1280/. [Last updated on 2014 Jul 24; Last cited on 2016 Jul 26].  Back to cited text no. 4
    
5.
Oji V, Metze D, Traupe H. Inherited Disorders of Cornification. In: Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D, editors. Rook's Textbook of Dermatology. 9th ed. Oxford: Wiley-Blackwell; 2016. p. 65.1-65.75.  Back to cited text no. 5
    
6.
Wilson NJ, O'Toole EA, Milstone LM, Hansen CD, Shepherd AA, Al-Asadi E, et al. The molecular genetic analysis of the expanding pachyonychia congenita case collection. Br J Dermatol 2014;171:343-55.  Back to cited text no. 6
    




 

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