Zhulina and colleagues [33] have shown activation of the NF-κB pathway and increased neutrophil activity (as measured by myeloperoxidase [MPO]) in intestinal tissues of a large proportion of discordant twin siblings of CD and UC patients when compared to healthy controls—this providing additional evidence that many “healthy” FDR of IBD patients bear a subclinical inflammation. Here, MPO is linked to irritable bowel syndrome.