Since recognition of the autosomal trisomy D1 syndrome by Patau et al,1 120 cases with cytological confirmation have been reported. In two surveys, the observers have attempted to estimate the frequency of this syndrome by identification of all cases occurring within an area during a period of time. Neither of these reports emphasized either the frequency or the variability of arrangements of the D chromosomes.
In their study of York County, Ontario, from 1962 through 1965, Conen and Erkman2 ascertained nine cases of the D1 syndrome; four of the nine had D/D translocation, while the other five had 47 chromosomes. The area in England surveyed by Taylor3 was less precisely defined. She ascertained 27 cases during a period of five years, but four patients did not have the extra D chromosomal material usually considered necessary to confirm the diagnosis. Among the remaining 23 cases, three were due