Nuchal cysts syndromes: etiology, pathogenesis, and prenatal diagnosis.

We examined 10 fetuses with nuchal cysts and compared the findings with 32 cases from the literature. Based on their characteristics, we propose that nuchal cysts are signs of four causally and pathogenetically different entities: cystic nuchal blebs present in otherwise normal fetuses as a postmortem change; 45,X fetuses who have a particular appearance and multiple congenital malformations; an apparently autosomal recessive syndrome of multiple cysts (that extend into deep muscular planes), generalized edema, cleft palate, peculiar skeletal characteristics, acutely angulated ribs (producing a bell-shaped rib cage), and shortened long bones; and in fetuses with syndromes that are inherited (multiple pterygium, Roberts) and chromosomal (trisomy 13, trisomy 21) as an unspecific sign representing both primary and secondary lesions.