Patau syndrome with long survival in a case of unusual mosaic trisomy 13.

We report a 12-year-old patient with Patau syndrome, in whom two cell lines were present from birth, one with total trisomy 13 due to isochromosome (13q), and one with partial trisomy 13. A cytogenetic re-evaluation at 9 years of age brought to light in skin fibroblasts a third cell line, partially monosomic for chromosome 13. The derivatives (13) present in the three cell lines were characterized through fluorescence in situ hybridization (FISH) experiments with suitable probes; the results suggested a sequence of rearrangements which beginning from an isochromosome (13q) could have led to the other two derivatives. We report the clinical data at birth and at the age of 12; at this age pigmentary lesions with phylloid pattern were noted. Cytogenetic findings of the chromosomal analyses on different tissues, including skin fibroblasts from differently pigmented areas, are also reported.

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.