INTERSTITIAL DELETION 5P ACCOMPANIED BY DICENTRIC RING FORMATION OF THE DELETED SEGMENT RESULTING IN TRISOMY 5P13-CEN

Karyotypes with an interstitial deletion and a marker chromosome forme d from the deleted segment are rare. We identified such a rearrangemen t in a newborn infant, who presented with macrocephaly, asymmetric squ are skull, minor facial anomalies, omphalocele, inguinal hernias, hypo spadias, and club feet. The karyotype 46,XY,del(5) (pter-->p13::cen--> qter)/47,X+dicr(5)(:p13--> cen::p13-->cen), del(5)(pter-->p13::cen-->q ter) was identified by banding studies and FISH analysis in the periph eral lymphocytes. One breakpoint on the del(5) maps distal to GDNF, an d FISH analysis using an alpha-satellite probe suggests that the proxi mal breakpoint maps within the centromere. The dicentric r(5) consists of two copies of the segment deleted in the del(5), resulting in tris omy of proximal 5p (5p13-cen). The phenotype of the propositus is comp ared with other trisomy 5p cases and possible mechanisms for the gener ation of this unique chromosomal rearrangement are discussed. (C) 1996 Wiley-Liss, Inc.