Reproductive outcome in 3 families with a satellited chromosome 4 with review of the literature.

We describe 3 families segregating for a translocation of the nucleolus organizer region (NOR) onto chromosome 4. Review of previously reported cases of translocations involving NOR and chromosome 4 shows that these translocations may be associated with variable reproductive outcomes. We provide evidence that imprinting is not the mechanism responsible for the variable reproductive outcomes in the case of satellited 4p chromosomes; this may offer indirect support for a ribosomal gene position effect. Translocated ribosomal genes may influence the expression of neighboring genes and could explain the variable phenotypes in individuals with satellited nonacrocentric chromosomes. We recommend that prenatal counseling of individuals with satellited nonacrocentric chromosomes should be cautious.