Trichothiodystrophy, commonly called TTD, is a rare inherited condition that affects many parts of the body. The hallmark of this condition is hair that is sparse and easily broken.

Variants (also called mutations) in at least 10 genes have been found to cause trichothiodystrophy. Most cases of the photosensitive form of trichothiodystrophy result from variants 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 2 H (TFIIH) complex. This complex is involved in the repair of DNA damage, which can be caused by UV rays. The TFIIH complex also plays an important role in gene transcription, which is the first step in protein production.

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.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Published Date: April 06, 2023
Published By: National Institutes of Health