[Ring chromosome 4 in twins].
A case of ring chromosome 4 in an eleven months old male child with severe mental retardation, microcephaly and craniofacial anomalies is described. The karyotype was: 46,XY, r(4) p16----q35). The patient shows only few elements of the Wolf syndrome, whose phenotype is observed in most of the other cases with analogue karyotype.