In particular, the locus containing the PTGER4 gene, which encodes the PG E2 receptor (subtype 4), was one of the first to be identified as a risk factor for CD, and then shown to be associated with both CD and UC phenotypes [12,17] and is the predominant locus in genetic studies of IBD in African Americans [26,39]. The gene discussed is PTGER4; the disease is inflammatory bowel disease.