Gut microbiota and COVID-19: An intriguing pediatric perspective.

Gastrointestinal (GI) involvement has been reported in approximately 50% of patients with coronavirus disease 2019 (COVID-19), which is due to the pathogenic role of inflammation and the intestinal function of the angiotensin-converting enzyme 2 and its receptor. Accumulating adult data has pointed out that gut dysbiosis might occur in these patients with a potential impact on the severity of the disease, however the role of gut microbiota in susceptibility and severity of COVID-19 disease in children is still poorly known. During the last decades, the crosstalk between gut and lung has been largely recognized resulting in the concept of "gut-lung axis" as a central player in modulating the development of several diseases. Both organs are involved in the common mucosal immune system (including bronchus-associated and gut-associated lymphoid tissues) and their homeostasis is crucial for human health. In this framework, it has been found that the role of GI dysbiosis is affecting the homeostasis of the gut-liver axis. Of note, a gut microbiome imbalance has been linked to COVID-19 severity in adult subjects, but it remains to be clarified. Based on the increased risk of inflammatory diseases in children with COVID-19, the potential correlation between gut microbiota dysfunction and COVID-19 needs to be studied in this population. We aimed to summarize the most recent evidence on this striking aspect of COVID-19 in childhood.