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Keratotic Plaques on the Left Trunk Area and All Extremities—Diagnosis

Keratotic Plaques on the Left Trunk Area and All Extremities—Diagnosis Diagnosis: Porokeratosis, with clinical manifestations typical of both linear porokeratosis (LP) and disseminated superficial actinic porokeratosis (DSAP). Microscopic findings Histopathologic examination of a representative lesion from the left trunk area revealed an atrophic epidermis in the central area, while the hyperkeratotic border was characterized by a column of tightly packed parakeratotic cells, signifying a cornoid lamella. A discrete lymphocytic infiltrate was present in the papillary dermis. A biopsy specimen from a papule on the left lower leg area showed an identical picture (not shown). Discussion Porokeratoses can present as distinct clinical variants, including classic porokeratosis of Mibelli, DSAP, LP, porokeratosis punctata palmaris et plantaris, and porokeratosis plantaris palmaris et disseminata.1 In all types, the lesions are characterized by a hyperkeratotic rim that histologically corresponds to the cornoid lamella. Porokeratoses are inherited as an autosomal dominant trait. The loci responsible for DSAP have been mapped to chromosomes 12q, 15q, and 18q.2-4 Recently, several mutations have been identified in the SSH1 gene on chromosome 12, which encodes a phosphatase that plays a pivotal role in actin dynamics.5 Rarely, concurrence of different variants of porokeratoses has been observed.6 In these cases, clinical morphological features that were typical of both LP and DSAP were seen in the same patient; the LP lesions followed the lines of Blaschko and had a rather severe phenotype, while the lesions more typical of DSAP showed relatively mild changes. Happle7 introduced the concept of type 2 segmental mosaicism, which may explain the concurrence of diffuse disease with patterns of exacerbation that follow the lines of Blaschko. According to his hypothesis, a postzygotic mutational event leads to loss of the wild-type allele in a heterozygous embryo (loss of heterozygosity) at an early stage of embryogenesis. As a consequence, cells originating from the clone affected by loss of heterozygosity proliferate, distribute in a pattern following the lines of Blaschko, and present with a severe phenotype of the respective disease, while the remaining skin consisting of heterozygous cells shows a milder manifestation. The concept of type 2 segmental mosaicism was recently confirmed at a molecular level for Hailey-Hailey disease.8 The pathogenesis of porokeratosis is not yet clear. It has been assumed that a clone of abnormal cells gives rise to the cornoid lamella.9 Other authors suggest that an autoimmune reaction against the clone of abnormal keratinocytes promotes proliferation of epidermal cells and formation of the cornoid lamella.10 Treatment modalities reported for porokeratosis include topical and systemic retinoids, topical fluorouracil, topical imiquimod, cryotherapy, shave excision, and curettage.11 Dermabrasion and carbon dioxide laser vaporization may be a therapeutic option, especially for patients with LP. To our knowledge, however, controlled trials and data on long-term follow-up are not currently available. References 1. Schamroth JMZlotogorski AGilead L Porokeratosis of Mibelli: overview and review of the literature. Acta Derm Venereol 1997;77207- 213Google Scholar 2. Xia JHYang YFDeng H et al. Identification of a locus for disseminated superficial actinic porokeratosis at chromosome 12q23.2-24.1. J Invest Dermatol 2000;1141071- 1074Google ScholarCrossref 3. Xia KDeng HXia JH et al. A novel locus (DSAP2) for disseminated superficial actinic porokeratosis maps to chromosome 15q25.1-26.1. Br J Dermatol 2002;147650- 654Google ScholarCrossref 4. Freyschmidt-Paul PHoffmann RKönig AHapple R Linear porokeratosis superimposed on disseminated superficial actinic porokeratosis: report of two cases exemplifying the concept of type 2 segmental manifestation of autosomal dominant skin disorders. J Am Acad Dermatol 1999;41644- 647Google ScholarCrossref 5. Wei SYang SLin D et al. A novel locus for disseminated superficial porokeratosis maps to chromosome 18p11.3. J Invest Dermatol 2004;123872- 875Google ScholarCrossref 6. Zhang ZNiu ZYuan W et al. Fine mapping and identification of a candidate gene SSH1 in disseminated superficial actinic porokeratosis. Hum Mutat 2004;24438Google ScholarCrossref 7. Happle R A rule concerning the segmental manifestation of autosomal dominant skin disorders: review of clinical examples providing evidence for dichotomous types of severity. Arch Dermatol 1997;1331505- 1509Google ScholarCrossref 8. Poblete-Gutiérrez PWiederholt TKönig A et al. Allelic loss underlies type 2 segmental Hailey-Hailey disease, providing molecular confirmation of a novel genetic concept. J Clin Invest 2004;1141467- 1474Google Scholar 9. Reed RJLeone P Porokeratosis: a mutant clonal keratosis of the epidermis. Arch Dermatol 1970;101340- 347Google ScholarCrossref 10. Shumack SCommens CKossard S Disseminated superficial actinic porokeratosis: a histological review of 61 cases with particular reference to lymphocytic inflammation. Am J Dermatopathol 1991;1326- 31Google ScholarCrossref 11. Pierson DBandel CEhrig TCockerell CJ Benign epidermal tumors and proliferations. Bologna JLJorizzo JLRapini PReds. Dermatology St Louis, Mo Mosby–Year Book Inc2003;1697- 1720Google Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Dermatology American Medical Association

