A Correlation Between the Pathogenic Processes of Fibromyalgia and Irritable Bowel Syndrome in the Middle-Aged Population: A Systematic Review.

Irritable bowel syndrome (IBS) is a common pathology in middle-aged patients and a regular consultation in the gastroenterology office. The prevalence is high in females with a ratio of 2:1, and due to its multifactorial etiology, it is difficult to address the symptomatology. On the other hand, fibromyalgia syndrome (FMS) is a chronic widespread pain syndrome also prevalent in the female population, characterized by systemic symptoms. It is proven that 28-59 % of patients with FMS develop IBS at some point in their illness; on the other hand, 32-77% of those with IBS will develop FMS. Our study aims to compile information about the pathogenesis of these diseases and highlight their common processes to target these two illnesses potentially.  This systematic review comprises twenty-three studies published between 2017 and 2022, selected by electronic research with keywords and Medical Subject Headings (MESH) strategy. The articles were taken from PubMed, Pubmed Central (PMC), Medline, and Cochrane libraries and met the inclusion and exclusion criteria and the pertinent quality checklists. Of the reviewed studies, 10 were case-control, six were narrative reviews, three were systematic reviews, three were cross-sectional, and one was a cohort study. They investigated the correlation and similitudes in the pathogenic process between FMS and IBS. There are some similar mechanisms in the physiopathologies of IBS and FMS, where the immune system, especially the mast cells (MCs), along with their products, receptors, the inflammatory cells with their intermediaries, hormones, and neurotransmitters such as serotonin, act together pathologically. Also, the role of the microbiota is very important in this pathogenesis since dysbiosis alters the levels of serotonin in the body and can produce hyperstimulation of the autonomic nervous system. There are common associated factors in IBS and FMS, with evident symptoms presented in both syndromes such as fatigue, pain, hypersensitivity, depression, anxiety, and others, that could be correlated in a certain way. After this systematic review, we can conclude that the most accepted theories of the common pathogenesis are the role of serotonin and MCs with their inflammatory biomarkers, which can affect different parts of the body producing the characteristic symptomatology. Moreover, other pathogenic mechanisms such as the involvement of microbiota and dysregulation of the gut-brain axis have shown promising results, and further investigation should be made to support their role.