A rare case of mosaic Down syndrome 46,XY/46,XY, -21, +i(21q)

Detailed studies were carried out on a patient with a rare type of mosaicism which gave rise to an effective 21 trisomy. The clinical signs of Down syndrome were minimal. The cytogenetic interpretation is that the abnormal clone had an isochromosome derived from a maternal No. 21. The normal cell line appears to be replacing the abnormal clone.