Partial trisomy of the long arm of chromosome 1: prenatal diagnosis, clinical evaluation and cytogenetic findings. Case report and review of the literature.

Partial trisomy of the long arm of chromosome 1 is a relatively rare cytogenetic anomaly. Its phenotype has still not been completely defined, because of the cytogenetic heterogeneity of the cases so far described. We report a prenatal case of partial 1q trisomy associated with partial monosomy 4q, secondary to balanced maternal translocation t(1;4).

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.