Fulminant necrotizing enterocolitis associated with severe RSV infection in a preterm infant following Nirsevimab prophylaxis: a case report.

Respiratory syncytial virus (RSV) prophylaxis with the monoclonal antibody Nirsevimab has shown high efficacy in preventing severe lower respiratory tract infections in infants. However, the sequences of immunopathological phenomena leading to breakthrough infections and the role of RSV in causing extrapulmonary disease remain poorly understood. We report on a former preterm infant who developed an unusually severe form of necrotizing enterocolitis (NEC) requiring multiple emergency laparotomies and prolonged intensive care treatment in the context of severe RSV-bronchiolitis 22 days after passive immunization with Nirsevimab. RSV RNA was retrospectively detected using a validated RSV PCR assay in resected intestinal tissue obtained during the acute disease phase but was not detected in tissue collected during later surgical reconstruction. Our case highlights the need for clinicians to maintain a high index of suspicion for intestinal complications in infants with severe RSV infection. Although these findings raise the possibility of intestinal RSV involvement, a causal relationship between Nirsevimab prophylaxis, antibody-dependent enhancement (ADE), and NEC cannot be established from this single case. Confirmation in additional clinical and translational studies is required. Further clinical and translational studies are required to clarify the potential role of RSV in intestinal disease and the mechanisms underlying severe breakthrough infections.