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Of eight leprosy susceptibility loci identified by genome-wide association studies, five have been implicated in Crohn disease, suggesting a common genetic fingerprint between leprosy and inflammatory bowel disease (IBD). Here, we conducted a multiple-stage genetic association study of 133 IBD susceptibility loci in multiple leprosy samples (totaling 4,971 leprosy cases and 5,503 controls) from a Chinese population and discovered two associations at rs2058660 on 2q12.1 (p = 4.57 × 10(-19); odds ratio [OR] = 1.30) and rs6871626 on 5q33.3 (p = 3.95 × 10(-18); OR = 0.75), implicating IL18RAP/IL18R1 and IL12B as susceptibility genes for leprosy. Our study reveals the important role of IL12/IL18-mediated transcriptional regulation of IFN-γ production in leprosy, and together with previous findings, it demonstrates the shared genetic susceptibility between infectious and inflammatory diseases.

Summary Background Dyschromatosis symmetrica hereditaria (DSH) is a rare autosomal dominantly inherited dermatosis and characterized by a mixture of hyperpigmented and hypopigmented macules on the back of hands and feet. The DSH locus was mapped to chromosome 1q21 and subsequently pathogenic mutations were identified in the adenosine deaminase acting on RNA1 ( ADAR1 ) gene in 2003. Objective In this study, we performed a mutation analysis of the ADAR1 gene in eight Chinese families and one sporadic patient with typical DSH. Methods PCR and direct sequencing of the ADAR1 gene were performed to identify and confirm the mutations in the eight families and the sporadic patient. Results Six novel and one known mutations were identified, including four missense mutations (p.K1105N, p.G1047R, p.F1099L, p.G1068R), two frameshift mutations (p.Q779fs-792x, p.P441fs-463x) and one nonsense mutation (p.R1096x). Conclusion Six novel mutations were found in five unrelated families and one sporadic case, which have further improved our understanding on the role of ADAR1 in DSH. Interestingly, we failed to detect any mutations of ADAR1 in two families.