Relation between HLA and copy number variation of steroid 21-hydroxylase in a Swedish cohort of patients with autoimmune Addison's disease.
OBJECTIVE: Autoantibodies against the adrenal enzyme 21-hydroxylase is a hallmark manifestation in autoimmune Addison's disease (AAD). Steroid 21-hydroxylase is encoded by CYP21A2, which is located in the HLA region together with the highly similar pseudogene CYP21A1P. A high level of copy number variation is seen for the two genes, and therefore we asked if genetic variation of the CYP21 genes is associated with AAD.METHODS: Using next-generation DNA sequencing, we estimated the copy number of CYP21A2 and CYP21A1P together with HLA alleles in 479 Swedish patients with AAD and autoantibodies against 21-hydroxylase, and in 1,393 healthy controls.RESULTS: With 95% of individuals carrying two functional 21-hydroxylase genes, no difference in CYP21A2 copy number was found when comparing patients and controls. In contrast, we discovered a lower copy number of the pseudogene CYP21A1P among AAD patients (p = 5 x 10-44) together with associations of additional nucleotide variants in the CYP21 region. However, the strongest association was found for HLA-DQB1*02:01 (p = 9 x 10-63), which in combination with the DRB1*04:04-DQB1*03:02 haplotype imposed the greatest risk of AAD.CONCLUSIONS: We identified strong associations between copy number variants in the CYP21 region and risk of AAD, although these associations most likely are due to linkage disequilibrium with disease-associated HLA class II alleles.
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European journal of endocrinology