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Polubothu S, Bender N, Muthiah S, Zecchin D, Demetriou C, Martin SB, Malhotra S, Travnickova J, Zeng Z, Böhm M, Barbarot S, Cottrell C, Davies O, Baselga E, Burrows NP, Carmignac V, Diaz JS, Fink C, Haenssle HA, Happle R, Harland M, Majerowski J, Vabres P, Vincent M, Newton-Bishop JA, Bishop DT, Siegel D, Patton EE, Topf M, Rajan N, Drolet B, Kinsler VA. PTPN11 Mosaicism Causes a Spectrum of Pigmentary and Vascular Neurocutaneous Disorders and Predisposes to Melanoma. J Invest Dermatol 2023; 143:1042-1051.e3. [PMID: 36566878 PMCID: PMC10602917 DOI: 10.1016/j.jid.2022.09.661] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/07/2022] [Accepted: 09/22/2022] [Indexed: 12/24/2022]
Abstract
Phakomatosis pigmentovascularis is a diagnosis that denotes the coexistence of pigmentary and vascular birthmarks of specific types, accompanied by variable multisystem involvement, including CNS disease, asymmetrical growth, and a predisposition to malignancy. Using a tight phenotypic group and high-depth next-generation sequencing of affected tissues, we discover here clonal mosaic variants in gene PTPN11 encoding SHP2 phosphatase as a cause of phakomatosis pigmentovascularis type III or spilorosea. Within an individual, the same variant is found in distinct pigmentary and vascular birthmarks and is undetectable in blood. We go on to show that the same variants can cause either the pigmentary or vascular phenotypes alone, and drive melanoma development within pigmentary lesions. Protein structure modeling highlights that although variants lead to loss of function at the level of the phosphatase domain, resultant conformational changes promote longer ligand binding. In vitro modeling of the missense variants confirms downstream MAPK pathway overactivation and widespread disruption of human endothelial cell angiogenesis. Importantly, patients with PTPN11 mosaicism theoretically risk passing on the variant to their children as the germline RASopathy Noonan syndrome with lentigines. These findings improve our understanding of the pathogenesis and biology of nevus spilus and capillary malformation syndromes, paving the way for better clinical management.
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Affiliation(s)
- Satyamaanasa Polubothu
- Mosaicism and Precision Medicine Laboratory, The Francis Crick Institute, London, United Kingdom; Paediatric Dermatology, Great Ormond Street Hospital, London, United Kingdom; Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Nicole Bender
- Department of Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Siobhan Muthiah
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Davide Zecchin
- Mosaicism and Precision Medicine Laboratory, The Francis Crick Institute, London, United Kingdom; Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Charalambos Demetriou
- Mosaicism and Precision Medicine Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Sara Barberan Martin
- Mosaicism and Precision Medicine Laboratory, The Francis Crick Institute, London, United Kingdom; Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Sony Malhotra
- Scientific Computing Department, Science and Technology Facilities Council, Research Complex at Harwell, Harwell Oxford, United Kingdom
| | - Jana Travnickova
- MRC Human Genetics Unit and Cancer Research UK Edinburgh Centre, MRC Institute of Genetics & Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Zhiqiang Zeng
- MRC Human Genetics Unit and Cancer Research UK Edinburgh Centre, MRC Institute of Genetics & Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Markus Böhm
- Department of Dermatology, University of Münster, Münster, Germany
| | - Sebastien Barbarot
- Department of Dermatology, Centre Hospitalier Universitaire Nantes, Nantes, France
| | - Catherine Cottrell
- Institute for Genomic Medicine, Nationwide Childrens' Hospital, Columbus, USA
| | - Olivia Davies
- Department of Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Eulalia Baselga
- Department of Dermatology, SJD Barcelona Children's Hospital, Barcelona, Spain
| | - Nigel P Burrows
- Department of Dermatology, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Virginie Carmignac
- Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France
| | - Joey Santiago Diaz
- Section of Epidemiology and Biostatistics, Leeds Institute of Cancer and Pathology, Cancer Research UK Clinical Centre at Leeds, St James's University Hospital, Leeds, United Kingdom; Department of Statistics, College of Science, Central Luzon State University, Science City of Munoz, Philippines; Department of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Manila Ermita, Manila, Philippines
| | - Christine Fink
- Department of Dermatology, University of Heidelberg, Heidelberg, Germany
| | - Holger A Haenssle
- Department of Dermatology, University of Heidelberg, Heidelberg, Germany
| | - Rudolf Happle
- Department of Dermatology, Medical Center, University of Freiburg, Freiburg, Germany
| | - Mark Harland
- Section of Epidemiology and Biostatistics, Leeds Institute of Cancer and Pathology, Cancer Research UK Clinical Centre at Leeds, St James's University Hospital, Leeds, United Kingdom
| | - Jacquelyn Majerowski
- Department of Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Pierre Vabres
- Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France; Department of Dermatology, CHU Dijon, Dijon, France
| | - Marie Vincent
- Department of Dermatology, Centre Hospitalier Universitaire Nantes, Nantes, France
| | - Julia A Newton-Bishop
