Which of the following HLA types is associated with IDDM?: (A) HLA DR3, DR4, (B) HLA B27, (C) HLA B47, (D) HLA DR2
Answer is A. Major susceptibility gene for Type 1 DM is located in the HLA region on chromosome 6. 95% of patients with IDDM express HLA DR3 or DR4. Concordance rate of Type 1 DM in identical twins ranges between 40- 60%. Type 2 DM has a strong genetic component. The concordance of type 2 DM in identical twins is between 70 and 90%. Reference: Harrison's Principles of Internal Medicine, 18th Edition chapter 344.