The photosensitive form is referred to as PIBIDS, and is associated with ERCC2 and ERCC3. Photosensitive forms All photosensitive<unk>  syndromes have defects in the nucleotide excision repair (NER) pathway, which is a vital DNA repair system that removes many kinds of DNA lesions. This defect is not present in the nonphotosensitive<unk> 's. These type of defects can result in other rare autosomal recessive diseases like xeroderma pigmentosum and Cockayne syndrome. DNA repair Currently, mutations in four genes are recognized as causing the<unk>  phenotype, namely<unk> N1, XPB, XPD and<unk> A. Individuals with defects in XPB, XPD and<unk> A are photosensitive, whereas those with a defect in<unk> N1 are not. The three genes, XPB, XPD and<unk> A, encode protein components of the multi-subunit transcription/repair factor IIH (TFIIH). This complex factor is an important decision maker in NER that opens the DNA double helix after damage is initially recognized. NER is a multi-step pathway that removes a variety of different DNA damages that alter normal base pairing, including both UV-induced damages and bulky chemical adducts. Features of premature aging often occur in individuals with mutational defects in genes specifying protein components of the NER pathway, including those with<unk>  (see DNA damage theory of aging).
Trichothiodystrophy
Xeroderma pigmentosum
Tardive dysmentia
Fragile X syndrome
Acorea, microphthalmia and cataract syndrome
Fragile X-associated tremor/ataxia syndrome
Huntington's disease-like syndrome
Rett syndrome