A deleted B chromosome in a mosaic mother and her cri du chat progeny.

Familial occurrence of chromosomal anomalies may be caused by: (1) numerical chromosomal abnormalities present in all or some of the cells of one of the parents (secondary non-disjunction), or (2) by a genetically determined tendency to meiotic or mitotic non-disjunction. Structural chromosomal abnormalities such as translocations have also been described as frequent causes of familial chromosomal errors. It is the purpose of this paper to report the results of chromosome studies in a family in which two sibs carried a deletion of a short arm of a chromosome No. 5. One was a child with the typical cri du chat syndrome , the other was a fetus weighing 14 g. The mother was found to be a mosaic of normal cells and cells with a deleted B chromosome. A fertile mosaic of this type has not been reported before. Material and Methods Chromosomal analysis was carried out on cells from peripheral blood of a child with the cri du chat syndrome. Later the mother, her two living children, and a fetus, four of her five sibs, the maternal grandmother, and the father of the child with the cri du chat syndrome were also investigated (Fig. 1). The maternal grandfather and one of the mother's sibs were dead at the time of the investigations. A modification of the method of Moorhead et al. (1960) was used. Other tissues were investigated by a modification of the method of Harnden (1960) (Philip, 1967). Autoradio-graphic studies were performed by the method of Froland (1965). Case Reports The Mother. The mother was 33 years old and unmarried , and the father was 30, when the child with the cri du chat syndrome was born. General and gynae-cological examination of the mother, who had always enjoyed good health, showed normal findings. With her first concubinary she had four pregnancies, one ending as a spontaneous abortion, one was legally interrupted, and two resulted in normal children. With her second concubinary she became pregnant twice; the first of these pregnancies resulted in the propositus with the cri du chat syndrome, the second was terminated by hysterotomy at four months' gestational age. At operation the internal genitalia were found to be normal, and biopsies from the following organs were removed from the mother for chromosomal analysis: skin, muscle, uterus, and right and left ovary. The fetus was dissected with the help of a dissecting microscope, removing tissues from skin, …