In Utero Per- and Polyfluoroalkyl Substances (PFAS) Exposure and Changes in Infant T Helper Cell Development among UPSIDE-ECHO Cohort Participants.

Megacystis–microcolon–intestinal hypoperistalsis syndrome (MMIHS) is a rare congenital disorder characterized by severe impairment of smooth muscle function involving both the gastrointestinal and urinary systems. It is defined by the triad of megacystis without mechanical obstruction, microcolon, and intestinal hypoperistalsis . Pathogenic variants in the gene, encoding γ-2 smooth muscle actin, represent the most common genetic cause. These mutations impair smooth muscle contractility, leading to intestinal dysmotility and bladder dysfunction , . Prenatal detection of fetal megacystis may raise suspicion of MMIHS. After birth, affected neonates typically present with abdominal distension, feeding intolerance, and failure to establish effective intestinal transit, frequently evolving into intestinal failure .