GI Involvement May Signal Risk for MIS-C After COVID

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While evaluating an adolescent who had endured a several-day history of vomiting and diarrhea, I mentioned the likelihood of a viral causation, including SARS-CoV-2 infection. His well-informed mother responded, "He has no respiratory symptoms. Does COVID cause GI disease?"

Indeed, not only is the gastrointestinal (GI) tract a potential portal of entry of the virus but it may well be the site of mediation of both local and remote injury and thus a harbinger of more severe clinical phenotypes.

As we learn more about the clinical spectrum of COVID, it is becoming increasingly clear that certain features of GI tract involvement may allow us to establish a timeline of the clinical course and perhaps predict the outcome.

The GI Tract's Involvement Isn't Surprising

The ways in which the GI tract serves as a target organ of SARS-CoV-2 have been postulated in the literature. In part, this is related to the presence of abundant receptors for SARS-CoV-2 cell binding and internalization. The virus uses angiotensin-converting enzyme 2 (ACE-2) receptors to enter various cells. These receptors are highly expressed on not only lung cells but also enterocytes. Binding of SARS-CoV-2 to ACE-2 receptors allows GI involvement, leading to microscopic mucosal inflammation, increased permeability, and altered intestinal absorption.

The clinical GI manifestations of this include anorexia, nausea, vomiting, diarrhea, and abdominal pain, which may be the earliest, or sole, symptoms of COVID-19, often noted before the onset of fever or respiratory symptoms. In fact, Ong and colleagues, in a discussion about patients with primary GI SARS-CoV-2 infection and symptoms, use the term "GI-COVID."

Clinical Course of GI Manifestations

After SARS-CoV-2 exposure, adults most commonly present with respiratory symptoms, with GI symptoms reported in 10%-15% of cases. However, the overall incidence of GI involvement during SARS-CoV-2 infection varies according to age, with children more likely than adults to manifest intestinal symptoms.

There are also differences in incidence reported when comparing hospitalized with nonhospitalized individuals. In early reports from the onset of the COVID-19 pandemic, 11%-43% of hospitalized adult patients manifested GI symptoms. Of note, the presence of GI symptoms was associated with more severe disease and thus predictive of outcomes in those admitted to hospitals.

In a multicenter study that assessed pediatric inpatients with COVID-19, GI manifestations were present in 57% of patients and were the first manifestation in 14%. Adjusted by confounding factors, those with GI symptoms had a higher risk for pediatric intensive care unit (PICU) admission. Patients admitted to the PICU also had higher serum C-reactive protein and aspartate aminotransferase values.

Emerging Data on MIS-C

In previously healthy children and adolescents, the severe, life-threatening complication of multisystem inflammatory syndrome in children (MIS-C) may present 2-6 weeks after acute infection with SARS-CoV-2. MIS-C appears to be an immune activation syndrome and is presumed to be the delayed immunologic sequelae of mild/asymptomatic SARS-CoV-2 infection. This response manifests as hyperinflammation in conjunction with a peak in antibody production a few weeks later.

One report of 186 children with MIS-C in the United States noted that the involved organ system included the GI tract in 92%, followed by cardiovascular in 80%, hematologic in 76%, mucocutaneous in 74%, and respiratory in 70%. Affected children were hospitalized for a median of 7 days, with 80% requiring intensive care, 20% receiving mechanical ventilation, and 48% receiving vasoactive support; 2% died. In a similar study of patients hospitalized in New York City, 88% had GI symptoms (abdominal pain, vomiting, and/or diarrhea). A retrospective chart review of patients with MIS-C found that the majority had GI symptoms with any portion of the GI tract potentially involved, but ileal and colonic inflammation predominated.

Whittaker and colleagues described the clinical characteristics of children in eight hospitals in England who met criteria for MIS-C that were temporally associated with SARS-CoV-2. At presentation, all of the patients manifested fever and nonspecific GI symptoms, including vomiting (45%), abdominal pain (53%), and diarrhea (52%). During hospitalization, 50% developed shock with evidence of myocardial dysfunction.

Belay and colleagues described the clinical characteristics of a large cohort of patients with MIS-C that were reported to the US Centers for Disease Control and Prevention (CDC). Of 1733 patients identified, GI symptoms were reported in 53%-67%. Over half developed hypotension or shock and were admitted for intensive care. Younger children more frequently presented with abdominal pain in contrast with adolescents, who more frequently manifest respiratory symptoms.

