Microarray analysis of an unbalanced t(4;13) translocation narrows down the trisomy 13 associated polydactyly to a 7 Mb region.

摘要

We report here on our recent finding of a new patient with a cryptic chromosomal translocation and its associated clinical features. Our patient was a newborn male with hypertelorism, wide flat nasal bridge, cleft lip, and palate, as well as bilateral postaxial polydactyly of the hands. Initial karyotype analysis showed a terminal deletion of 4pl5.2 (Fig. 1a), consistent with a clinical diagnosis of Wolf-Hirschhorn syndrome. The presentation of postaxial polydactyly, which is unusual for the Wolf-Hirschhorn syndrome, prompted fluorescence in-situ hybridization (FISH) investigation to rule out a cryptic translocation. Considering that postaxial polydactyly has been observed in approximately 75% of trisomy 13 cases [Lewandowski and Yunis, 1977], we used a 13q specific sub-telomeric probe for the detection of possible partial trisomy 13q that was undetectable by conventional karyotype analysis. Indeed, the 13q probe showed an unbalanced 4;13 translocation, with monosomy for 4p15.2 and trisomy for 13q34 (Fig. 1b). This boy was born to a healthy teenage mother with a normal karyotype. His father was not available.