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Trichothiodystrophy - Hair and Scalp
See also in: Overview
Other Resources UpToDate PubMed

Trichothiodystrophy - Hair and Scalp

See also in: Overview
Contributors: Gabriela Ulloa MD, Loren Krueger MD, Susan Burgin MD
Other Resources UpToDate PubMed


Trichothiodystrophy (TTD, also known as Tay syndrome) is a rare, autosomal recessive congenital disorder that results in short, brittle, sulfur-deficient hair and various other associated clinical features. Presentation ranges from mild cases with fractured, brittle hair only to brittle hair with severe systemic complications characterized by the acronym PIBIDS:
  • Photosensitivity
  • Ichthyosis
  • Brittle hair
  • Intellectual impairment with low IQ
  • Decreased fertility
  • Short stature
Approximately half of TTD patients experience photosensitivity due to a defective nucleotide excision repair. Mutations in ERCC2, ERCC3, and GTF2H5 genes producing XPB, XPD, and p8/TTDA subunits of the general transcription factor IIH (TFIIH) are responsible for photosensitive TTD. The ineffective DNA repair likely leads to photosensitivity. Although less frequent, non-photosensitive TTD patients have been shown to have mutations in TTDN1 or MPLKIP, genes of unknown function.

Dry, scaly, and/or thickened skin was reported in 65% of patients (out of 112 in a review).

Brittle hair
Short, brittle hair due to sulfur deficiency is a diagnostic characteristic of TTD. It results in "tiger tail" banding in the hair – alternating light and dark bands seen under polarizing light. Hair may be sparse and alopecia may be seen.

Intellectual impairment
Most patients have a form of intellectual impairment, such as failure to reach developmental milestones and low IQ. Microcephaly, abnormal gait, and increased tendon reflexes have also been reported. On neuroimaging, some TTD patients demonstrated impaired development of the brain with features such as demyelination and cerebellar atrophy.

Decreased fertility
Up to 14% of patients experienced sexual / reproductive abnormalities, primarily hypogonadism. Fertility is decreased. Of those who achieved gestation, approximately half experienced pregnancy complications, such as preeclampsia, and around 50% of the infants had abnormal birth characteristics, such as low birth weight, premature birth, collodion membrane, and congenital cataracts, usually indicating TTD inheritance in the baby.

Short stature and facial abnormalities
TTD patients generally have a short stature and an unusual facial appearance, including a beaked nose, protruding ears, and a receding chin.

Additional systemic features observed
  • Recurring infections, predominantly respiratory, contributing to increased neonatal and childhood morbidity and mortality
  • Ocular abnormalities, primarily cataracts at all ages
  • Seizure disorder, primarily in patients with a mutated TTDN1 gene
  • Dental abnormalities and caries
  • Cardiac and hepatic abnormalities


Q84.1 – Congenital morphological disturbances of hair, not elsewhere classified

723551003 – Trichothiodystrophy

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Differential Diagnosis & Pitfalls

Polarizing microscopy is essential to differentiate between hair disorders that closely resemble TTD:
  • Trichorrhexis nodosa – The most common structural hair abnormality. With dermatoscope, weakened portions of the hair shaft with fraying causing breakage of the hair are observed.
  • Pili annulati – An autosomal dominant disorder presenting with striped, light and dark patterning with dermatoscope. Not all hair is affected. Patients do not present with concomitant symptoms.
  • Menkes syndrome – X-linked disorder associated with defective copper transport resulting in sparsely distributed, short, fragile hair with a wool-like quality. Pilli torti, flattened and twisted hairs, are seen under dermatoscope.
  • Monilethrix – An autosomal dominant condition causing short, brittle hair due to defective keratin genes. Under dermatoscope, elliptical nodes are present on the hair shaft, resulting in a beaded appearance.
  • Trichorrhexis invaginata – Intussusception within the hair shaft results in a ball and socket deformity causing short, sparse hair seen under dermatoscope. This is a finding in Netherton syndrome, which also has ichthyosis as a characteristic.
Additional considerations:
Xeroderma pigmentosum (XP) can resemble TTD due to photosensitivity and neurologic impairment. Both disorders are caused by mutations in DNA repair genes. XP lacks the brittle, sulfur-deficient hair characteristic of TTD.

Cockayne syndrome can resemble TTD due to similar features such as prominent ears, short stature, ocular abnormalities, and immature sexual development. Although Cockayne patients are sun sensitive, they are not as affected as photosensitive TTD patients. The differentiating factor in Cockayne is the normal presentation at birth and subsequent postnatal failure of brain growth. Cockayne syndrome does not present with brittle hair.

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Last Reviewed:01/01/2018
Last Updated:01/29/2018
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Trichothiodystrophy - Hair and Scalp
See also in: Overview
A medical illustration showing key findings of Trichothiodystrophy : Brittle hair, Photosensitivity, Short stature, Ichthyosis
Clinical image of Trichothiodystrophy - imageId=2153102. Click to open in gallery.
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