A human ring D chromosome associated with multiple congenital abnormalities.

239 sulted in 2 normal living children. The 3rd pregnancy resulted in a spontaneous abortion. Her last pregnancy at the age of 29 years resulted in a child with Down's syndrome. The child had 47 chromosomes with trisomy 21. The patient also has 47 chromosomes with a triple X karyotype. About 200% of her buccal cells contain 2 chromatin bodies. The patient's husband is physically and mentally normal. He has 46 chromosomes with a normal XY karyotype. Discussion Triple X females have shown a marked pheno-typic variability. It is this variability of the physical findings that has made screening for these females difficult without examining their buccal cells for 2 chromatin bodies or doing a chromosome evaluation. The present triple X female was drawn to our attention after she gave birth to a child with Down's syndrome. There was nothing about this woman's physical appearance that would have indicated that she possessed an extra X chromosome. While many of the reported patients with the triple X syndrome have had reduced intelligence, this finding is probably due to a biased selection of patients (Day et al, 1964). Many of the initial reports about these females came from institutions for the mentally retarded where mass screening was performed. Our patient is one of the few observed with normal intelligence; however, it is suspected that there are many more like her in the general population. Incidence at birth of this trisomic state is between 1-4 and 1-8 per 1000 live births (Maclean, Harnden, and Court Brown, 1961). Such a high frequency of this trisomic condition would indicate that there are many more triple X females in the general population than can be accounted for in institutions for the mentally retarded. To our knowledge this is the first example of a triple X female giving birth to a child with a chro-mosomal abnormality. While a number of triple X females have given birth, the offspring have been chromosomally normal. It is not possible to determine if this triple X mother was at an increased risk of giving birth to a child with Down's syndrome. Examples of 2 chromosomal abnormalities in the same individual are well documented (Smith, 1970). There is, however, a lack of information about females with chromosomal abnormalities being at risk to produce an entirely different chromosome abnormality since most of these individuals are physically or mentally handicapped or fail to procreate. …