[Pericentric inversion of the Y chromosome as an exclusion constellation]

A 37 year old second gravida received amniocentesis, because of advanced maternal age. Cytogenetic investigations of the fetal cells revealed a male karyotype with a pericentric inversion of the Y chromosome. Chromosome analysis of the father was also undertaken in order to decide whether this inversion was inherited or of de novo origin. The results of cytogenetic examinations of the mother as well as of two alleged fathers enabled us to detect an exclusion of paternity for one man and a positive hint of paternity for the other. The cytogenetic markers used were the inversion itself and a high Q-fluorescence intensity in one homologue of chromosome 13. The results show that the analysis of chromosomal polymorphisms may offer a suitable tool to avoid false interpretations concerning the origin of structural chromosome abnormalities in prenatal diagnosis (inherited or de novo).