Ring chromosome 4: Wolf syndrome and unspecific developmental anomalies.

A new case of ring chromosome 4 in a 18-month-old girl is described. The patient presented extreme growth failure, psychomotor retardation, and some features of 4p deletion or Wolf syndrome. No significant loss of genetic material could be seen by G-banding technique (breakpoints p16q35). The ring was found to be unstable both in lymphocyte and fibroblast culture and a substantial proportion of aneuploid cells containing derivatives of the ring could be observed. An increased cell death-rate could be detected by cell viability determination with trypan blue in the first subculture of skin fibroblasts. It is suggested that this finding is a consequence of behavioural instability of the ring at mitosis existing probably in vivo as well. The clinical and cytogenetic findings in this patient were compared with those in the other 16 cases with ring 4 published so far. It is suggested that the phenotype in patients with this chromosomal anomaly is a mixture of phenotypic abnormalities generated by both the chromosomal deletion prior to ring formation (features of Wolf syndrome) and the behavioural instability of the ring at mitosis (unspecific developmental anomalies).