title: Monozygotic twins discordant for trisomy 21 or chimeric dizygotic twins?
mesh_terms: D002678:Chimera; D004200:Diseases in Twins; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic