Two New Cases of D1 Trisomy in Man

WO cases of the D, trisomy syndrome have been reported to date PATAU, SMITH and DEMARS, 1961). In each case there were seven rather than six chromosomes of the D group (classification by PATAU, 1960) which contains the chromosomes 13-15 (PATAU'S as well as Denver system). Contrary claims notwithstanding, it is at present not possible to distinguish reliably between these chromosomes ( THERMAN et d., 1961). Nonetheless, it appears certain that in both cases the same chro-Iiiosome was present in triplicate, the clinical resemblance of the two patients being by far too great to admit of any other interpretation. THERMAN d cil. (1961) named the responsible chromosome D,, proposing that in general a suffix to the group symbol be used to denote a chromosome that is identified by the phenotype of a trisomic rather than cytologically.