- Division of Haematology and Immunology, Leeds Institute of Medical Research, Leeds, United Kingdom
| | - D Tim Bishop
- Division of Haematology and Immunology, Leeds Institute of Medical Research, Leeds, United Kingdom
| | - Dawn Siegel
- Department of Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - E Elizabeth Patton
- MRC Human Genetics Unit and Cancer Research UK Edinburgh Centre, MRC Institute of Genetics & Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Maya Topf
- Centre for Structural Systems Biology, Leibniz-Institut für Virologie (LIV) and Universitätsklinikum Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Neil Rajan
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Beth Drolet
- Department of Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Veronica A Kinsler
- Mosaicism and Precision Medicine Laboratory, The Francis Crick Institute, London, United Kingdom; Paediatric Dermatology, Great Ormond Street Hospital, London, United Kingdom; Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom.
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Chia SY, Tan EC, Wei H, Zhao Y, Koh MJA. Epidermolytic ichthyosis in a child and systematized epidermolytic nevi in the mosaic parent associated with a KRT1 variant. Eur J Med Genet 2021; 64:104324. [PMID: 34461324 DOI: 10.1016/j.ejmg.2021.104324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 08/16/2021] [Accepted: 08/26/2021] [Indexed: 11/23/2022]
Abstract
Epidermolytic ichthyosis and epidermolytic nevi share the same histopathological features of epidermolytic hyperkeratosis, characterized by distinctive vacuolar degeneration and hypergranulosis of the superficial epidermis. Both are caused by pathogenic variants in either of two keratin genes KRT1or KRT10, with epidermolytic ichthyosis presenting as a generalized phenotype and epidermolytic nevi presenting as a mosaic phenotype. We report a boy who presented as epidermolytic ichthyosis, with diffuse erythema, superficial erosions and flaccid blisters at birth progressing to generalized ichthyosis. He was found to have inherited a novel KRT1 variant from his mother who presented with extensive epidermolytic nevi or mosaic form of epidermolytic ichthyosis, with extensive, linear and Blaschkoid verrucous, hyperkeratotic plaques over the trunk and limbs. This case highlights the importance of recognising post-zygotic mosaicism which might be transmitted to a child, and the different presentations for germline and mosaic carriers.
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Affiliation(s)
- Keshavmurthy A Adya
- Department of Dermatology, Venereology and Leprosy, SBMP Medical College, Hospital and Research Center, BLDE (Deemed to be University), Vijayapur, Karnataka, India
| | - Arun C Inamadar
- Department of Dermatology, Venereology and Leprosy, SBMP Medical College, Hospital and Research Center, BLDE (Deemed to be University), Vijayapur, Karnataka, India
| | - Ajit B Janagond
- Department of Dermatology, Venereology and Leprosy, SBMP Medical College, Hospital and Research Center, BLDE (Deemed to be University), Vijayapur, Karnataka, India
| | - Aparna Palit
- Department of Dermatology and Venereology, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
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Kinsler VA, Boccara O, Fraitag S, Torrelo A, Vabres P, Diociaiuti A. Mosaic abnormalities of the skin: review and guidelines from the European Reference Network for rare skin diseases. Br J Dermatol 2019; 182:552-563. [PMID: 30920652 DOI: 10.1111/bjd.17924] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2019] [Indexed: 12/15/2022]
Abstract
BACKGROUND Cutaneous mosaicism is an area of dermatology in which there has been an explosion of knowledge within the current decade. This has led to fundamental changes in the understanding of the conditions in this field, and to an ongoing paradigm shift in the approach to management of mosaic skin disorders. OBJECTIVES To lay out the general principles of mosaicism as they are currently understood, summarize the known cutaneous mosaic abnormalities of the skin with associated phenotypic and genotypic information, review the latest trials on targeted therapies and propose guidelines for the general approach to a patient with suspected mosaicism. METHODS This was a consensus expert review as part of the European Reference Network project (ERN-Skin). CONCLUSIONS This study provides clinicians with a practical approach to the patient with suspected mosaicism, redefines mosaicism for the modern genetic era, and proposes a new classification system based on genetic mechanism. What's already known about this topic? Cutaneous mosaicism is a complex field of dermatology that encompasses most birthmarks, and many rare syndromes. Some cutaneous patterns are known to be seen in mosaicism. Very few treatment options are available for most mosaic abnormalities of the skin. Recent high-sensitivity genetic techniques have led to an explosion of knowledge about genotype and phenotype in the literature. What does this study add? Expert consensus from the European Reference Network project. Review of knowledge of confirmed mosaic abnormalities of the skin, including cutaneous phenotype, extracutaneous associated features and genotype. Proposed new classification of mosaic abnormalities of the skin by genetic mechanism and therefore inheritance potential. Practical tips on correct sample collection and genetic investigation. Review of trials of targeted therapies. Guidelines for a practical clinical approach to the patient with suspected mosaicism.
