Giant omphalocele and "prune belly" sequence as components of the Beckwith-Wiedemann syndrome.

We report a case of severe Beckwith-Wiedemann syndrome (BWS) in a fetus at 16 weeks of gestation. This presentation, incompatible with life, included a giant omphalocele and absence of abdominal wall musculature with extremely dilated bladder, as in the "prune belly" sequence. Adrenal cytomegaly pointed to BWS. Molecular analysis confirmed the diagnosis of BWS and showed an isolated demethylation of the KCNQ1OT1 gene. This report demonstrates that lethal fetal abdominal wall defects associated with adrenal cytomegaly are linked to epigenetic change of the 11p15 imprinted region.