Autosomal recessive neuroectodermal disorders characterized by brittle sulfur-deficient hair associated with impaired intellect, decreased fertility, and short stature. It may include nail dystrophy, ichthyosis, and photosensitivity correlated with a NUCLEOTIDE EXCISION REPAIR defect. All individuals with this disorder have a deficiency of cysteine-rich KERATIN-ASSOCIATED proteins found in the interfilamentous matrix. Photosensitive trichothiodystrophy can be caused by mutation in at least 2 separate genes: ERCC2 PROTEIN gene and the related ERCC3. Nonphotosensitive trichothiodystrophy can be caused by mutation in the TTDN1 gene.