What is the first step in the proposed pathophysiology of enteropathic arthritis?

• A. Gut inflammation damages the intestinal barrier
• B. Bacterial antigens travel to joints
• C. Molecular mimicry
• D. Autoimmune reaction in the joints

Answer: (A)

The starting event is gut inflammation causing damage to the intestinal barrier. When the barrier is compromised, bacterial antigens and other microbial products can cross into the circulation and lymphoid tissue, triggering systemic immune activation. This primed immune response can then target the joints, leading to enteropathic arthritis. So, barrier disruption is the initiating step. The idea that bacterial antigens travel to the joints describes what happens after, not the first step; molecular mimicry is a potential mechanism by which the immune response may cross-react with joint tissue, and autoimmune joint inflammation is the downstream consequence of this systemic immune activation.