Prenatal diagnosis of chromosomal abnormalities in fetuses with abnormal cardiac ultrasound findings: evaluation of chromosomal microarray-based analysis.

OBJECTIVES: To assess the frequency of karyotype abnormalities and chromosome 22q11.2 deletion syndrome among fetuses with abnormal cardiac ultrasound findings, and to evaluate the clinical value of chromosomal microarray-based analysis (CMA) in the study of such pregnancies. METHODS: First, we carried out retrospective analysis of karyotype abnormalities and 22q11.2 deletion syndrome cases diagnosed between January 2009 and December 2011 in our center among fetuses with abnormal cardiac ultrasound findings (n = 276). Second, CMA was performed in 51 of the fetuses with such findings, normal karyotype and negative or no 22q11.2 deletion syndrome study, and in the only fetus with a heart defect and an apparently balanced de novo chromosomal rearrangement. RESULTS: Out of the 276 pregnancies with abnormal cardiac ultrasound findings, karyotyping revealed a chromosomal abnormality in 44 (15.9%). Of fetuses with normal karyotype in which 22q11.2 deletion syndrome studies were performed, 6.4% (5/78) had this microdeletion syndrome. Among fetuses with abnormal cardiac findings, normal karyotype and negative or no 22q11.2 deletion syndrome study that underwent CMA, the detection rate of pathogenic copy number variants not detected by conventional cytogenetics was 2.0% (1/51), and no variants of uncertain clinical significance were found. In the fetus with a heart defect and an apparently balanced de novo chromosomal rearrangement, CMA revealed that the rearrangement was not truly balanced. CONCLUSIONS: In the assessment of genetic abnormalities in pregnancies with abnormal cardiac ultrasound findings, the diagnostic yield may be increased by 2% if CMA is used as a complementary tool to conventional cytogenetics. Our results suggest that CMA could be a good alternative to karyotyping in these pregnancies.

El diagnóstico citogenético prenatal aquí y ahora. Validez actual y futura del cariotipo / The cytogenetic prenatal diagnosis nowadays. Present and future value of karyotype

El cariotipo convencional obtenido mediante las técnicasde bandas es considerado como el gold standard deldiagnóstico prenatal citogenético; nos da la información detodos los cromosomas, es decir de todo el genoma, con un nivelde resolución limitado pero aceptable. Está incorporado en lapráctica asistencial de la mayoría de hospitales de tercer nivelde nuestro país, así como en centros sanitarios y laboratoriosprivados. En buena parte de ellos se aplican además otrastécnicas complementarias de citogenética molecular paracompletar algún diagnóstico concreto.Durante estos últimos años se han ido desarrollando técnicasmoleculares que permiten superar determinados inconvenientesdel cultivo celular y análisis citogenético, como laduración del cultivo (Quantitative Fluorescent PolymeraseChain Reaction [QF-PCR]) o el limitado poder de resolución delos cromosomas bandeados (técnicas de Array Genomic Hybridization[AGH]). Sin embargo, estas técnicas también tienensus desventajas con respecto al cariotipo: resultados parciales,coste económico elevado, falta de información de las reorganizacionescromosómicas (fundamental para el consejo genéticode la gestante y su familia), y problemas de interpretaciónde los resultados debido a la existencia de Copy Number Variants(CNV) polimórficas o benignas, con el agravante de contarsolamente con el examen ecográfico del «paciente».A corto plazo, por su relación coste-beneficio, el futurodel cariotipo como técnica básica de diagnóstico prenatalcitogenético parece asegurado. El empleo de técnicas complementariasmoleculares o citogenético-moleculares, paracompletar los análisis en los casos que lo requieran, va a sercada vez más necesario...(AU)

The conventional karyotype, obtained using bandingtechniques, is considered the «gold standard» in prenatal cytogeneticdiagnosis: it gives genome-wide information (from allthe chromosomes), with limited but acceptable resolution.Most of the great public hospitals of our country, as well asmany private sanitary centres and laboratories, offer conventionalkaryotype as routine prenatal diagnosis, and in most ofthem, complementary molecular-cytogenetic techniques arealso available for application in special cases.New molecular techniques have been developed duringthe last years, which overcome certain drawbacks of cellculture and cytogenetic analysis, such as the duration of theculture (Quantitative Fluorescent Polymerase Chain Reaction[QF-PCR]) or the limited resolution of the banded chromosomes(Array Genomic Hybridization [AGH] techniques).However, these techniques also have disadvantages with respectto the karyotype: partial results, high costs, lack of informationabout chromosome rearrangements (essential forthe genetic counselling to the pregnant woman and herfamily), and interpretation problems of results due to theexistence of benign Copy Number Variants (CNV) and difficultiesto correlate the findings with the fetal phenotype,only visible through echography.In the near future, the karyotype will remain as the basictool in cytogenetic prenatal diagnosis, due to its costbenefitrelation. The use of complementary molecular ormolecular-cytogenetic techniques in special cases will becomemore and more frequent.In the distant future, with the rising technological advances,the karyotype will probably become the complementary technique, but it will be also necessary in most casesfor validation (Fluorescence in Situ Hybridization [FISH])and, above all, as an essential tool for genetic counselling(AU)

Characterization of a 5.8-Mb interstitial deletion of chromosome 3p in a girl with 46,XX,inv(7)dn karyotype and phenotypic abnormalities.

Interstitial deletions of the short arm of chromosome 3 are rare, and a specific clinical phenotype has not been defined. We report the first isolated cryptic proximal interstitial 3p deletion, del(3)(p12.3p13), assessed by array-based comparative genomic hybridization in a girl with an inversion of chromosome 7, whose phenotype includes neurodevelopmental delay, growth retardation, dysmorphic facial features, hypophysis hypoplasia, gastroesophageal reflux, clinodactyly, preauricular appendix, and myopia. Her features are similar to those observed in the previously reported cases of proximal 3p deletions overlapping with our imbalance, indicating that her clinical manifestations are likely to be due to the deletion. As our patient's imbalance is the first non-cytogenetically visible proximal interstitial 3p deletion uncomplicated by other imbalances, its characterization has allowed us to narrow the minimal deletion interval associated with growth retardation and neurodevelopmental delay to the 3p12.3-p13 region. Among the genes found in this region, ROBO1, ROBO2, PDZRN3 and CNTN3 might play a role in the neurodevelopmental delay of the patient. This study provides additional evidence that cryptic imbalances anywhere along the genome can be found in patients with phenotypic abnormalities and a balanced chromosome rearrangement.