New clinico-genetic classification of trichothiodystrophy

Authors

  • Fanny Morice-Picard,

    Corresponding author
    1. Department of Pediatric Dermatology, National Reference Center for Rare Skin Disorders, Pellegrin University Hospitals, Bordeaux, France
    2. Department of Medical Genetics (National Reference Center for Developmental Defects), Pellegrin University Hospitals, Bordeaux, France
    • National Reference, Center for Rare Skin Disorders, Unité de Dermatologie Pédiatrique, Hopital Pellegrin-Enfants, 33076 Bordeaux, France.
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  • Muriel Cario-André,

    1. INSERM U876, Victor Segalen Bordeaux 2 University, Bordeaux, France
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  • Hamid Rezvani,

    1. INSERM U876, Victor Segalen Bordeaux 2 University, Bordeaux, France
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  • Didier Lacombe,

    1. Department of Medical Genetics (National Reference Center for Developmental Defects), Pellegrin University Hospitals, Bordeaux, France
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  • Alain Sarasin,

    1. CNRS FRE 2939, University Paris-Sud, Gustave Roussy Institute, Villejuif, France
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  • Alain Taïeb

    1. Department of Pediatric Dermatology, National Reference Center for Rare Skin Disorders, Pellegrin University Hospitals, Bordeaux, France
    2. INSERM U876, Victor Segalen Bordeaux 2 University, Bordeaux, France
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  • How to cite this article: Morice-Picard F, Cario-André M, Rezvani H, Lacombe D, Sarasin A, Taïeb A. 2009. New clinico-genetic classification of trichothiodystrophy. Am J Med Genet Part A 149A:2020–2030.

Abstract

Trichothiodystrophy (TTD) is a congenital hair dysplasia with autosomal recessive transmission. Cross banding pattern under polarized light plus trichoschisis and a low sulfur content of hair shafts define the disorder, which is associated with variable and neuroectodermal symptoms. So-called photosensitive forms of TTD (with low level of in vitro UV-induced DNA repair, not constantly associated with marked clinical photosensitivity) are caused by mutations in genes encoding subunits of the transcription/repair factor IIH (TFIIH). Ten percentage of nonphotosensitive patients are known to have TTDN1 mutations, the specific role of which is unknown. We studied nine patients recruited at our institution and reviewed 79 with molecular analysis out of 122 TTD patients reported in literature with the aim to collect systematically the clinical findings in TTD patients and establish genotype–phenotype correlations. The frequency of congenital ichthyosis, collodion-baby type, was significantly higher in the TFIIH mutated group. Hypogonadism was significantly more frequent in the non-photosensitive group. There was no statistical difference regarding osseous anomalies. Mutations in TFIIH sub-units leading to abnormal expression in genes involved in epidermal differentiation could explain the particular dermatological changes seen in photosensitive cases of TTD. We suggest a new clinico-genetic classification of TTD, which may help clinicians confused by the current acronyms used (IBIDS, PIBIDS…). Understanding the TTD ichthyotic phenotype could lead to therapeutic advances in the management of TTD and other types of ichthyoses. © 2009 Wiley-Liss, Inc.

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