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A hereditary condition characterized by sparse and brittle hair, short stature, and mental retardation.
Patients with trichothiodystrophy (TTD) have photosensitivity, short
stature, mental retardation and sulphur deficient brittle hair. TTD is not
associated with cancer. Cells from TTD patients are hypersensitive to
killing by UV and have defective DNA excision repair. The genes that are
defective in TTD have been found to be in XP complementation group D or in
unique TTD complementation groups. The explanation for the marked
differences in clinical features of patients with mutations in the same
The human diseases Xeroderma Pigmentosum, Cockayne syndrome, and Trichothiodystrophy are caused by mutations in a set of interacting gene products, which carry out the process of nucleotide excision repair.
The genes have now been cloned and many mutations in the genes identified.
The relationships between the distribution of mutations in the genes and the clinical presentations can be used for understanding the functions and the modes of interaction among the gene products.