Keratotic Plaques on the Left Trunk Area and All Extremities—Diagnosis

Archives of Dermatology , Volume 142 (8) – Aug 1, 2006
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Keratotic Plaques on the Left Trunk Area and All Extremities—Diagnosis

Abstract

Diagnosis: Porokeratosis, with clinical manifestations typical of both linear porokeratosis (LP) and disseminated superficial actinic porokeratosis (DSAP). Microscopic findings Histopathologic examination of a representative lesion from the left trunk area revealed an atrophic epidermis in the central area, while the hyperkeratotic border was characterized by a column of tightly packed parakeratotic cells, signifying a cornoid lamella. A discrete lymphocytic infiltrate was present in the...
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References (11)

Publisher
American Medical Association
Copyright
Copyright © 2006 American Medical Association. All Rights Reserved.
ISSN
0003-987X
eISSN
1538-3652
DOI
10.1001/archderm.142.8.1059-g
Publisher site
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Abstract

Diagnosis: Porokeratosis, with clinical manifestations typical of both linear porokeratosis (LP) and disseminated superficial actinic porokeratosis (DSAP). Microscopic findings Histopathologic examination of a representative lesion from the left trunk area revealed an atrophic epidermis in the central area, while the hyperkeratotic border was characterized by a column of tightly packed parakeratotic cells, signifying a cornoid lamella. A discrete lymphocytic infiltrate was present in the papillary dermis. A biopsy specimen from a papule on the left lower leg area showed an identical picture (not shown). Discussion Porokeratoses can present as distinct clinical variants, including classic porokeratosis of Mibelli, DSAP, LP, porokeratosis punctata palmaris et plantaris, and porokeratosis plantaris palmaris et disseminata.1 In all types, the lesions are characterized by a hyperkeratotic rim that histologically corresponds to the cornoid lamella. Porokeratoses are inherited as an autosomal dominant trait. The loci responsible for DSAP have been mapped to chromosomes 12q, 15q, and 18q.2-4 Recently, several mutations have been identified in the SSH1 gene on chromosome 12, which encodes a phosphatase that plays a pivotal role in actin dynamics.5 Rarely, concurrence of different variants of porokeratoses has been observed.6 In these cases, clinical morphological features that were typical of both LP and DSAP were seen in the same patient; the LP lesions followed the lines of Blaschko and had a rather severe phenotype, while the lesions more typical of DSAP showed relatively mild changes. Happle7 introduced the concept of type 2 segmental mosaicism, which may explain the concurrence of diffuse disease with patterns of exacerbation that follow the lines of Blaschko. According to his hypothesis, a postzygotic mutational event leads to loss of the wild-type allele in a heterozygous embryo (loss of heterozygosity) at an early stage of embryogenesis. As a consequence, cells originating from the clone affected by loss of heterozygosity proliferate, distribute in a pattern following the lines of Blaschko, and present with a severe phenotype of the respective disease, while