Interstitial deletion 13q33 resulting from maternal insertional translocation.

A 32-month-old female with a unique interstitial deletion of 13q is presented, including cytogenetic and gene marker studies. The deleted 13 in the patient is a result of malsegregation of a maternal insertional translocation involving chromosomes 7 and 13, 46,XX,ins(7;13)(q22;q32q34). The demonstration of two esterase D alleles in this patient excludes band 13q33 as the site of the ESD locus, previously assigned to the distal long arm of chromosome 13. The BUdR dye studies reveal that the replicative pattern for 13q31 and 13q21 is not altered by deletion of 13q33 and permit precise delineation of the breakpoints of the rearrangement.