Trichothiodystrophy

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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.[1]

Presentation

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.[2] 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,[3] is an autosomal recessive[4] inherited disease. It is nonphotosensitive. BIDS is characterized by brittle hair, intellectual impairment, decreased fertility, and short stature.[5]Template:Rp There is a photosensitive syndrome, PBIDS.[6]

BIDS is associated with the gene MPLKIP (TTDN1).[7] 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.[8] (Chong Hai Tay was the Singaporean doctor who was the first doctor in South East Asia to have a disease named after him.[9]) Tay syndrome should not be confused with the Tay–Sachs disease.[5]Template:Rp[10][11][12] It is an autosomal recessive[13] congenital disease.[5]Template:Rp[14] In some cases, it can be diagnosed prenatally.[15] IBIDS syndrome is nonphotosensitive.

Cause

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

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

DNA repair

Currently, mutations in four genes are recognized as causing the TTD phenotype, namely TTDN1, ERCC3/XPB, ERCC2/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).

Non-Photosensitive forms

The non-photosensitive forms are caused by AARS1, CARS1, TTDN1, RNF113A, TARS1 and MARS1 genes.[21] The function of AARS1, CARS1 and TARS1 gene are to charge tRNAs with amino acid.[22] According to one study, the TTDN1 gene plays role in mitosis.[23] Some study suggests that the RNF113A gene is a part of spliceosome and it can terminate CXCR4 pathway through CXCR4 Ubiquitination.[24][25][26]

RNF113A causes X-linked recessive form of TTD.[27]

Diagnosis

The diagnosis of TTD can by made by showing low sulfur content by biochemical assay of hair shafts, also, it can by following findings:[28]

  • Trichoschisis (broken or split hairs)
  • Alternating light and dark bands called 'tiger-tail pattern' are found in the hair shaft, which can be detected by polarised light microscopy or trichoscopy.
  • A severely damaged or absent hair cuticle can be seen by electron microscopy scanning.

Treatment

This disease doesn't have a cure, although it can be managed symptomatically.[29] Patients with Photosensetive forms should be provided with sun protection.[29][30]

See also

References

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  1. ↑ Script error: No such module "citation/CS1".
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  3. ↑ Online Mendelian Inheritance in Man (OMIM): 234050
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  5. ↑ a b c Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. Template:ISBN.
  6. ↑ Hashimo S, and Egly JM. Trichothiodystrophy view from the molecular basis of DNA repair transcription factor TF11H.www.oxfordjournals.org/content/18/R2/R224
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ https://www.sma.org.sg/UploadedImg/files/Publications%20-%20SMA%20News/4506/Interview.pdf
  10. ↑ a b Online Mendelian Inheritance in Man (OMIM): 601675
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Hashimoto S, and Egly JM, www.oxfordjournals.org/content/18/R2/R224
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Online Mendelian Inheritance in Man (OMIM): 616390
  17. ↑ Hashimoto S, and Egly JM http://www.oxfordjournals.org/content/18/R2/R224Script error: No such module "Unsubst".
  18. ↑ Script error: No such module "Citation/CS1".
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  27. ↑ Script error: No such module "Citation/CS1".
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  29. ↑ a b Script error: No such module "Citation/CS1".
  30. ↑ Script error: No such module "citation/CS1".

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External links

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