Ring chromosome 18 in a patient with multiple anomalies.

Ring chromosomes, long of interest in cytogenetics, have been intensively studied in corn and Drosophila (McClintock, 1932, 1938; Morgan, 1933; Battacharya, 1950) and also described in Crepis, Tulipa, Tradescantia, and other species. In the past few years, a number of reports of ring chromosomes in man have appeared (Table I). We recently encountered a mentally retarded patient with multiple congenital anomalies, in a high proportion of whose cells we found a ring chromosome 18. The clinical expression of patients with 18 long (Lejeune, Berger, Lafourcade, and Rethore, 1966) and short arm deletions (Grouchy, Bonnette, and Salmon, 1966) are contrasted and compared with the findings in our patient and other patients with ring 18 chromosomes. The variability in size and frequency of ring chromosomes in human subjects and in this patient are discussed.