American Board of Internal Medicine (ABIM) Certification Practice Exam

What autoantibody is characteristic of type 1 diabetes mellitus (DM1)?

1. Anti-Jo-1

2. Anti-GAD-65

3. Anti-SRP

4. Anti-Mi-2

The correct answer is: Anti-GAD-65

The characteristic autoantibody associated with type 1 diabetes mellitus is the anti-glutamic acid decarboxylase-65 (anti-GAD-65) antibody. Type 1 diabetes is primarily an autoimmune condition where the immune system mistakenly attacks the insulin-producing beta cells of the pancreas. This leads to a deficiency of insulin. Anti-GAD-65 antibodies are commonly found in individuals with type 1 diabetes, and their presence can aid in the diagnosis of this condition, particularly in patients who are not immediately presenting with classic symptoms. The detection of these antibodies is also helpful in distinguishing type 1 diabetes from type 2 diabetes and other forms of diabetes that present later in life. In contrast, the other antibodies listed are associated with different autoimmune conditions. For example, anti-Jo-1 antibodies are commonly found in polymyositis or dermatomyositis, anti-SRP antibodies are associated with a specific type of myopathy, and anti-Mi-2 antibodies are linked to dermatomyositis specifically. Understanding the specific associations of these autoantibodies helps clinicians make accurate diagnoses and determine appropriate management strategies for various autoimmune conditions.