PRENATAL-DIAGNOSIS OF A HALF-CRYPTIC TRANSLOCATION USING CHROMOSOME MICRODISSECTION

This report describes a case of a paternal balanced, but apparently no n-reciprocal, insertion of chromosome 15 material into the short arm o f chromosome 17 with difficulties in distinguishing between the normal and the deleted chromosome 15 in prenatal karyotype analysis. Microdi ssection and degenerate oligonucleotide-primed polymerase chain reacti on (DOP-PCR) of the paternal 17p+ chromosome was performed to generate a painting probe specific for the small legion inserted from chromoso me 15 into chromosome 17. Fluorescence ill situ hybridization (FISH) o f this probe simultaneously with a differentially labelled 15q microdi ssection probe enabled the identification of a balanced karyotype in t he fetus, In this case, microdissection combined with FISH was the onl y method for obtaining a reliable result within the short time availab le for prenatal diagnosis. In addition, it was possible to identify wi th certainty the originally suspected reciprocal translocation as an i nsertion of the region 15q22.3-->q23 or 24 into the sub-telomeric regi on of 17p [ins(17;15)(p13;q22.3q23 or 24)]. Thus, the chromosomal defe ct of two family members with a partial trisomy of chromosome 15 havin g severe mental retardation and dysmorphic features was identified pre cisely. (C) 1997 by John Wiley & Sons, Ltd.