What are the less common forms of porokeratosis?

Updated: Oct 09, 2020
  • Author: Amarateedha Prak LeCourt, MD; Chief Editor: William D James, MD  more...
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Less commonly reported clinical entities that share the histopathologic characteristic of cornoid lamellation include the following:

  • Porokeratosis ptychotropica, a verrucous variant localized to the buttocks [4]
  • Porokeratoma, also referred to as porokeratotic acanthoma, an entity arising as a solitary keratotic or verrucous nodule with prominent multiple and confluent cornoid lamellae [5]
  • Porokeratotic adnexal ostial nevus (PAON), a rare congenital disorder of keratinization with eccrine and hair follicle involvement: This name was proposed to incorporate porokeratotic eccrine ostial and dermal duct nevus (PEODDN) and porokeratotic eccrine and hair follicle nevus (PEHFN). [6]
  • Pruritic papular porokeratosis, in which intensely pruritic papules and plaques arise fairly abruptly in a patient with or without preexisting DSP [7, 8]
  • Pigmented porokeratosis: A case published in 2016 showed a new possible variant of porokeratosis. Biopsies showed prominent melanocytic hyperplasia in 8 of 31 patients studied. The case represents a distinct variant of porokeratosis; biopsies were performed to clinically exclude melanoma. An erroneous diagnosis of melanoma in situ can be avoided with increased recognition of this entity. [9]
  • Punctate follicular porokeratosis: This has been described in two separate reports, which supports the contention that this is a unique form rather than just a variation in histology. In both cases, the cornoid lamellae originated exclusively from hair follicles with no associated annular plaque. Diagnosis relies heavily on proper histopathologic sampling, and the rarity of this variant could be explained by the low prevalence of this condition in the population or perhaps low biopsy rate of lesions that appear to represent a localized form of keratosis pilaris to physicians. [10]

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