In Reply.—I would like to point out that phenotypic differences between unrelated individuals with apparently identical chromosomal duplications can be due to three mechanisms: (1) differences in the extent of the duplicated segment; (2) differences in the associated deletions in cases of inherited reciprocal translocations; and (3) different genetic backgrounds.
Our patients with duplication of chromosome 2 (region 2p23→2pter) reported in the Journal presumably also have a minute deletion from the 7q terminus, as we have described and discussed in the article. This deletion is hypothetical since it is not evident on banded metaphase chromosomes, and meiotic studies to prove the reciprocal nature of the translocation have not been possible. Therefore, we did not include the deletion in the title. We believe that the designation of "duplication/deficiency syndrome" should be reserved for those cases in which the deficiency is cytologically evident, such as in unbalanced off-spring of carriers of