Encyclopedia
Trichothiodystrophy, which is commonly called TTD, is a rare inherited condition that affects many parts of the body. The hallmark of this condition is brittle hair that is sparse and easily broken. Tests show that the hair is lacking sulfur, an element that normally gives hair its strength.
- genetic conditions
1. Introduction
Trichothiodystrophy, which is commonly called TTD, is a rare inherited condition that affects many parts of the body. The hallmark of this condition is brittle hair that is sparse and easily broken. Tests show that the hair is lacking sulfur, an element that normally gives hair its strength.
The signs and symptoms of trichothiodystrophy vary widely. Mild cases may involve only the hair. More severe cases also cause delayed development, significant intellectual disability, and recurrent infections; severely affected individuals may survive only into infancy or early childhood.
Mothers of children with trichothiodystrophy may experience problems during pregnancy including pregnancy-induced high blood pressure (preeclampsia) and a related condition called HELLP syndrome that can damage the liver. Babies with trichothiodystrophy are at increased risk of premature birth, low birth weight, and slow growth.
2. Frequency
Trichothiodystrophy has an estimated incidence of about 1 in 1 million newborns in the United States and Europe. About 100 affected individuals have been reported worldwide.
3. Causes
Most cases of the photosensitive form of trichothiodystrophy result from mutations in one of three genes: ERCC2, ERCC3, or GTF2H5. The proteins produced from these genes work together as part of a group of proteins called the general transcription factor IIH (TFIIH) complex. This complex is involved in the repair of DNA damage, which can be caused by UV radiation from the sun. The TFIIH complex also plays an important role in gene transcription, which is the first step in protein production.
Mutations in the ERCC2, ERCC3, or GTF2H5 genes reduce the amount of TFIIH complex within cells, which impairs both DNA repair and gene transcription. An inability to repair DNA damage probably underlies the sun sensitivity in affected individuals. Studies suggest that many of the other features of trichothiodystrophy may result from problems with the transcription of genes needed for normal development before and after birth.
Mutations in at least one gene, MPLKIP, have been reported to cause a non-photosensitive form of trichothiodystrophy. Mutations in this gene account for fewer than 20 percent of all cases of non-photosensitive trichothiodystrophy. Little is known about the protein produced from the MPLKIP gene, although it does not appear to be involved in DNA repair. It is unclear how mutations in the MPLKIP gene lead to the varied features of trichothiodystrophy.
In some cases, the genetic cause of trichothiodystrophy is unknown.
4. Inheritance
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
5. Other Names for This Condition
- Amish brittle hair syndrome
- BIDS syndrome
- brittle hair-intellectual impairment-decreased fertility-short stature syndrome
- IBIDS
- PIBIDS
- TTD
This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/trichothiodystrophy
References
- Faghri S, Tamura D, Kraemer KH, Digiovanna JJ. Trichothiodystrophy: asystematic review of 112 published cases characterises a wide spectrum ofclinical manifestations. J Med Genet. 2008 Oct;45(10):609-21. doi:10.1136/jmg.2008.058743.
- Hashimoto S, Egly JM. Trichothiodystrophy view from the molecular basis of DNArepair/transcription factor TFIIH. Hum Mol Genet. 2009 Oct 15;18(R2):R224-30.doi: 10.1093/hmg/ddp390. Review.
- Itin PH, Sarasin A, Pittelkow MR. Trichothiodystrophy: update on thesulfur-deficient brittle hair syndromes. J Am Acad Dermatol. 2001Jun;44(6):891-920; quiz 921-4. Review.
- Kleijer WJ, Laugel V, Berneburg M, Nardo T, Fawcett H, Gratchev A, Jaspers NG,Sarasin A, Stefanini M, Lehmann AR. Incidence of DNA repair deficiency disorders in western Europe: Xeroderma pigmentosum, Cockayne syndrome andtrichothiodystrophy. DNA Repair (Amst). 2008 May 3;7(5):744-50. doi:10.1016/j.dnarep.2008.01.014.
- Kraemer KH, Patronas NJ, Schiffmann R, Brooks BP, Tamura D, DiGiovanna JJ.Xeroderma pigmentosum, trichothiodystrophy and Cockayne syndrome: a complexgenotype-phenotype relationship. Neuroscience. 2007 Apr 14;145(4):1388-96.
- Morice-Picard F, Cario-André M, Rezvani H, Lacombe D, Sarasin A, Taïeb A. New clinico-genetic classification of trichothiodystrophy. Am J Med Genet A. 2009Sep;149A(9):2020-30. doi: 10.1002/ajmg.a.32902. Review.
- Moslehi R, Signore C, Tamura D, Mills JL, Digiovanna JJ, Tucker MA, TroendleJ, Ueda T, Boyle J, Khan SG, Oh KS, Goldstein AM, Kraemer KH. Adverse effects of trichothiodystrophy DNA repair and transcription gene disorder on human fetaldevelopment. Clin Genet. 2010 Apr;77(4):365-73. doi:10.1111/j.1399-0004.2009.01336.x.
- Stefanini M, Botta E, Lanzafame M, Orioli D. Trichothiodystrophy: from basicmechanisms to clinical implications. DNA Repair (Amst). 2010 Jan 2;9(1):2-10.doi: 10.1016/j.dnarep.2009.10.005. Review.
