Reproduction in a female patient with Down's syndrome. Case report of a 46, XY child showing slight phenotypical anomalies, born to a 47, XX, + 21 mother.

A non-mongoloid boy born to a mongoloid mother is described. He showed aplasia of the left 5th finger and some clinical and dermatoglyphic features frequently found in Down's syndrome. Chromosome analysis revealed few hyperdiploid but no G-trisomic cells. An undetected G-trisomy mosaic, or a mechanism of extrachromosomal inheritance, and an embryonic development in a pathological milieu are discussed.