A potential explanation is that TNFSF15 polymorphisms (a so-called IBD gene that is upregulated in lymphocytes as well as in macrophages of the intestinal lamina propria in patients with CD), which are common in Asian populations, are independent predictive risk factors for the development of PAF, and are therefore associated with a higher risk of PAF [51,52]. This evidence concerns the gene TNFSF15 and inflammatory bowel disease.