Pollitt syndrome patients carry mutation in TTDN1

Complete human genome sequencing was used to identify the causative mutation in a family with Pollitt syndrome (MIM #275550), comprising two non-consanguineous parents and their two affected children. The patient's symptoms were reminiscent of the non-photosensitive form of recessively inherited trichothiodystrophy (TTD). A mutation in the TTDN1/C7orf11 gene, a gene that is known to be involved in non-photosensitive TTD, had been excluded by others by Sanger sequencing. Unexpectedly, we did find a homozygous single-base pair deletion in the coding region of this gene, a mutation that is known to cause non-photosensitive TTD. The deleterious variant causing a frame shift at amino acid 93 (C326delA) followed the right mode of inheritance in the family and was independently validated using conventional DNA sequencing. We expect this novel DNA sequencing technology to help redefine phenotypic and genomic variation in patients with (mono) genetic disorders in an unprecedented manner.