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GENATLAS PHENOTYPE
last update : 25-01-2022
Symbol TTDA
Location 6q25.3
Name trichothiodystrophy group A
Other name(s)
  • ichthyosiform erythroderma with hair abnormality and mental and growth retardation
  • Tay syndrome
  • trichothiodystrophy, photosensitive
    • Corresponding gene GTF2H5
    Other symbol(s) IBIDS, TTDP
    Main clinical features
  • brittle hair and nails (because of reduced content of cysteine-rich matrix proteins), ichthyotic skin, and physical, microcephaly and hypomyelination and mental retardation, sulfur-deficient brittle hair and neuroectodermal symptoms
  • photosensitivity, ichthyosis, brittle hair, intellectual impairment, ocular abnormalities (cataract), decreased fertility, and short stature (Faghri 2008)
  • half of TTD patients exhibit photosensitivity, resulting from the defect in the nucleotide excision repair (Hashimoto 2009)
  • light microscopy test of hair shaft reveals trichoschisis; there is a cleaving, breaking, irregular and flattening hair surface like a trichorrhexis nodosa
    • Genetic determination autosomal recessive
    Function/system disorder dermatology
    mental retardation
    Type disease
    Gene product
    Name general transcription factor IIH, polypeptide 5
    Remark(s)
  • in TTDA cells repair is not fully compromised but only delayed (PMID: 21730288))