Case description of severe immune-related enteritis after in utero exposure to pembrolizumab

Immune checkpoint blockade has become standard treatment for many types of cancer. A 26-year old, nine-week pregnant woman in The Netherlands received a diagnosis of stage IIIB melanoma. After excision, adjuvant pembrolizumab was started at 16 weeks’ gestation. At 37 weeks’ gestation, which was 3 weeks after the last pembrolizumab dose, labor was induced. A healthy boy was born. At the age of 4 months, the child was referred to a hospital with a history of watery diarrhea and failure to thrive. Known causes of the symptoms were ruled out, and the diagnosis of pembrolizumab-induced immune-related gastroenterocolitis was supported by the results of histopathological assays, immunophenotyping, and analysis of the level of antibodies against PD-1. The infants condition was successfully treated with prednisolone and infliximab.