Trofinetide-Induced Enterocolitis Syndrome in a Child with Rett Syndrome.

Trofinetide, a synthetic analog of glycine-proline-glutamate (GPE), is the first food and drug administration-approved treatment for Rett syndrome. Gastrointestinal side effects (primarily diarrhea) are common, but severe immune-mediated reactions have not been described. We report a case of a young girl with genetically confirmed Rett syndrome who developed emesis, pallor, and lethargy after 2 months of treatment with trofinetide. An attempt was made to restart the medication after being held for a week, but the patient again experienced adverse symptoms and the drug was held. After 3 months without the medication, she experienced recurrence of initial symptoms within hours of rechallenge, consistent with food protein-induced enterocolitis syndrome (FPIES). The medication was not continued after the re-challenge. The concept of drug-induced enterocolitis syndrome (DIES) has been reported with other agents; however, to our knowledge, this represents the first reported case of FPIES/DIES triggered by trofinetide. This case expands the spectrum of trofinetide-related adverse reactions and emphasizes the need to distinguish immune-mediated enterocolitis from dose-dependent osmotic diarrhea and highlights the importance of clinician vigilance when initiating similar therapies in children with complex neurodevelopmental disorders.