In a multicenter retrospective study of Italian children with COVID-19 that was conducted from the onset of the pandemic to early 2021, GI symptoms were noted in 38%. These manifestations were mild and self-limiting, comparable to other viral intestinal infections. However, a subset of children (9.5%) had severe GI manifestations of MIS-C, defined as a medical and/or radiologic diagnosis of acute abdomen, appendicitis, intussusception, pancreatitis, abdominal fluid collection, or diffuse adenomesenteritis requiring surgical consultation. Overall, 42% of this group underwent surgery. The authors noted that the clinical presentation of abdominal pain, lymphopenia, and increased C-reactive protein and ferritin levels were associated with a nine to 30-fold increased probability of these severe sequelae. In addition, the severity of the GI manifestations was correlated with age (5-10 years: overall response [OR], 8.33; > 10 years: OR, 6.37). Again, the presence of GI symptoms was a harbinger of hospitalization and PICU admission.

Given that GI symptoms are a common presentation of MIS-C, its diagnosis may be delayed as clinicians first consider other GI/viral infections, inflammatory bowel disease, or Kawasaki disease. Prompt identification of GI involvement and awareness of the potential outcomes may guide the management and improve the outcome.

These studies provide a clear picture of the differential presenting features of COVID-19 and MIS-C. Although there may be other environmental/genetic factors that govern the incidence, impact, and manifestations, COVID's status as an ongoing pandemic gives these observations worldwide relevance. This is evident in a recent report documenting pronounced GI symptoms in African children with COVID-19.

It should be noted, however, that the published data cited here reflect the impact of the initial variants of SARS-CoV-2. The GI binding, effects, and aftermath of infection with the Delta and Omicron variants is not yet known.

Cause and Effect, or Simply Coincidental?

Some insight into MIS-C pathogenesis was provided by Yonker and colleagues in their analysis of biospecimens from 100 children: 19 with MIS-C, 26 with acute COVID-19, and 55 controls. They demonstrated that in children with MIS-C, the prolonged presence of SARS-CoV-2 in the GI tract led to the release of zonulin, a biomarker of intestinal permeability, with subsequent trafficking of SARS-CoV-2 antigens into the bloodstream, leading to hyperinflammation. They were then able to decrease plasma SARS-CoV-2 spike antigen levels and inflammatory markers, with resulting clinical improvement after administration of larazotide, a zonulin antagonist.

These observations regarding the potential mechanism and triggers of MIS-C may offer biomarkers for early detection and/or strategies for prevention and treatment of MIS-C.

Bottom Line

The GI tract is the target of an immune-mediated inflammatory response that is triggered by SARS-CoV-2, with MIS-C being the major manifestation of the resultant high degree of inflammation. These observations will allow an increased awareness of nonrespiratory symptoms of SARS-CoV-2 infection by clinicians working in emergency departments and primary care settings.

Clues that may enhance the ability of pediatric clinicians to recognize the potential for severe GI involvement include the occurrence of abdominal pain, leukopenia, and elevated inflammatory markers. Their presence should raise suspicion of MIS-C and lead to early evaluation.

Of note, COVID-19 mRNA vaccination is associated with a lower incidence of MIS-C in adolescents. This underscores the importance of COVID vaccination for all eligible children. Yet, we clearly have our work cut out for us. Of 107 children with MIS-C who were hospitalized in France, 31% were adolescents eligible for vaccination; however, none had been fully vaccinated. At the end of 2021, CDC data noted that less than 1% of vaccine-eligible children (12-17 years) were fully vaccinated.

The Pfizer-BioNTech vaccine is now authorized for receipt by children aged 5-11 years, the age group that is at highest risk for MIS-C. However, despite the approval of vaccines for these younger children, there is limited access in some parts of the United States at a time of rising incidence.

We look forward to broad availability of pediatric vaccination strategies. In addition, with the intense focus on safe and effective therapeutics for SARS-CoV-2 infection, we hope to soon have strategies to prevent and/or treat the life-threatening manifestations and long-term consequences of MIS-C. For example, the recently reported central role of the gut microbiota in immunity against SARS-CoV-2 infection offer the possibility that "microbiota modulation" may both reduce GI injury and enhance vaccine efficacy.

William F. Balistreri, MD, is the Dorothy M.M. Kersten Professor of Pediatrics; director emeritus, Pediatric Liver Care Center; medical director emeritus, liver transplantation; and professor, University of Cincinnati College of Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center. He has served as director of the Division of Gastroenterology, Hepatology and Nutrition at Cincinnati Children's for 25 years and frequently covers gastroenterology, liver, and nutrition-related topics for Medscape. Dr Balistreri is currently editor-in-chief of The Journal of Pediatrics, having previously served as editor-in-chief of several journals and textbooks. He also became the first pediatrician to act as president of the American Association for the Study of Liver Diseases. In his spare time, he coaches youth lacrosse.

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