115. Principles of Genetics, Mosaicism and Molecular Biology

  1. Alan D. Irvine MD, FRCPI, FRCP2,3,
  2. Peter H. Hoeger MD4,5 and
  3. Albert C. Yan MD, FAAP, FAAD6,7
  1. Rudolf Happle

Published Online: 24 MAY 2011

DOI: 10.1002/9781444345384.ch115

Harper's Textbook of Pediatric Dermatology, Volume 1, 2, Third Edition

Harper's Textbook of Pediatric Dermatology, Volume 1, 2, Third Edition

How to Cite

Happle, R. (2011) Principles of Genetics, Mosaicism and Molecular Biology, in Harper's Textbook of Pediatric Dermatology, Volume 1, 2, Third Edition (eds A. D. Irvine, P. H. Hoeger and A. C. Yan), Wiley-Blackwell, Oxford, UK. doi: 10.1002/9781444345384.ch115

Editor Information

  1. 2

    Trinity College, Dublin, Ireland

  2. 3

    Our Lady's Children's Hospital, Dublin, Ireland

  3. 4

    University of Hamburg, Hamburg, Germany

  4. 5

    Catholic Children's Hospital Wilhelmstift, Hamburg, Germany

  5. 6

    University of Pennsylvania School of Medicine, Philadelphia, PA, USA

  6. 7

    The Children's Hospital of Philadelphia, Philadelphia, PA, USA

Author Information

  1. Department of Dermatology, Philipp University of Marburg, Marburg, Germany

Publication History

  1. Published Online: 24 MAY 2011
  2. Published Print: 3 JUN 2011

ISBN Information

Print ISBN: 9781405176958

Online ISBN: 9781444345384

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Keywords:

  • compound heterozygosity;
  • didymosis;
  • epigenetic inheritance;
  • loss of heterozygosity;
  • paradominant transmission;
  • patterns of cutaneous mosaicism;
  • revertant mosaicism;
  • superimposed segmental manifestation of polygenic skin disorders;
  • type 2 segmental manifestation of autosomal dominant skin disorders;
  • uniparental disomy

Summary

Today, exceptions and variations on the theme of Mendelian inheritance include genomic imprinting, anticipation, uniparental disomy, compound heterozygosity, semi-dominant inheritance, pseudo-dominance, paradominance, gonadal mosaicism, hypomorphic alleles and epigenetic inheritance. Archetypic patterns of mosaicism are Blaschko's lines (e. g. incontinentia pigmenti), chequerboard pattern (naevi spili), phylloid pattern (phylloid hypomelanosis), the patchy pattern without midline separation (giant melanoctic naevi) and the lateralization pattern (CHILD syndrome). A new field of research is epigenetic mosaicism. Some familial cases of pigmentary mosaicism may reflect monoallelic autosomal expression. Early loss of heterozygosity explains type 2 segmental manifestation of autosomal dominant genodermatoses. On the other hand, superimposed segmental manifestation of polygenic disorders may originate either from allelic loss or from a postzygotic new mutation involving an additional predisposing locus. Examples of didymosis (twin spotting) include phacomatosis pigmentokeratotica and cutis tricolor. Finally, an updated list of monogenic skin disorders being elucidated at the molecular level is presented.