In pretibial dystrophic epidermolysis bullosa (PDEB), which is a rare subtype of dystrophic epidermolysis bullosa, the clinical and ultrastructural features are accounted for by quantitatively reduced or morphologically abnormal anchoring fibrils. A 39-year-old Japanese woman presented with a history of blisters, erosion, and atrophic scars on the anterior aspects of her legs, accompanied by variable itching. Her toenails were thickened and dystrophic, but her teeth and hair were normal. Her father had a history of similar blistering in the pretibial areas. Electron microscopy of the perilesional skin showed sparse and reduced density of the anchoring fibrils. A peripheral blood sample was taken to extract genomic DNA to examine for mutations in the type VII collagen gene (
COL7A1). We identified a G-to-T transversion at the nuculeotide position 5318, which results in a glycine-to-valine substitution (G1773V) in exon 61. The G1773V mutation has not been previously reported in PDEB. A missense mutation in
COL7A1 impedes the synthesis of type VII procollagen and its subsequent assembly into homotrimers and hence into anchoring fibrils. A clear understanding of this rare subtype is important in establishing the correct diagnosis, as well as in enabling genetic counseling and planning clinical management. Examination at the molecular level should also improve understanding of still unexplained clinical phenomena, such as the predilection toward the pretibial area, and the presence of lichenoid papules.
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