Severe Immune-Related Enteritis after In Utero Exposure to Pembrolizumab

This case report describes severe immune-related gastroenterocolitis in a 4 month old infant following in utero exposure to pembrolizumab, an anti-PD-1 monoclonal antibody used for maternal treatment of advanced-stage melanoma. The infant presented with intractable diarrhea, failure to thrive, and hypoalbuminemia. Histopathological analysis revealed villous atrophy and chronic inflammation resembling immune-related gastrointestinal toxicity seen in adults. Immunophenotyping showed hyperactivated T cells with elevated PD-1 and HLA-DR expression. The infant was successfully treated with prednisolone and infliximab. The case highlights the potential for delayed immune related adverse events in neonates exposed to immune checkpoint inhibitors during pregnancy, emphasizing the need for caution and postnatal monitoring.

This case report describes severe immune-related gastroenterocolitis in a 4 month old infant following in utero exposure to pembrolizumab, an anti-PD-1 monoclonal antibody used for maternal treatment of advanced-stage melanoma. The infant presented with intractable diarrhea, failure to thrive, and hypoalbuminemia. Histopathological analysis revealed villous atrophy and chronic inflammation resembling immune-related gastrointestinal toxicity seen in adults. Immunophenotyping showed hyperactivated T cells with elevated PD-1 and HLA-DR expression. The infant was successfully treated with prednisolone and infliximab. The case highlights the potential for delayed immune related adverse events in neonates exposed to immune checkpoint inhibitors during pregnancy, emphasizing the need for caution and postnatal monitoring.