Alessio Fasano, a gastroenterologist and leading expert on celiac and autoimmunity, has written a very accessible and short article on the subject. I can't find the entire article online, even though it's only a few pages long. Here is a link to the one I have in mind: Leaky gut and autoimmune diseases. - PubMed - NCBI. Think of it as a triangulation between genetic susceptibility, environmental triggers and the gut. As the abstract of the article states, "This new paradigm subverts traditional theories underlying the development of these diseases and suggests that these processes can be arrested if the interplay between genes and environmental triggers is prevented by re-establishing the zonulin-dependent intestinal barrier function."

What's interesting is that traditional medicine has thought this in one form or other for centuries going back to ancient China and Greece. Fasano's account is more detailed, nuanced and based on trials and conventional science, so it's a step forward. But what remains true is that intestinal permeability and zonulin deregulation are key to this terrible process.

I have SFN likely of autoimmune etiology, though still not certain, and I have had great results from healing my gut. Diet and supplementation aimed at healing my intestinal barrier, so leaky gut, has been the only thing helping me so far and allowing me to avoid meds entirely and to live relatively normal life, emphasis on 'relatively', since SFN takes a lot out of you. But perhaps in a few years time I'll be in a better place. Healing the damage I've done to my gut over many years will take many years itself.

Here's an article by him that I could locate: Zonulin, regulation of tight junctions, and autoimmune diseases

Good luck!