Porokeratosis



Porokeratosis


George R. Collins, DO

Joseph Susa, DO

Clay J. Cockerell, MD










Disseminated superficial actinic porokeratosis presents here as multiple, small, well-demarcated, erythematous, annular plaques image with raised hyperkeratotic peripheral ridges (cornoid lamellae).






Porokeratosis of Mibelli demonstrates a sharply demarcated oval plaque with an erythematous center surrounded by a raised, hyperkeratotic, peripheral ridge that represents the cornoid lamella image.


TERMINOLOGY


Abbreviations



  • Disseminated superficial actinic porokeratosis (DSAP), disseminated superficial porokeratosis (DSP), porokeratosis palmaris et plantaris disseminata (PPPD), punctate porokeratosis (PP), linear porokeratosis (LP)


Synonyms



  • Inclusive term “porokeratosis” may be used to refer to any or all of the various distinct clinical variants of porokeratosis


Definitions



  • Genodermatosis with clonal keratinocytic proliferation resulting in a clinically and morphologically distinct keratinization disorder



    • Hyperkeratotic plaques or papules surrounded by centrifugally expansile, thread-like, raised border that results in characteristic cornoid lamella


  • Several clinical variants of porokeratosis with overlapping features exist among described varieties



    • Classic variant: Porokeratosis of Mibelli


    • Common disseminated variants: Disseminated superficial actinic porokeratosis and disseminated superficial porokeratosis


    • Rare variants: Porokeratosis palmaris et plantaris disseminata, linear porokeratosis, localized porokeratosis, punctate porokeratosis, CAP syndrome, reticulate form, and many others


ETIOLOGY/PATHOGENESIS


Developmental Anomaly



  • Genetically heterogeneous condition that may be familial and tends to be inherited in autosomal dominant manner


  • Fully penetrant by 4th decade of life


  • Pathogenetic mechanisms are still somewhat unclear


  • Multiple current proposed concepts of pathogenetic mechanisms



    • Loci at chromosome bands 12q23.2-24.1 and 15q25.1-26 (DSAP1 and DSAP2) described in familial disseminated superficial actinic porokeratoses



      • Locus at DSAP1 corresponds to SART3, a candidate gene encoding a tumor rejection antigen and felt to be involved in regulation of mRNA splicing


      • SART3 mutations may thus result in altered proliferation and transformation of epithelial cells


    • Locus identified for disseminated superficial porokeratosis (DSP) at 18p11.3


    • Centrifugal expansion of cornoid lamellae in lesions may reflect migration of mutant clone of keratinocytes based on DNA ploidy and chromosome abnormalities


    • Higher prevalence of porokeratosis in immunosuppressed patients suggests impaired immunity, which permits disease in genetically predisposed


  • CAP syndrome (craniosynostosis, anal anomalies, and porokeratosis) is a rare genodermatosis found in only a few ethnically diverse families so far



    • Main phenotypic features are craniosynostosis and clavicular hypoplasia, anal anomalies, and widespread, small porokeratotic papules affecting face and extremities starting at 1 month of age


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Relatively common pathological process



      • Disseminated superficial actinic porokeratosis is most common clinical variant


  • Age



    • Classic porokeratosis of Mibelli and rare linear porokeratosis variant begin during infancy or childhood with expansion of lesions in adulthood



    • DSAP and DSP variants often develop during 3rd or 4th decade of life


    • Porokeratosis palmaris et plantaris disseminata and punctate porokeratosis variants appear during adolescence and early adulthood


  • Gender



    • Porokeratosis of Mibelli and porokeratosis palmaris et plantaris disseminata show male predilection


    • DSAP and DSP both show female predilection: F:M = 3:1


Site



  • Distribution and site of lesions varies depending on clinical variant of porokeratosis



    • Porokeratosis of Mibelli develops as one or more round to oval plaques unilaterally on extremities


    • DSAP is typically widely distributed symmetrically over sun-exposed areas of extremities, with rare facial involvement and usual sparing of palms, soles, and mucous membranes


    • DSP occurs symmetrically on extremities similar to DSAP, but sun-protected areas are not spared


Presentation

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Porokeratosis
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