the remaining skin consisting of heterozygous cells shows a milder manifestation. The concept of type 2 segmental mosaicism was recently confirmed at a molecular level for Hailey-Hailey disease.8 The pathogenesis of porokeratosis is not yet clear. It has been assumed that a clone of abnormal cells gives rise to the cornoid lamella.9 Other authors suggest that an autoimmune reaction against the clone of abnormal keratinocytes promotes proliferation of epidermal cells and formation of the cornoid lamella.10 Treatment modalities reported for porokeratosis include topical and systemic retinoids, topical fluorouracil, topical imiquimod, cryotherapy, shave excision, and curettage.11 Dermabrasion and carbon dioxide laser vaporization may be a therapeutic option, especially for patients with LP. To our knowledge, however, controlled trials and data on long-term follow-up are not currently available. References 1. Schamroth JMZlotogorski AGilead L Porokeratosis of Mibelli: overview and review of the literature. Acta Derm Venereol 1997;77207- 213Google Scholar 2. Xia JHYang YFDeng H et al. Identification of a locus for disseminated superficial actinic porokeratosis at chromosome 12q23.2-24.1. J Invest Dermatol 2000;1141071- 1074Google ScholarCrossref 3. Xia KDeng HXia JH et al. A novel locus (DSAP2) for disseminated superficial actinic porokeratosis maps to chromosome 15q25.1-26.1. Br J Dermatol 2002;147650- 654Google ScholarCrossref 4. Freyschmidt-Paul PHoffmann RKönig AHapple R Linear porokeratosis superimposed on disseminated superficial actinic porokeratosis: report of two cases exemplifying the concept of type 2 segmental manifestation of autosomal dominant skin disorders. J Am Acad Dermatol 1999;41644- 647Google ScholarCrossref 5. Wei SYang SLin D et al. A novel locus for disseminated superficial porokeratosis maps to chromosome 18p11.3. J Invest Dermatol 2004;123872- 875Google ScholarCrossref 6. Zhang ZNiu ZYuan W et al. Fine mapping and identification of a candidate gene SSH1 in disseminated superficial actinic porokeratosis. Hum Mutat 2004;24438Google ScholarCrossref 7. Happle R A rule concerning the segmental manifestation of autosomal dominant skin disorders: review of clinical examples providing evidence for dichotomous types of severity. Arch Dermatol 1997;1331505- 1509Google ScholarCrossref 8. Poblete-Gutiérrez PWiederholt TKönig A et al. Allelic loss underlies type 2 segmental Hailey-Hailey disease, providing molecular confirmation of a novel genetic concept. J Clin Invest 2004;1141467- 1474Google Scholar 9. Reed RJLeone P Porokeratosis: a mutant clonal keratosis of the epidermis. Arch Dermatol 1970;101340- 347Google ScholarCrossref 10. Shumack SCommens CKossard S Disseminated superficial actinic porokeratosis: a histological review of 61 cases with particular reference to lymphocytic inflammation. Am J Dermatopathol 1991;1326- 31Google ScholarCrossref 11. Pierson DBandel CEhrig TCockerell CJ Benign epidermal tumors and proliferations. Bologna JLJorizzo JLRapini PReds. Dermatology St Louis, Mo Mosby–Year Book Inc2003;1697- 1720Google Scholar

Journal

Archives of Dermatology – American Medical Association

Published: Aug 1, 2006

Keywords: limb,keratosis,trunk structure

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