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Affiliation(s)
- V A Kinsler
- Paediatric Dermatology, Great Ormond Street Hospital for Children, London, U.K.,Genetics and Genomic Medicine, UCL Institute of Child Health, London, U.K
| | - O Boccara
- Department of Dermatology and Reference Centre for Genodermatoses and Rare Skin Diseases (MAGEC), Université Paris Descartes - Sorbonne Paris Cité, Institut Imagine, Paris, France
| | - S Fraitag
- Department of Pathology, Hôpital Universitaire Necker-Enfants Malades, APHP, Paris, France
| | - A Torrelo
- Department of Dermatology, Hospital Infantil del Niño Jesús, Madrid, Spain
| | - P Vabres
- Department of Dermatology and Reference Centre for Rare Skin Diseases, Dijon University Hospital, Dijon, France.,GAD, Genetics of Anomalies of Development, University of Bourgogne, Dijon, France
| | - A Diociaiuti
- Dermatology Unit, Bambino Gesù Children's Hospital, Rome, Italy
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Happle R. The Molecular Revolution in Cutaneous Biology: Era of Mosaicism. J Invest Dermatol 2017; 137:e73-e77. [PMID: 28411850 DOI: 10.1016/j.jid.2016.03.045] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 02/08/2016] [Accepted: 03/02/2016] [Indexed: 12/14/2022]
Affiliation(s)
- Rudolf Happle
- Department of Dermatology, Freiburg University Medical Center, Freiburg, Germany.
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Eskin-Schwartz M, Drozhdina M, Sarig O, Gat A, Jackman T, Isakov O, Shomron N, Samuelov L, Malchin N, Peled A, Vodo D, Hovnanian A, Ruzicka T, Koshkin S, Harmon RM, Koetsier JL, Green KJ, Paller AS, Sprecher E. Epidermolytic Ichthyosis Sine Epidermolysis. Am J Dermatopathol 2017; 39:440-4. [PMID: 28121638 DOI: 10.1097/DAD.0000000000000674] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Epidermolytic ichthyosis (EI) is a rare disorder of cornification caused by mutations in KRT1 and KRT10, encoding two suprabasal epidermal keratins. Because of the variable clinical features and severity of the disease, histopathology is often required to correctly direct the molecular analysis. EI is characterized by hyperkeratosis and vacuolar degeneration of the upper epidermis, also known as epidermolytic hyperkeratosis, hence the name of the disease. In the current report, the authors describe members of 2 families presenting with clinical features consistent with EI. The patients were shown to carry classical mutations in KRT1 or KRT10, but did not display epidermolytic changes on histology. These observations underscore the need to remain aware of the limitations of pathological features when considering a diagnosis of EI.
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Gach JE, Munro CS, Lane EB, Wilson NJ, Moss C. Two families with Greither's syndrome caused by a keratin 1 mutation. J Am Acad Dermatol 2006; 53:S225-30. [PMID: 16227096 DOI: 10.1016/j.jaad.2005.01.139] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Revised: 01/23/2005] [Accepted: 01/31/2005] [Indexed: 10/25/2022]
Abstract
Transgrediens et progrediens palmoplantar keratoderma, known as Greither's syndrome, was originally described in 1952 and is characterized by diffuse keratoderma of the palms and soles, extending to the back aspects (transgrediens) and involving the skin over the Achilles' tendon. Patchy hyperkeratosis also develops on the shins, knees, elbows, and sometimes on the skin flexures. We describe two unrelated families affected with Greither's syndrome, in which the same dominant missense mutation gave rise to the amino acid change N188S in K1. The previously reported cases of Greither's syndrome showed phenotypic variability suggestive of different underlying gene defects. Our findings suggest that at least some cases of Greither's syndrome are caused by keratin mutations.
