Look into Behçet's disease. Patients with Behçet's can have neurological manifestations, GI manifestations, skin problems, joint pain, mouth ulcers, and thyroid problems, and typically have high ASCA IGG antibodies. Usually, ASCA IGG can indicate Crohn's or ulcerative colitis, but if signs of Crohn's or UC are not found or indicated from a colonoscopy and/or endoscopy, the differential diagnosis is Behçet's.