Dispermic chimerism with two abnormal cell lines, 47,XY, +21 and 47,XX, +12.

Chimerism in humans appears to be a rare phenomenon that is usually discovered by accident. Here we describe a stillborn male fetus with multiple congenital anomalies which was found to have two cytogenetically abnormal cell lines, 47,XY, +21 and 47, XX, +12. The difference in sex chromosome constitution between the cell lines indicated that the fetus had dispermic chimerism. To our knowledge, this is the first report of chimerism with two abnormal cell lines. Copyright 2001 Wiley-Liss, Inc.