Trichothioystrophy is a rare genetic condition caused by mutations in either of the ERCC2/XPD and ERCC3/XPB genes. The symptoms of the disease result from a loss of nucleotide excision repair (NER) mechanisms, resulting in high sensitivity to UV light. Patients suffer from brittle hair and nails, ichthyotic or dry and scaly skin as well as physical and mental retardation. Skin cancers have been reported in several cases, associated with Trichothiodystrophy, which is also known as Tay syndrome.