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.
Features of TTD can include photosensitivity, icthyosis, brittle hair and nails, intellectual impairment, decreased fertility and short stature. 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, is an autosomalrecessive inherited disease. It is nonphotosensitive. BIDS is characterized by brittle hair, intellectual impairment, decreased fertility, and short stature.:501 There is a photosensitive syndrome, PBIDS.
BIDS is associated with the gene MPLKIP (TTDN1).
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. (Chong Hai Tay was the Singaporean doctor who was the first doctor in South East Asia to have a disease named after him). Tay syndrome should not be confused with the Tay-Sachs disease.:485 It is an autosomalrecessivecongenital disease.:501 In some cases, it can be diagnosed prenatally. IBIDS syndrome is nonphotosensitive.
The photosensitive form is referred to as PIBIDS, and is associated with ERCC2 and ERCC3.
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. These type of defects can result in other rare autosomal recessive diseases like xeroderma pigmentosum and Cockayne syndrome.
^James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology (10th ed.). Saunders. p. 575. ISBN0-7216-2921-0.
^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. PMID17880036.