Review Article

Fungal Alterations in Inflammatory Bowel Diseases

Siu Lam; Tao Zuo; Martin Ho; Francis K. L. Chan; Paul K. S. Chan; Siew C. Ng


Aliment Pharmacol Ther. 2019;50(11):1159-1171. 

In This Article


The incidence of Crohn's disease (CD) and ulcerative colitis (UC), the two subtypes of IBD, is rising rapidly worldwide particularly in newly industrialised countries. However, the cause of this remains unclear.[1,2] Aetiological studies on IBD have elucidated the role of genetics, host immune response, gut microbiota and environmental triggers in disease pathogenesis.[3] Genetic loci including Nucleotide-binding oligomerisation domain-containing protein 2 (NOD2), interleukin 10 (IL-10) and Caspase recruitment domain-containing protein 9 (CARD9) have been associated with IBD,[4–10] but their effects on populations of different ethnicities and geography are heterogeneous.[1,11,12] Alterations in the gut microbiota and changes in environmental factors most likely account for the rapid emergence of IBD globally.[13] To date, tremendous efforts have been focused on delineating the role the of bacterial microbiome in IBD,[14] while studies of other components of the gut microbiota, including changes in fungi or "mycobiota" are scarce.[15] Although fungi only constitute approximately 0.1% of the total microorganisms in the gut,[16–18] they have been thought to also play a role in IBD pathogenesis.[19–23] In addition to intestinal inflammation, external factors including diet, antibiotics and immunosuppressive therapy can influence the structure or composition of mycobiota in patients with IBD. In this review, we discuss alterations in the mycobiota, also known as "fungal dysbiosis" in IBD, trans-kingdom interaction between fungi and other members of the gut microbiota and their potential role in the pathogenesis of IBD. We highlight the role of fungi and their functions in animal and human IBD and illustrated how environmental factors impact on the gut mycobiota.