Lethal acantholytic epidermolysis bullosa due to a novel homozygous deletion in DSP:expanding the phenotype and implications for desmoplakin function in skin and heart

Desmoplakin is the major linker in desmosomes in epithelia and myocardium, anchoring intermediate filaments by the C-terminus to plakoglobin and plakophilin in the desmosomal plaque. Mutations in the gene DSP encoding desmoplakin have been associated with various phenotypes affecting skin and/or heart. One of these phenotypes, lethal acantholytic epidermolysis bullosa (LAEB), is characterized by extensive postnatal shedding of epidermis leading to early demise and is caused by recessive mutations in the gene DSP resulting in truncation of the desmoplakin C-terminus. Here we describe two infants born to the same consanguinous parents who suffered extensive epidermal dislodgment and died shortly after birth. In addition, universal alopecia, anonychia, malformed ears and cardiomyopathy were observed. As the clinical diagnosis was LAEB, DSP mutation analysis was performed. A homozygous deletion (c.2874del5) abrogating the donor splice site of exon 20 was found. The deletion is predicted to cause read-through in intron 20 with subsequent recognition of a premature termination codon, resulting in desmoplakin lacking its rod domain and C-terminus (p.Lys959MetfsX5). Electron microscopic analysis of skin biopsies showed absence of the desmosomal inner dense plaque and lack of tonofilament insertion. This is the second report of LAEB. These findings suggest DSP mutations as the aetiology of LAEB and cardiomyopathy as part of the phenotype. Furthermore, they indicate that in addition to the desmoplakin C-terminus, the rod domain is dispensable for intrauterine development but is essential for the inner dense plaque of desmosomes.