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Linear systematized porokeratosis—A rare case and dermoscopic clues to diagnosis
Manoj K Nayak1, Aditi Dhanta1, Neirita Hazarika1, Arvind Kumar2
1 Department of Dermatology, Venereology and Leprosy, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
2 Department of Pathology, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| Date of Submission | 26-May-2020 |
| Date of Decision | 22-Jun-2020 |
| Date of Acceptance | 17-Jul-2020 |
| Date of Web Publication | 19-Sep-2020 |
Correspondence Address:
Aditi Dhanta,
Department of Dermatology, Venereology and Leprosy, All India Institute of Medical Sciences, Rishikesh - 249 203, Uttrakhand
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/idoj.IDOJ_419_20
How to cite this URL:
Nayak MK, Dhanta A, Hazarika N, Kumar A. Linear systematized porokeratosis—A rare case and dermoscopic clues to diagnosis. Indian Dermatol Online J [Epub ahead of print] [cited 2020 Nov 1]. Available from: https://www.idoj.in/preprintarticle.asp?id=295458 |
Porokeratosis is a rare autosomal dominant keratinization disorder characterized clinically by well-defined scaly papules and plaques with hyperkeratotic ridges at the margin, and histopathologically by coronoid lamellae.[1] Linear subtype of porokeratosis normally presenting in a Blaschko-linear distribution can be confused clinically with many Blaschko-linear dermatoses.
A 43-year-old male presented with complaints of hyperpigmented papules which started over the distal aspect of upper and lower limb of left side around the age of 8 years. The papules spread centrifugally in a Blaschkoid pattern over a period of 15 years to involve the left side of the body without crossing the midline. On cutaneous examination there were multiple well-defined skin colored to hyperpigmented annular plaques of size varying from 0.5 × 0.5 cm to 2 × 2 cm, with central atrophy and peripheral raised thready hyperpigmented border with a collarette of whitish scales present unilaterally along the Blaschko lines on left upper limb, lower limb, neck and part of the trunk [Figure 1]a, [Figure 1]b, [Figure 1]c. Systemic examination and laboratory investigations did not reveal any abnormalities. Clinically differential diagnosis of Blaschkoid lichen planus and linear porokeratosis were considered. | Figure 1: (a and b):Multiple well defined hyperpigmented annular plaques of size varying from 0.5 * 0.5 cm to 3*3 cm with minimal central atrophy and peripheral raised thready hyperpigmented border with a collarette of whitish scales extending unilaterally along the lines of Blaschko from left side of neck to upper limb. (c) Multiple well defined hyperpigmented annular plaques of size varying from 0.5 * 0.5 cm to 3*3 cm with peripheral raised thready hyperpigmented border with a collarette of whitish scales extending unilaterally along the lines of Blaschko in left lower limb
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Dermoscopy of the periphery of lesion (DermLite II hybrid m; 3 Gen; polarized mode, ×10 magnification) showed a greyish white track made by a collarette of scale with two free edges, broken at places, with a hyperpigmented blackish rim medial to it over a brown background [Figure 2]a. One of the lesion showed a perifollicular cast and exaggerated pigment network with grey globules [Figure 2]b. A 4-mm punch biopsy taken for histopathological evaluation from the thready border of the lesion revealed coronoid lamellae with few dyskeratotic cells, focally absent granular layer and dermal inflammatory infiltrate just below the coronoid lamellae [Figure 3]a and [Figure 3]b. These features thus confirmed the diagnosis of linear systematized porokeratosis. The patient was started on tretinoin 0.05% cream once daily with no improvement on follow-up after 1 month. | Figure 2: (a) Dermoscopy of the periphery of lesion using DermLite II hybrid m; 3Gen; polarized mode, ×10 magnification showed a track made by a collarette of scale (black arrow) with two free edges broken at some places over a brown background. (b) Dermoscopy using DermLite II hybrid m; 3Gen; polarized mode, ×10 magnification showed hyperpigmented blackish rim inner to track made of collarette of scale (black circle), and a perifollicular cast (black arrow) near the centre
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 | Figure 3: (a) Photomicrograph showing focal coornoid lamellae with agranulosis with corresponding papillary dermis showing moderate lymphohistiocytic infiltrate. (H &E; 10×). (b) Photomicrograph showing coronoid lamellae with few dyskeratotic cells and focally absent stratum granulosum (H & E; 40×)
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Linear porokeratosis is an uncommon variant of porokeratosis which normally presents in infancy or childhood as hyperkeratotic flat papules arranged in a Blaschko-linear pattern.[1] It is thought to be a manifestation of post-zygotic mosaicism and carries the highest risk for malignant degeneration.[1] Linear porokeratosis can be further categorized into localized, zosteriform, systematized and generalized.[1],[2] Localized form is unilateral, confined to an extremity and usually distal.[2] Systematized linear porokeratosis is a disseminated variant which may be unilateral or bilateral to become a generalized form.[1] Differential diagnoses for Blaschkoid distribution of lesions includes linear psoriasis, linear lichen planus, linear Darier's disease, and inflammatory linear verrucous nevus.
Diagnosis of porokeratosis is confirmed by its characteristic histopathological feature of coronoid lamella consisting of a column of parakeratotic corneocytes in association with focal absence of stratum granulosum.[1] The dermoscopic findings of linear porokeratosis and its differential diagnoses are summarized in [Table 1].[3],[4],[5] | Table 1: Dermoscopic features of porokeratosis and its differential diagnosis
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This rare entity should always be considered in cases of Blaschko-linear dermatoses due to its risk of malignancy. Dermoscopy can be a useful auxiliary non-invasive tool in diagnosing this entity alleviating the need for biopsy.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
 References | |  |
| 1. | French LE. Rook's Textbook of Dermatology. 9 th ed. Christopher Griffiths, JonathanBarker, Tanya Bleiker, Robert Chalmers, Daniel Creamer, editors. Br J Dermatol 2017;176:1675-6.  |
| 2. | Dervis E, Demirkesen C. Generalized linear porokeratosis. Int J Dermatol 2006;45:1077-9. |
| 3. | Errichetti E, Francesco V De, Pegolo E, Stinco G. Dermoscopy in assisting the diagnosis of linear porokeratosis. J Dermatol 2017;44:248-9. |
| 4. | Errichetti E. Dermoscopy of Inflammatory dermatoses (Inflammoscopy): An up-to-date overview. Dermatol Pract Concept 2019;9:169-80. |
| 5. | Kim DW, Kwak H Bin, Yun SK, Kim HU, Park J. Dermoscopy of linear dermatosis along Blaschko's line in childhood: Lichen striatus versus inflammatory linearverrucous epidermal nevus. J Dermatol 2017;44:355-6. |
[Figure 1], [Figure 2], [Figure 3]
[Table 1]
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