A Turkish trichothiodystrophy patient with homozygous XPD mutation and genotype-phenotype relationship.

Trichothiodystrophy (TTD) is a rare, recessive condition involving multiple organs and systems. Four genes associated with nuclear excision repair have been described in the molecular etiology of TTD. There is a significant heterogeneity of clinical and laboratory findings of TTD, even in individuals carrying the same mutation. Worldwide, approximately 120 cases have been reported, mostly from Western populations and the mutations are compound heterozygous. We herein present clinical and laboratory findings of a female patient with a homozygous mutation, R722W, in the XPD gene. To date, two patients who carry the same mutation have been reported. Our genotype-phenotype correlation study showed patients who carry R722W mutation have a more severe TTD phenotype than other types of mutations.