Resident Rounds: Part III
Generalized Linear Porokeratosis

June 2012 | Volume 11 | Issue 6 | Features | 772 | Copyright © June 2012



A Caucasian female, aged 3 years, presented to our clinic for evaluation of asymptomatic, slowly enlarging pink and brown scaly plaques on her trunk and extremities, which had been present since birth. Past medical history was significant for environmental allergies and recurrent otitis media necessitating myringotomy tubes. Active medication list included loratadine and montelukast sodium. There was no family history of similar skin lesions.
Upon initial evaluation, the patient was found to have several irregular, 5 mm to 4 cm, atrophic, hyperpigmented thin plaques with well-defined borders on the right and left upper arms, lower legs, left chest, and vulva following a blashkoid distribution (Figures 1 and 2). There was sparing of the palms and soles. Pathology showed mild papillomatosis and hyperkeratosis associated with tiers of parakeratosis extending above foci of a thinned granular layer and epidermal dysmaturation (Figure 3). Based on the clinical and pathologic findings, a diagnosis of generalized linear porokeratosis was rendered.


Linear porokeratosis was first described by Mibelli in 1893, and then later characterized as a distinct subset of porokeratosis of Mibelli in 1974.1 The pathogenesis of porokeratosis is not known. One theory is that porokeratoses arise from a rapidly spreading clone of epidermal cells, which creates a fold or groove at the point of contact with normal keratinocytes. This border is histologically manifested by a coronoid lamella. 2 Somatic recombination may provide a mechanism for the development of epidermal clones.3 Most types of porokeratosis, including disseminated superficial actinic porokeratosis, porokeratosis of Mibelli, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis have an autosomal dominant inheritance pattern. Congenital porokeratosis likely results from genetic mosaicism.4
Numerous modalities have been used to treat porokeratoses with varying success. These include topical 5-fluorouracil, topical imiquimod, topical and oral retinoids, photodynamic
table 1
therapy, surgical excision and destruction, and carbon dioxide laser therapy. For our patient, treatment with tretinoin 0.025% cream was initiated to one area of involvement. She has yet to follow up in our clinic.