Under recognized human intestinal spirochetosis and its connection with irritable bowel syndrome and colorectal neoplasms

Human Intestinal Spirochetosis (HIS) is an infection of colonic epithelial cells by Brachyspira pilosicoli and Brachyspira aalborgi, which is diagnosed by a characteristic blue haze present on the histological biopsies. The most common clinical manifestation of this infection is chronic diarrhea, but it may contribute to other known clinical entities such as Irritable Bowel Syndrome (IBS) and Sessile Serrated Adenomas (SSA), especially in immunocompromised patients. IBS is an intestinal disorder characterized by an onset of pain with changes in bowel habits, consistency etc. and with no clear etiology. HIS infection may be that etiology in some cases since there is a significant overlap of symptoms and a study in Sweden found that people with HIS were at a three times higher risk of developing IBS when compared to those without it. SSA can be associated with the development of high grade dysplasia and the progression to adenocarcinoma. The development of SSA is linked to a mutation in the BRAF gene, however distinct causes of the mutation have not been established. HIS may be one of those causes due to the induction of chronic inflammation, which would explain why a 2014 study conducted in Japan found that the rate of HIS infection was significantly higher in those with SSA than those that did not have it. Pathologists should have HIS on their mind when helping to treat patients with chronic diarrhea, but should also recognize the contribution this infection can have on people with IBS and sessile serrated adenomas.