MMP1 and trichothiodystrophy: Finally, alterations of MMP1 gene expression have been associated to disorders with skin defects: overexpression of MMP1 in primary dermal fibroblasts of patients with trichothiodystrophy is responsible for collagen type I degradation and altered wound healing features whereas a functional single nucleotide polymorphism in MMP1 promoter is associated with increased collagen type VII degradation and high severity of recessive dystrophic EB.