Trichothiodystrophy (TTD) is an autosomal recessive inherited disorder characterised by brittle hair and intellectual impairment. The word breaks down into tricho – "hair", thio – "sulphur", and dystrophy – "wasting away" or literally "bad nourishment". TTD is associated with a range of symptoms connected with organs of the ectoderm and neuroectoderm. TTD may be subclassified into four syndromes: Approximately half of all patients with trichothiodystrophy have photosensitivity, which divides the classification into syndromes with or without photosensitivity; BIDS and PBIDS, and IBIDS and PIBIDS. Modern covering usage is TTD-P (photosensitive), and TTD.[2]

Other namesAmish brittle hair syndrome, BIDS syndrome, brittle hair–intellectual impairment–decreased fertility–short stature syndrome[1]
Autosomal recessive - en.svg
This condition is inherited in an autosomal recessive manner.[1]
SpecialtyDermatology, medical genetics Edit this on Wikidata


Features of TTD can include photosensitivity, ichthyosis, brittle hair and nails, intellectual impairment, decreased fertility and short stature. A more subtle feature associated with this syndrome is a "tiger tail" banding pattern in hair shafts, seen in microscopy under polarized light.[3] The acronyms PIBIDS, IBIDS, BIDS and PBIDS give the initials of the words involved. BIDS syndrome, also called Amish brittle hair brain syndrome and hair-brain syndrome,[4] is an autosomal recessive[5] inherited disease. It is nonphotosensitive. BIDS is characterized by brittle hair, intellectual impairment, decreased fertility, and short stature.[6]: 501  There is a photosensitive syndrome, PBIDS.[7]

BIDS is associated with the gene MPLKIP (TTDN1).[8] IBIDS syndrome, following the acronym from ichthyosis, brittle hair and nails, intellectual impairment and short stature, is the Tay syndrome or sulfur-deficient brittle hair syndrome, first described by Tay in 1971.[9] (Chong Hai Tay was the Singaporean doctor who was the first doctor in South East Asia to have a disease named after him.[citation needed]) Tay syndrome should not be confused with the Tay–Sachs disease.[6]: 485 [10][11][12] It is an autosomal recessive[13] congenital disease.[6]: 501 [14] In some cases, it can be diagnosed prenatally.[15] IBIDS syndrome is nonphotosensitive.


The photosensitive form is referred to as PIBIDS, and is associated with ERCC2[10] and ERCC3.[16]

Photosensitive formsEdit

All photosensitive TTD syndromes have defects in the nucleotide excision repair (NER) pathway, which is a vital DNA repair system that removes many kinds of DNA lesions. This defect is not present in the nonphotosensitive TTD's.[17] These type of defects can result in other rare autosomal recessive diseases like xeroderma pigmentosum and Cockayne syndrome.[18]

DNA repairEdit

Currently, mutations in four genes are recognized as causing the TTD phenotype, namely TTDN1, XPB, XPD and TTDA.[19] Individuals with defects in XPB, XPD and TTDA are photosensitive, whereas those with a defect in TTDN1 are not. The three genes, XPB, XPD and TTDA, encode protein components of the multi-subunit transcription/repair factor IIH (TFIIH). This complex factor is an important decision maker in NER that opens the DNA double helix after damage is initially recognized. NER is a multi-step pathway that removes a variety of different DNA damages that alter normal base pairing, including both UV-induced damages and bulky chemical adducts. Features of premature aging often occur in individuals with mutational defects in genes specifying protein components of the NER pathway, including those with TTD[20] (see DNA damage theory of aging).



See alsoEdit


  1. ^ a b "Trichothiodystrophy". Genetics Home Reference. Retrieved 19 February 2018.
  2. ^ Lambert WC, Gagna CE, Lambert MW (2010). "Trichothiodystrophy: Photosensitive, TTD-P, TTD, Tay syndrome". Adv Exp Med Biol. Advances in Experimental Medicine and Biology. 685: 106–10. doi:10.1007/978-1-4419-6448-9_10. ISBN 978-1-4419-6447-2. PMID 20687499.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ Liang, Christine; Kraemer, Kenneth H.; Morris, Andrea; Schiffmann, Raphael; Price, Vera H.; Menefee, Emory; DiGiovanna, John J. (February 2005). "Characterization of tiger tail banding and hair shaft abnormalities in trichothiodystrophy". Journal of the American Academy of Dermatology. 52 (2): 224–232. doi:10.1016/j.jaad.2004.09.013. PMID 15692466.
  4. ^ Online Mendelian Inheritance in Man (OMIM): 234050
  5. ^ Baden, H. P.; Jackson, C. E.; Weiss, L.; Jimbow, K.; Lee, L.; Kubilus, J.; Gold, R. J. (Sep 1976). "The physicochemical properties of hair in the BIDS syndrome". American Journal of Human Genetics. 28 (5): 514–521. PMC 1685097. PMID 984047.
  6. ^ a b c Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0-07-138076-0.
  7. ^ Hashimo S, and Egly JM. Trichothiodystrophy view from the molecular basis of DNA repair transcription factor
  8. ^ Nakabayashi K, Amann D, Ren Y, et al. (March 2005). "Identification of C7orf11 (TTDN1) gene mutations and genetic heterogeneity in nonphotosensitive trichothiodystrophy". Am. J. Hum. Genet. 76 (3): 510–6. doi:10.1086/428141. PMC 1196401. PMID 15645389.
  9. ^ Tay CH (1971). "Ichthyosiform erythroderma, hair shaft abnormalities, and mental and growth retardation. A new recessive disorder". Arch Dermatol. 104 (1): 4–13. doi:10.1001/archderm.104.1.4. PMID 5120162.
  10. ^ a b Online Mendelian Inheritance in Man (OMIM): 601675
  11. ^ Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 978-1-4160-2999-1.
  12. ^ Hashimoto S, and Egly JM,
  13. ^ Stefanini M, B. E.; Botta, E.; Lanzafame, M.; Orioli, D. (January 2010). "Trichothiodystrophy: from basic mechanisms to clinical implications". DNA Repair. 9 (1): 2–10. doi:10.1016/j.dnarep.2009.10.005. PMID 19931493.
  14. ^ James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology (10th ed.). Saunders. p. 575. ISBN 978-0-7216-2921-6.
  15. ^ Kleijer WJ, van der Sterre ML, Garritsen VH, Raams A, Jaspers NG (Dec 2007). "Prenatal diagnosis of xeroderma pigmentosum and trichothiodystrophy in 76 pregnancies at risk". Prenat. Diagn. 27 (12): 1133–1137. doi:10.1002/pd.1849. PMID 17880036. S2CID 23534246.
  16. ^ Online Mendelian Inheritance in Man (OMIM): 616390
  17. ^ Hashimoto S, and Egly JM[permanent dead link]
  18. ^ Peserico, A.; Battistella, P. A.; Bertoli, P. (1 January 1992). "MRI of a very rare hereditary ectodermal dysplasia: PIBI(D)S". Neuroradiology. 34 (4): 316–317. doi:10.1007/BF00588190. PMID 1528442. S2CID 31063628.
  19. ^ Theil AF, Hoeijmakers JH, Vermeulen W (2014). "TTDA: big impact of a small protein". Exp. Cell Res. 329 (1): 61–8. doi:10.1016/j.yexcr.2014.07.008. PMID 25016283.
  20. ^ Edifizi D, Schumacher B (2015). "Genome Instability in Development and Aging: Insights from Nucleotide Excision Repair in Humans, Mice, and Worms". Biomolecules. 5 (3): 1855–69. doi:10.3390/biom5031855. PMC 4598778. PMID 26287260.

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