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Japanese case of Herlitz junctional epidermolysis bullosa that initially showed a few blisters on the limited area

mal junction (Fig. 1c). Electron microscopy showed separation below the lamina densa and reduced, hypoplastic, anchoring fibrils (Fig. 1e). Mutation analysis revealed compound heterozygous mutations in COL7A1: a nonsense mutation, g.3631 C>T, and a novel splice site mutation, IVS 86-2delAG. A heterozygous nonsense mutation, a C-to-T transition at nucleotide 3631 in exon 27, was found in the proband and his father (Fig. 1f), which changed a glutamine, the 1121th amino acid, to a stop codon (p.Q1211X). A novel splice site mutation at the splice acceptor site of the intron 85/exon 86 junction, IVS 86-2delAG, was detected in the proband and his mother (Fig. 1g), which was corroborated by restriction fragment length polymorphism analysis using BspCNI (New England Biolabs, Beverly, MA, USA) (Fig. 1h). The effect of this mutation was predicted by automated splice site analysis(https://splice.uwo.ca/), and abolition of the acceptor splice site was expected as information content (Ri) decreases from 9.6 to 0.3 bits. Consequently, in-frame skipping of exon 86 in COL7A1 leading to deletion of 27 amino acids was assumed. Dystrophic epidermolysis bullosa (DEB) is a heritable blistering skin disorder caused by mutations in the COL7A1 gene, which is inherited either in an autosomal dominant or recessive (RDEB) manner. DEB shows variable clinical presentations depending on the types and positions of the COL7A1 gene mutations. Mutational study of the COL7A1 gene has revealed some genotype–phenotype correlations. A severe, generalized form of RDEB, previously called the Hallopeau–Siemens type, usually results from truncation mutations (i.e. nonsense, frameshift and splice-site mutation) on both alleles in either a homozygous or, more commonly, a compound heterozygous state. Thus far, only one in-frame translation of exon 86 by splice site mutation has been reported (IVS86-2A>G). Exon 86, which consists of 69 bp and codes for 27 amino acids, is located on the triple-helical collagenous domain of type VII collagen. Generally, splice site mutations give rise to a milder phenotype, and the mutation found in our case was expected to result in a slightly curtailed polypeptide with intact NC1 and NC2 domains. However, why the mutation resulted in a loss of immunoreactivity is unclear. One possible reason is that the biopsy site was not a fresh blister. But the cause of the severe phenotype presented in the proband still remains unknown. Skipping of adjacent codon exon 87 by an A-to-G transition at nucleotide 6899 has been reported in a large Chinese family. Interestingly, they presented with clinical manifestations of DEB pruriginosa type with an autosomal dominant inheritance. In conclusion, we report a novel splice site mutation, IVS 86-2delAG, and a nonsense mutation, p.Q1211X, in the COL7A1 gene that resulted in the absence of type VII collagen and a severe generalized phenotype.