A Photosensitivite Trichothiodystrophy Patient With A Mutation in ERCC2 Gene

Objectives: Photosensitive Trichothiodystrophy(PS-TTD) is a rare autosomal reccesively inherited disease caused by three genes encoding different subunits of transcription factor TFIIH complex(ERCC2, ERCC3, GTF2H5). We present a 15-years old boy with sun sensitivity, mental and physical developmental delay, and tiger tail apperence of his hair under polarized light microscopy. Methods:A 15-years old boy present with microcephaly, mental and physical developmental delay, skin lesions, photosensitivity and also photophobia. His parents were first degree cousins. On physical examination, his entire body was covered by the dry skin. Ichthyosis was remarkable in his neck and ears. His hair was brittle. He had not having haircut for a long time. He had receding chin, prominent nose, large eyes, protruding ears, dystrophic nails. Diffüze signal hyperintensity of white matter was detected on MRI. We encountered tiger tail apperence in his hair examination under polarized light microscopy. Results:Trichothiodystrophy was suspected and a gene panel containing Xeroderma Pigmentosum related genes was carried out. We obtained a homozygous likely pathogenic c.334C>T (p.Arg112Cys; rs760820378) variant in exon 5 of ERRC2. Conclusions:ERCC2 gene is a subunit of transcription factor TFIIH complex which plays role in both nucleotide excision repair and transcription. This gene also causes XP and Cockayne syndrome phenotypes. We considered primarily PS-TTD disease in our patient due to the tiger tail apearence under polarized microscope and physical findings. However there are patients have features of more than one disease. Therefore, we decided to follow patient for any potential skin malignancy which is a feauture of XP.
Keywords: ERCC2 Gene, Photosensitive Trichothiodystrophy, tiger tail