Further studies on the genetic heterogeneity of cebocephaly.

The detailed morphological description of 4 cases with cebocephaly, 3 of which were karotyped (one with D trisomy and 2 with normal karyotypes), are presented. Analysis of all cytogenetically studied cases with this malformation reveals that cebocephaly with a normal karyotype may result from more than one mutant gene, and so it may be accompanied by different extracranial abnormalities. On the other hand an absence of visceral malformations does not exclude chromosomal aberrations; thus 18p- syndrome, where cebocephaly is frequent, may have no visceral abnormalities.