The prevalence of nonalcoholic fatty liver disease (NAFLD) has elevated considerably over the last few decades reflecting the increase in obesity and type II diabetes mellitus. It has become one of the most common indications for liver transplantation. The harmful effects of NAFLD are not just limited to the liver; it has been established as a systemic disease affecting multiple organs through protracted low-grade inflammation facilitated by the metabolic activity of excessive fat tissue. 

Plethora of studies have reviewed extrahepatic manifestations of NAFLD such as cardiovascular disease, polycystic ovarian syndrome, chronic kidney disease, and hypothyroidism. Although mounting evidence showed patients with decompensated cirrhosis are at high risk for infectious complications, the evidence is scarce in patients with NAFLD (without advanced fibrosis or cirrhosis).Currently, it has also become evident that patients suffering from NAFLD might be at increased risk of developing various infections. The hypothesis suggests that this interrelationship includes links through hyperglycemia, insulin resistance, alterations in innate immunity, obesity, and vitamin D deficiency. In addition, a risk irrespective of these factors mediated by modifications in gut microbiota might play an important role in increasing burden of infections in these individuals.  

The study reviewed current knowledge on several infections including urinary tract infection, pneumonia, Helicobacter pylori, coronavirus disease 2019, and Clostridioides difficile as they are associated with NAFLD. The risk of few infections such as pneumonia or UTI exist mainly through the shared pathophysiology with T2DM and obesity. In other infections such as Clostridioides difficile colitis (CDC), it appears that alteration in microbiota in those with NAFLD enhance colonization of Clostridioides difficile and the development of infection. Increased and deregulated cytokine activity in COVID-19 has been the main denominator for higher mortality, and patients with NAFLD seem to be particularly vulnerable. Moreover, low-grade inflammation and cytokine derangements contribute in inflammatory skin changes such as Hidradenitis suppurativa (HS). However, more data through more rigorous researches is warranted to address the information regarding the risk of infection in COVID-19 population. Establishing this association can further aid in implementing strategies for treatment and prevention.

Source: Adenote A, Dumic I, Madrid C, Barusya C, Nordstrom CW, Rueda Prada L. NAFLD and Infection, a Nuanced Relationship. Can J Gastroenterol Hepatol. 2021 Apr 15;2021:5556354.