De novo activating GUCY2C variant with prenatal bowel dilatation, neonatal functional obstruction, and reversible intestinal failure: A case report.

Background: Activating variants in GUCY2C increase cyclic GMP signaling in enterocytes, driving chloride rich luminal secretion and impaired sodium absorption. Affected neonates can present with prenatal bowel dilatation and severe postnatal fluid losses that mimic mechanical obstruction. Case report: We describe a term male infant with fetal ultrasound and MRI evidence of markedly dilated bowel loops and severe polyhydramnios. Fetal testing identified a de novo heterozygous GUCY2C missense variant (c.2732 A>G). After birth, profuse intestinal secretion combined with profound intestinal hypotonia led to acute functional obstruction and massive ileal dilatation, prompting urgent laparotomy and diverting ileostomy. No mechanical stenosis was found; the ileocecal valve and colon were patent. Histology showed eosinophilic enteritis with prominent ganglionitis and preserved ganglion cells. The infant required prolonged parenteral nutrition with gradual advancement of enteral feeds and fecal recycling through the distal mucous fistula to achieve enteral autonomy by 2 years of age. He is currently 3 years old. Conclusion: GUCY2C mediated secretory diarrhea may be complicated by severe dysmotility and inflammatory enteric neuropathy, requiring early decompression and prolonged intestinal rehabilitation before recovery.