Pure partial trisomy of 6p12.1-p22.1 secondary to a familial 12/6 insertion in two malformed babies.

We describe two malformed infants with trisomy 6p12.1-p22.1 due to 12/6 interchromosomal insertion. The phenotypic data observed in these patients are compared chiefly with a case cytogenetically similar described by Villa et al. [A. Villa, E.G. Gomez, L. Rodriguez, R.H. Rastrollo, M.E. Martinez Tallo, M.L. Martinez-Frias, Interstitial tandem duplication of 6p: a case with partial trisomy (6)(p12p21.3), Am. J. Med. Genet. 90 (2000) 369-375]. All three infants are trisomic for a genomic segment which largely overlaps that reported as duplicated in previous cases, but with the addition of a more proximal segment, extending from 6p12 to 6p21. We suggest that some of their phenotypic anomalies are due to the trisomy of this chromosomal region. We also speculate on the possible role played by the TFAP2B (Transcription Factor AP2-beta) gene, which is one of the genes mapped on the duplicated segment.