Genetic association of Canine Lymphocytic Thyroiditis (CLT) with DLA class II in Giant Schnauzer and Hovawart dogs

Abstract: Canine Lymphocytic Thyroiditis (CLT) resembles naturally occurring lymphocytic thyroiditis in White Leghorn chickens and Hashimoto's thyroiditis in man. It is a common autoimmune endocrine disease in dogs which is a result of destruction of the thyroid glands. Many autoimmune diseases show associations with the major histocompability complex (MHC) class II alleles. Within the canine Major Histocompatibility Complex (DLA) some of the class II genes are highly polymorphic. In this study an evaluation of the association between DLA class II haplotype and the risk for developing CLT has been performed by sequencing the polymorphic exon 2 form the genes DLA-DRB1, DLA-DQA1 and DQB1. Two high-risk breeds for developing CLT, Giant Schnauzer and Hovawart, have been analysed from a total of 198 dogs. Included in the study were 35 healthy controls, 3 borderline cases and 87 CLT-positive dogs. Results show that Giant Schnauzers carrying the haplotype DRB1'01201DQA1'00101DQB1'0020 have an increased risk to develop CLT, cases 22.5% versus controls 4.5%. This with an odds ratio = 6.0667 and with a p value = 0.015401 which shows that the increased risk to develop CLT is statistically significant. In Hovawart dogs the risk haplotype 01201'00401'013017 was present in 45 % (cases 43% versus controls 50%) of the total dogs analyzed. In this breed there was no evidence for an increased risk to develop CLT for dogs with this haplotype.