The two genes are HLA DQ2 and DQ8 (human leukocyte antigen). About 30-40% of people have one or both, but it is triggered in about 1% of the population. Mine was 14 years ago after getting H1N1. One needs to be eating gluten before the celiac panel bloodwork or the illioscopy of the small intestine (called a gluten challenge, for several weeks). When someone is very early stage celiac there is little or no damage (flattening) of the intestinal villi so scopes can be negative. The blood test looks mostly for elevated levels of TgG, IgA and IgG antibodies. A primary care doctor can run the bloodwork. It is hard to diagnose just from symptoms because there can be so many and varied effects.