VIP and rheumatoid arthritis: In this sense, decreased serum VIP levels have been described in a variety of disorders, including rheumatic diseases, such as early RA (eRA) [12], SpA [13], juvenile idiopathic arthritis [14], and osteoarthritis (OA) [15]; inflammatory bowel diseases, such as ulcerative colitis [16,17]; Graves’ disease [17]; Chagas cardiomyopathy [18]; Parkinson’s disease [19]; and asthma [20].