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Affiliation(s)
- Joanna E Gach
- Department of Dermatology, Birmingham Children's Hospital, Birmingham, United Kingdom.
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Uezato H, Yamamoto YI, Kuwae C, Nonaka K, Oshiro M, Kariya KI, Nonaka S. A case of bullous congenital ichthyosiform erythroderma (BCIE) caused by a mutation in the 1A helix initiation motif of keratin 1. J Dermatol 2006; 32:801-8. [PMID: 16361731 DOI: 10.1111/j.1346-8138.2005.tb00848.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Accepted: 04/27/2005] [Indexed: 01/14/2023]
Abstract
Bullous congenital ichthyosiform erythroderma (BCIE) is an autosomally dominant inherited disorder characterized by erythematous, erosive, and bullous skin lesions over the entire body at birth and abnormal hyperkeratosis on the palmoplantar sufaces as the patient grows older. BCIE is caused by a mutation in the keratin 1 (K1) and/or keratin 10 (K10) genes, and most pathogenic mutations are found within the helix initiation and termination motifs of the central helical rod domain (K1 and K10) or the upstream H1 homology domain (K10). In addition to inherited cases, sporadic cases due to a new mutation account for approximately half the total cases of BCIE. We report herein a typical sporadic case of BCIE with erythroderma, erosion, and blisters on the entire body surface at birth and palmoplantar and flexuaral areas of hyperkeratosis in the later stage. We found in this case a novel mutation, 559C to T, at amino acid position 187, which resulted in a leucine to phenylalanine substitution within the helix initiation motif of K1.
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Affiliation(s)
- Hiroshi Uezato
- Department of Dermatology, School of Medicine, University of the Ryukyus, Okinawa, Japan
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Abstract
BACKGROUND Nevus comedonicus (NC) is rarely associated with the histopathologic pattern of follicular epidermolytic hyperkeratosis (EHK). We found eight cases reported. In one case, the condition was transmitted to the offspring in the form of generalized EHK. METHODS We describe a case of linear NC with EHK in a 46-year-old woman. RESULTS Histopathologic examination revealed the typical features of NC. Additionally, the follicular epithelial walls showed EHK with characteristic perinuclear vacuolization in the stratum spinosum and stratum granulosum and large, irregular keratohyalin granules in the granular cell layer. CONCLUSIONS The clinical and histopathologic features of this case are consistent with a diagnosis of linear NC with EHK. Lesions of NC suspected by clinical exam should be examined microscopically to look for features of EHK. If present, patients should be educated about the risk, albeit rare, of passing on a more severe form of the disorder to subsequent generations.
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Affiliation(s)
- Amy K Schecter
- Department of Dermatology, Brown Medical School, Providence, RI 02903, USA
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Abstract
Epidermolytic hyperkeratosis is an unusual type of ichthyosis. This inherited keratinization disorder is characterized clinically by erythema, blistering, and peeling shortly after birth. It may resolve and be replaced with thick scaling. It can lead to life-threatening complications, such as sepsis. Histologically, there is a hyperkeratosis and vacuolar degeneration. Genetically, this is an autosomal dominant disease with complete penetrance; however, 50% are spontaneous mutations. The clinical phenotype is a result of alterations in the gene(s) for keratin 1 and/or 10. We review this disorder and its therapy, which is mainly symptomatic with emollients and retinoids.
