Haplotype Analysis Discriminates Genetic Risk for DR3-Associated Endocrine Autoimmunity and Helps Define Extreme Risk for Addison's Disease

Context: Multiple autoimmune disorders (e. g. Addison's disease, type 1 diabetes, celiac disease) are associated with HLA-DR3, but it is likely that alleles of additional genes in linkage disequilibrium with HLA-DRB1 contribute to disease. Objective: The objective of the study was to characterize major histocompatability complex (MHC) haplotypes conferring extreme risk for autoimmune Addison's disease (AD). Design, Setting, and Participants: Eighty-six 21-hydroxylase autoantibody-positive, nonautoimmune polyendocrine syndrome type 1, Caucasian individuals collected from 1992 to 2009 with clinical AD from 68 families (12 multiplex and 56 simplex) were genotyped for HLA-DRB1, HLA-DQB1, MICA, HLA-B, and HLA-A as well as high density MHC single-nucleotide polymorphism (SNP) analysis for 34. Main Outcome Measures: AD and genotype were measured. Result: Ninety-seven percent of the multiplex individuals had both HLA-DR3 and HLA-B8 vs. 60% of simplex AD patients (P = 9.72 x 10(4)) and 13% of general population controls (P = 3.00 x 10(19)). The genotype DR3/DR4 with B8 was present in 85% of AD multiplex patients, 24% of simplex patients, and 1.5% of control individuals (P = 4.92 x 10(-191)). The DR3-B8 haplotype of AD patients had HLA-A1 less often (47%) than controls (81%, P = 7.00 x 10(-5)) and type 1 diabetes patients (73%, P = 1.93 x 10(-3)). Analysis of 1228 SNPs across the MHC for individuals with AD revealed a shorter conserved haplotype (3.8) with the loss of the extended conserved 3.8.1 haplotype approximately halfway between HLA-B and HLA-A. Conclusion: Extreme risk for AD, especially in multiplex families, is associated with haplotypic DR3 variants, in particular a portion (3.8) but not all of the conserved 3.8.1 haplotype. (J Clin Endocrinol Metab 95: E263-E270, 2010)