Abstract:

Objective To observe the ultrastructural features of recessive dystrophic epidermolysis bullosa inversa （RDEB-I） and to detect the mutations of COL7A1 gene in a family with RDEB-I. Methods A 24-year-old male patient complained of recurrent vesicles in the skin for 24 years. The lesions began as generalized pruritic vesicles and bullae soon after birth, with a predilection for areas subject to friction, and showed a trend to be worse in summer but mild in winter. No photosensitivity was observed. When he was 3 to 4 years old, the lesions were decreased in number, with the only involvement of the trunk and abdomen; thereafter, the lesions were improved year by year. The patient suffered from nephritis at the age of 5 years, which progressed into renal failure at the age of 15 years. He received renal transplantation and was given long-term oral tacrolimus and mycophenolate mofetil, which leaded to an improvement in the lesions. The family history was unremarkable, and the marriage between her parents was not consanguineous. Dermatological examination revealed large areas of irregularly-marginated, hypopigmented, atrophic scar on the waist, back and abdomen with onychodystrophy involving multiple nails. No vesicles were observed. Immunofluorescence antigen mapping and transmission electron microscopy were conducted to observe the expression of type VII collagen in and ultrastructure of cutaneous lesions from the patient. Venous blood samples were obtained from the patient as well as his parents and 3 sisters, and drill biopsy specimens were obtained from the margin of vesicular lesions and unaffected anterior tibial skin of the patient. DNA specimens were obtained from the blood samples of the family members and 150 unrelated healthy controls, and RNA was extracted from the biopsy samples of the patient. PCR and direct sequencing were carried out to detect mutations in COL7A1 gene, and reverse transcription-PCR was conducted to confirm the mutation at mRNA level. Results Skin cleavage was observed under lamina densa in the dermis, with a decrease in anchoring fibrils and expression of type Ⅶ collagen in the lesions of the patient. A heterozygous synonymous mutation c.C5499T which created a new splicing site and leaded to a premature terminal codon, as well as a heterozygous missense mutation c.C6205T（C-T transition at codon 2069: CGT to TGT）which leaded to the substitution of arginine by cysteine, were identified in the COL7A1 gene of the proband and all of his sisters, but not in any of the unrelated controls. The c.C5499T and c.C6205T mutations were inherited from the patient's father and mother respectively. Conclusion The compound heterozygous mutations c.C6205T and c.C5499T may be responsible for RDEB-I in this patient.

Key words: epidermolysis，bullosa，dystrophica，inversa