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Affiliation(s)
- Nicole L Lacz
- Dermatology, UMDNJ-New Jersey Medical School, Newark, New Jersey 07103-2714, USA
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Abstract
Somatic mosaicism for mutations in disease-causing genes has been reported in several recent studies. Examples include hemophilia A, many skin disorders, and several cancers such as retinoblastoma and familial adenomatous polyposis. Many of these disorders require multiple mutations in order to express the disease phenotype. For example, two recessive mutations to the retinoblastoma locus are required to initiate retinoblastomal tumors. I develop a mathematical framework for somatic mosaicism in which two recessive mutations cause disease. With my framework, I analyse the following question: Given an observed frequency of cells with two mutations and an easily scored aberrant phenotype, what is the conditional frequency distribution of cells carrying one mutation and therefore susceptible to transformation by a second mutation? This question is important because a high frequency of carrier cells can cause genetic counselors to misdiagnose a mosaic as an inherited heterozygote carrier and because widespread mosaicism can lead to some germline transmission. As more data accumulate, the observed distribution of mosaics can be compared against my predicted distribution. These sorts of studies will contribute to a broader understanding of the distribution of somatic mutations, a central topic in the study of cancer.
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Affiliation(s)
- Steven A Frank
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697-2525, USA.
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Abstract
Keratins are the type I and II intermediate filament proteins which form a cytoskeletal network within all epithelial cells. They are expressed in pairs in a tissue- and differentiation-specific fashion. Epidermolysis bullosa simplex (EBS) was the first human disorder to be associated with keratin mutations. The abnormal keratin filament aggregates observed in basal cell keratinocytes of some EBS patients are composed of keratins K5 and K14. Dominant mutations in the genes encoding these proteins were shown to disrupt the keratin filament cytoskeleton resulting in cells that are less resilient and blister with mild physical trauma. Identification of mutations in other keratin genes soon followed with attention focussed on disorders showing abnormal clumping of keratin filaments in specific cells. For example, in bullous congenital ichthyosiform erythroderma, clumping of filaments in the suprabasal cells led to the identification of mutations in the suprabasal keratins, K1 and K10. Mutations have now been identified in 18 keratins, all of which produce a fragile cell phenotype. These include ichthyosis bullosa of Siemens (K2e), epidermolytic palmoplantar keratoderma (K1, K9), pachyonychia congenita (K6a, K6b, K16, K17), white sponge nevus (K4, K13), Meesmann's corneal dystrophy (K3, K12), cryptogenic cirrhosis (K8, K18) and monilethrix (hHb6, hHb1).In general, these disorders are inherited as autosomal dominant traits and the mutations act in a dominant-negative manner. Therefore, treatment in the form of gene therapy is difficult, as the mutant gene needs to be inactivated. Ways of achieving this are actively being studied. Reliable mutation detection methods from genomic DNA are now available. This enables rapid screening of patients for keratin mutations. For some of the more severe phenotypes, prenatal diagnosis may be requested and this can now be performed from chorionic villus samples at an early stage of the pregnancy. This review article describes the discovery of, to date, mutations in 18 keratin genes associated with inherited human diseases.
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Affiliation(s)
- Frances Smith
- Epithelial Genetics Group, Human Genetics Unit, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK.
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Leverkus M, Kluwe L, Röll EM, Becker G, Bröcker EB, Mautner VF, Hamm H. Multiple unilateral schwannomas: segmental neurofibromatosis type 2 or schwannomatosis? Br J Dermatol 2003; 148:804-9. [PMID: 12752143 DOI: 10.1046/j.1365-2133.2003.05249.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Schwannomas are benign solitary tumours of the peripheral nerve sheaths. The occurrence of multiple schwannomas usually implies hereditary disease. The most frequent syndrome associated with multiple schwannomas is neurofibromatosis type 2 (NF2), which is defined by bilateral vestibular schwannomas. Schwannomatosis is a distinct disease characterized by multiple pathologically proven schwannomas in the absence of vestibular schwannomas. It is not currently known if the presence of multiple schwannomas confined to a limb may represent a mosaic form of NF2 or a distinct disease, because mutation analysis of these tumours is not routinely performed. We report a 31-year-old patient who presented with multiple slowly growing subcutaneous tumours on his left arm. His family history was negative for cutaneous tumours or central nervous system disease, and he did not have additional features of NF2. Magnetic resonance tomography and ophthalmological examination excluded vestibular schwannoma and eye stigmata of NF2. After resection of three tumours, histological analysis confirmed the diagnosis of benign schwannomas. Molecular genetic analysis by temperature gradient gel electrophoresis and microsatellite marker analysis demonstrated two distinct mutations of the NF2 gene (NF2) in two different schwannomas, with concomitant loss of heterozygosity in both tumours. In contrast, neither normal skin nor peripheral blood lymphocytes revealed mutations of NF2. The clinical and molecular genetic findings suggest that the diagnosis in our patient is schwannomatosis rather than segmental NF2 because the mutations found in different tumours were not identical. The possibility of a localized predisposition for the acquisition of NF2 mutations is discussed.
