Ring-18 and isopseudodicentric-18 in the same child: a hypothesis to account for common origin.

A child with two cell lines, one with a ring 18 and the other with an isodicentric 18 with a suppressed centromere is described. A hypothesis that could account for a common origin of the two cell lines is presented and discussed. The clinical features of this child were compatible with some of the features for each of the syndromes of 18p-, 18q-, and trisomy 18 as described in the literature.