Some of the proposed reasons are flatworm and hookworm infection, H. Pylori infection, gastrointestinal bleeding and their vitamin intake being disrupted by the incorporation of modern high-starch foods to the diet.
This type is extranodal - mostly happening in the lining of the stomach among individuals with chronic inflammation, like those with Helicobacter pylori infection, a bacteria that causes chronic gastritis.
And then I got this, I went to this doctor in California who diagnosed me with H pylori, and then a fungal and a bacterial overgrowth in my small intestines.