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Affiliation(s)
- M Leverkus
- Department of Dermatology, University of Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany.
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Affiliation(s)
- Amy S Paller
- Division of Dermatology, Children's Memorial Hospital, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60614, USA.
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Terron-Kwiatkowski A, Paller AS, Compton J, Atherton DJ, McLean WHI, Irvine AD. Two cases of primarily palmoplantar keratoderma associated with novel mutations in keratin 1. J Invest Dermatol 2002; 119:966-71. [PMID: 12406346 DOI: 10.1046/j.1523-1747.2002.00186.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutations in keratin 1 were initially described in the classical form of bullous congenital ichthyosiform erythroderma (also known as epidermolytic hyperkeratosis). More recently the range of phenotypes associated with mutations in this gene has been extended to include annular ichthyosiform erythroderma and mild epidermolytic palmoplantar keratoderma. Here we present two novel mutations in the keratin 1 gene (KRT1): a 5' donor splice site mutation in exon 1 (591 + 2T > A) that predicts a 22 amino acid in-frame deletion in the keratin 1 1A domain; and an in-frame deletion in exon 7 (1376del24) that predicts a foreshortened 2B coiled-coil domain of keratin 1. In each case these mutations are associated with palmoplantar keratoderma and mild ichthyosis, largely limited to the flexural areas. These mutations appear to have a less damaging effect than previously reported mis-sense mutations sited in the helix boundary motifs. This report extends the range of phenotypes associated with mutations in KRT1.
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Affiliation(s)
- Ana Terron-Kwiatkowski
- Human Genetics Unit, University of Dundee, Ninewells Hospital & Medical School, Dundee, U.K
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17
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Abstract
Somatic mosaicism -- the presence of genetically distinct populations of somatic cells in a given organism -- is frequently masked, but it can also result in major phenotypic changes and reveal the expression of otherwise lethal genetic mutations. Mosaicism can be caused by DNA mutations, epigenetic alterations of DNA, chromosomal abnormalities and the spontaneous reversion of inherited mutations. In this review, we discuss the human disorders that result from somatic mosaicism, as well as the molecular genetic mechanisms by which they arise. Specifically, we emphasize the role of selection in the phenotypic manifestations of mosaicism.
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Affiliation(s)
- Hagop Youssoufian
- Department of Clinical Discovery, Bristol-Myers Squibb Company, Princeton, New Jersey 08543-4000, USA.
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Cuevas-Covarrubias SA, Jiménez-Vaca AL, González-Huerta LM, Valdes-Flores M, Del Refugio Rivera-Vega M, Maya-Nunez G, Kofman-Alfaro SH. Somatic and germinal mosaicism for the steroid sulfatase gene deletion in a steroid sulfatase deficiency carrier. J Invest Dermatol 2002; 119:972-5. [PMID: 12406347 DOI: 10.1046/j.1523-1747.2002.t01-1-00185.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Steroid sulfatase deficiency results in X-linked ichthyosis, an inborn error of metabolism in which the principal molecular defect is the complete deletion of the steroid sulfatase gene and flanking markers. Mosaicism for the steroid sulfatase gene has not yet been reported in X-linked ichthyosis. In this study we describe an X-linked ichthyosis patient with complete deletion of the steroid sulfatase gene and his mother with somatic and germinal mosaicism for this molecular defect. The family (X-linked ichthyosis patient, grandmother, mother, and sister) was analyzed through steroid sulfatase enzyme assay, polymerase chain reaction, DNA markers, and fluorescence in situ hybridization of the steroid sulfatase gene. Steroid sulfatase activity was undetectable in the X-linked ichthyosis patient, very low in the mother, and normal in the grandmother and sister. The X-linked ichthyosis patient showed a 2 Mb deletion of the steroid sulfatase gene and flanking regions from 5'DXS1139 to 3'DXF22S1. The mother showed one copy of the steroid sulfatase gene in 98.5% of oral cells and in 80% of leukocytes. The grandmother and sister showed two copies of the steroid sulfatase gene. The origin of the X chromosome with the deletion of the steroid sulfatase gene corresponded to the grandfather of the proband. We report the first case of somatic and germinal mosaicism of the steroid sulfatase gene in an X-linked ichthyosis carrier and propose DNA slippage as the most plausible mechanism in the genesis of this mosaicism.
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