Trisomy 4p: five new observations and overview.

Five new cases of trisomy of the short arm of chromosome No. 4 are presented. In two brothers the abnormality arose from segregation of the 4p chromosome present in the mother who is a carrier of a centric fission of one No. 4 chromosome. In the other three patients, the chromosome imbalance originated from segregation of a balanced maternal 3p/4q or 4/22 translocation. The available data, derived from the 4p trisomics reported so far, are adequate to establish trisomy of the short arm of chromosome No. 4 as a definite clinical entity. The most outstanding findings include growth retardation of prenatal onset, severe mental deficiency, microcephaly and a peculiar constellation of facial dysmorphisms. The dermatoglyphic patterns and the radiological findings may help towards a correct interpretation of the syndrome.