{"version":"v1","chain":{"id":"independent-cooccurrence-chain","title":"(Competing) SIBO + MCAS as independently co-occurring, not shared-driver","question":"What if SIBO and MCAS just co-occur because of shared upstream barrier failure, not a shared molecule?","summary":"Alternative to the H₂S-shared-driver hypothesis: barrier failure independently sets up both conditions; no single molecular driver is required.","steps":[{"nodeId":"concept:gut-barrier-dysfunction","rationale":"Barrier failure increases antigen exposure and microbial translocation.","evidence":"established"},{"nodeId":"concept:sibo-host-capacity-model","rationale":"Same barrier failure permits proximal microbial expansion.","evidence":"mechanistic-inference"},{"nodeId":"concept:mcas-histamine-patterns","rationale":"Same barrier failure independently primes mucosal mast cells.","evidence":"mechanistic-inference"}],"competingChains":["h2s-shared-driver-chain"],"relatedConcepts":["gut-barrier-dysfunction","mcas-histamine-patterns"],"relatedArticles":[],"evidenceFloor":"mechanistic-inference","lastReviewed":"2026-05-11"}}