Indian Journal of Paediatric Dermatology

: 2017  |  Volume : 18  |  Issue : 1  |  Page : 71--73

Systematized linear porokeratosis: A rare clinical entity

Shouvik Ghosh, Deblina Bhunia, Megha Agarwal, Olympia Rudra, Surajit Kumar Biswas 
 Department of Dermatology, R.G. Kar Medical College, Kolkata, West Bengal, India

Correspondence Address:
Shouvik Ghosh
C-9, Panchasayar P.O., Kolkata - 700 094, West Bengal

How to cite this article:
Ghosh S, Bhunia D, Agarwal M, Rudra O, Biswas SK. Systematized linear porokeratosis: A rare clinical entity.Indian J Paediatr Dermatol 2017;18:71-73

How to cite this URL:
Ghosh S, Bhunia D, Agarwal M, Rudra O, Biswas SK. Systematized linear porokeratosis: A rare clinical entity. Indian J Paediatr Dermatol [serial online] 2017 [cited 2019 Sep 15 ];18:71-73
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Porokeratosis is a disorder of keratinization, clinically presenting as hyperkeratotic papules or plaques with thread-like elevated borders and histopathologically with cornoid lamella.[1] Linear porokeratosis is an uncommon variant of porokeratosis which rarely presents with generalized or systematized distribution. Here, we present a case of generalized linear porokeratosis with extensive involvement and nail dystrophy in a child. A 4-year-old Indian boy, born of a nonconsanguineous marriage, was presented to us by his parents with complaints of skin lesions involving the trunk, upper, and lower extremities. According to the parents, they first noticed small, brownish, elevated lesions over the right forearm when the child was 6-month-old. New lesions gradually appeared to involve the trunk and both the extremities. The child did not receive any treatment for this condition before presenting to us. On examination, we found multiple, hyperpigmented, grouped, hyperkeratotic papules, and annular plaques arranged along Blaschko's lines and distributed over the trunk and upper as well as lower extremities [Figure 1]. The lesions had a predilection for the right side of the body with fewer lesions on the left side. Similar lesions were present over the genitalia. Face, palms, and soles were spared. The lesions extended onto the dorsum of the right hand and digits leading to ridging of the nail of the right index finger. On closer view, each lesion revealed a thin, keratotic, irregular, thread-like elevated margin [Figure 2]. Mucosa and hair examinations were noncontributory. Thorough systemic examination revealed no abnormality. A 4 mm punch biopsy was performed including a margin of the lesion and hematoxylin and eosin staining was done. Histopathological examination revealed hyperkeratosis and the characteristic cornoid lamella - a column of parakeratotic cells in the stratum corneum with the loss of granular cell layer beneath the column [Figure 3]. On the basis of the clinical findings and histopathological examination, the child was diagnosed as a case of systematized linear porokeratosis.{Figure 1}{Figure 2}{Figure 3}

The porokeratoses are a group of disorder of keratinization characterized by hyperkeratotic papules or plaques surrounded by a thread-like elevated border. Several clinical variants of porokeratosis are recognized such as porokeratosis of Mibelli, disseminated superficial actinic porokeratosis, disseminated superficial porokeratosis, porokeratosis palmaris et plantaris disseminata, punctate porokeratosis, and linear porokeratosis. Linear porokeratosis is an uncommon variant that usually presents in early childhood.[1] Presentation at birth has also been reported.[2] Clinically, it is characterized by a linear verrucous eruption that may follow Blaschko's line. Two distinct variants of linear porokeratosis exist. The localized form is more common and usually confined to an extremity. The rare generalized or systematized form presents with multiple lesions involving several extremities as well as the trunk.[1],[3] It may present with unilateral as well as bilateral distribution.[3],[4],[5] Genital involvement [5] and nail dystrophy [3],[5] in linear porokeratosis, as seen in our patient, are extremely rare findings.

The exact etiopathogenesis of porokeratosis is unknown. Porokeratosis is regarded as an autosomal dominant disorder of keratinization. There are genetically determined, abnormal clone of keratinocytes which may become activated by various stimuli, such as sun exposure, viral infection, and immunosuppression.[1],[3] Linear porokeratosis is thought to be a mosaic form of porokeratosis of Mibelli. Although porokeratosis is generally considered to be a chronic disorder with a benign course, linear porokeratosis has the highest potential for malignant transformation. Squamous cell carcinoma is the most common malignancy described in porokeratosis.[1] Porokeratosis is histopathologically characterized by the presence of a column of parakeratotic cells, the cornoid lamella, running through the hyperkeratotic stratum corneum with the loss of granular cell layer below the column.[1],[4] Differential diagnoses of linear porokeratosis include inflammatory linear verrucous epidermal nevus, incontinentia pigmenti (Stage 2), lichen planus, ichthyosis linearis circumflexa, etc.[1] Porokeratosis is differentiated from these diseases clinically by the characteristic margin of the lesion and histopathologically by the cornoid lamella.

Treatment of porokeratosis is usually unnecessary but follow-up is required.[1] Topical therapies include a potent topical steroid, retinoids, Vitamin D3 analog, imiquimod, 5-fluorouracil, etc., Systemic retinoids were found to be effective in generalized cases.[5] The child has been advised topical retinoids and is under regular follow-up.

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2Fisher CA, LeBoit PE, Frieden IJ. Linear porokeratosis presenting as erosions in the newborn period. Pediatr Dermatol 1995;12:318-22.
3Dervis E, Demirkesen C. Generalized linear porokeratosis. Int J Dermatol 2006;45:1077-9.
4Lorenz GE, Ritter SE. Linear porokeratosis: A case report and review of the literature. Cutis 2008;81:479-83.
5Garg T, Ramchander, Varghese B, Barara M, Nangia A. Generalized linear porokeratosis: A rare entity with excellent response to acitretin. Dermatol Online J 2011;17:3.