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Other names: Amish 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]

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][3]

Symptoms and signs

a) Frontal bossing,absent eyebrows b) sparse scalp hair c) onychoschizia of distal nail

Features of TTD can include photosensitivity, icthyosis, 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.[4] 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,[5] is an autosomal recessive[6] inherited disease. It is nonphotosensitive. BIDS is characterized by brittle hair, intellectual impairment, decreased fertility, and short stature.[7]: 501  There is a photosensitive syndrome, PBIDS.[8]

BIDS is associated with the gene MPLKIP (TTDN1).[9] 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.[10] (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.[7]: 485 [11][12][13] It is an autosomal recessive[14] congenital disease.[7]: 501 [15] In some cases, it can be diagnosed prenatally.[16] IBIDS syndrome is nonphotosensitive.


The photosensitive form is referred to as PIBIDS, and is associated with ERCC2[11] and ERCC3.[17]

Photosensitive forms

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.[18] These type of defects can result in other rare autosomal recessive diseases like xeroderma pigmentosum and Cockayne syndrome.[19]

DNA repair

Currently, mutations in four genes are recognized as causing the TTD phenotype, namely TTDN1, XPB, XPD and TTDA.[20] 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[21] (see DNA damage theory of aging).


The evaluation of this condition is done via the following:[22]

  • Detailed medical history
  • Physical exam
  • MRI imaging
  • Laboratory testing


In terms of management of an individual with this condition would benefit from the following:[22]

  • Protection from exposure to sun
  • Special education
  • Physical therapy
  • Skin softening emollients
  • Prophylactic antibiotics

See also


  1. 1.0 1.1 "Trichothiodystrophy". Genetics Home Reference. Archived from the original on 20 February 2018. 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. Giacaman, A.; Ferrando, J. (1 February 2022). "[Translated article] Keys to the Diagnosis of Hair Shaft Disorders: Part I". Actas Dermo-Sifiliográficas. 113 (2): T141–T149. doi:10.1016/ ISSN 0001-7310. PMID 35244576. Archived from the original on 20 April 2022. Retrieved 19 April 2022.
  4. 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.
  5. Online Mendelian Inheritance in Man (OMIM): 234050
  6. 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.
  7. 7.0 7.1 7.2 Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0-07-138076-0.
  8. Hashimo S, and Egly JM. Trichothiodystrophy view from the molecular basis of DNA repair transcription factor
  9. 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.
  10. 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.
  11. 11.0 11.1 Online Mendelian Inheritance in Man (OMIM): 601675
  12. Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 978-1-4160-2999-1.
  13. Hashimoto S, and Egly JM,
  14. 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.
  15. 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.
  16. 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.
  17. Online Mendelian Inheritance in Man (OMIM): 616390
  18. Hashimoto S, and Egly JM[permanent dead link]
  19. 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.
  20. 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.
  21. 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.
  22. 22.0 22.1 "Trichothiodystrophy". NORD (National Organization for Rare Disorders). Archived from the original on 26 February 2021. Retrieved 1 September 2021.

External links

External resources