Multicolor banding remains an important adjunct to array CGH and conventional karyotyping

Interphase Chromosome Profiling: A Method for Conventional Banded Chromosome Analysis Using Interphase Nuclei

CONTEXT

- Chromosome analysis on bone marrow or peripheral blood samples fails in a small proportion of attempts. A method that is more reliable, with similar or better resolution, would be a welcome addition to the armamentarium of the cytogenetics laboratory.

OBJECTIVE

- To develop a method similar to banded metaphase chromosome analysis that relies only on interphase nuclei.

DESIGN

- To label multiple targets in an equidistant fashion along the entire length of each chromosome, including landmark subtelomere and centromere regions. Each label so generated by using cloned bacterial artificial chromosome probes is molecularly distinct with unique spectral characteristics, so the number and position of the labels can be tracked to identify chromosome abnormalities.

RESULTS

- Interphase chromosome profiling (ICP) demonstrated results similar to conventional chromosome analysis and fluorescence in situ hybridization in 55 previously studied cases and obtained useful ICP chromosome analysis results on another 29 cases in which conventional methods failed.

CONCLUSIONS

- ICP is a new and powerful method to karyotype peripheral blood and bone marrow aspirate preparations without reliance on metaphase chromosome preparations. It will be of particular value for cases with a failed conventional analysis or when a fast turnaround time is required.

Pallister-Killian syndrome: Cytogenetics and molecular investigations of mosaic tetrasomy 12p in prenatal chorionic villus and in amniocytes. Strategy of prenatal diagnosis

OBJECTIVE

Pallister-Killian syndrome (PKS) is a rare, sporadic genetic disorder caused by mosaic tetrasomy of the short arm of chromosome 12 (12p). Clinically, PKS is characterized by several systemic abnormalities, such as intellectual impairment, hearing loss, epilepsy, hypotonia, craniofacial dysmorphism, pigmentary skin anomalies, epilepsy, and a variety of congenital malformations. Prenatally, PKS can be suspected in the presence of ultrasound anomalies: diaphragmatic hernia, rhizomelic micromelia, hydrops fetalis, fetal overweight, ventriculomegaly in the central nervous system, congenital heart defects, or absent visualization of the stomach. In all these cases, a detailed genetic study is required. PKS is diagnosed by prenatal genetic analysis through chorionic villus sampling, genetic amniocentesis, and cordocentesis.

CASE REPORT

We report two cases of PKS with prenatal diagnosis of isochromosome 12p made by cytogenetic studies. The first case is of a 36-year-old pregnant woman who underwent genetic chorionic villus sampling at 13^th weeks of gestation after 1^st trimester prenatal ultrasound revealed clinical features of PKS: flat nasal bridge and fetal hydrops. The second case is of a 32-year-old pregnant woman with genetic amniocentesis at 17^th weeks of gestation that showed mos46,XX[21]/47,XX,+i(12p) associated to PKS.

CONCLUSION

New molecular cytogenetic techniques array comparative genomic hybridization and fluorescence in-situ hybridization in association with conventional karyotype are pivotal innovative tools to search for chromosomic anomalies and for a complete prenatal diagnosis, especially in cases such as PKS where array comparative genomic hybridization analysis alone could not show mosaicism of i(12p).