Objective To identify mutations in keratin genes (KRT1 and KRT10) in a pair of twins with bullous congenital ichthyosiform erythroderma (BCIE),and to explore the relationship between the causative genes and phenotypes.Methods Clinical data were collected from a pair of twins with BCIE and their family members.Peripheral blood samples were obtained from the twins,their old brother and parents,and DNA was extracted from these blood samples.Polymerase chain reaction (PCR)was performed to amplify all the coding exons and their flanking sequences of the KRT1 and KRT10 genes,and 100 unrelated healthy persons served as controls.Results The 11-year-old male proband presented with recurrent blisters,hypertrophy and desquamation all over the body for 11 years.His twin brother had similar skin lesions.Skin examination of the proband showed diffuse erythema covered with thick scaly crusts on the trunk and extremities.Blisters,bullae and erosions due to ruptured blisters were observed locally with tenderness on palpation.There were obvious hyperkeratotic and hard lesions on the big joints of the extremities.Diffuse hyperkeratosis could be seen on the palms and soles.A mutation c.591 + 1G ＞ A was identified at position 1 in intron 1 of the KRT1 gene in the twins,but not in the 3 healthy family members or the 100 unrelated healthy controls.Conclusion The mutation c.591 + 1G ＞ A at position 1 in intron 1 of the KRT1 gene may contribute to the clinical phenotype of the twins with BCIE.