Duplication of the Miller-Dieker Critical Region in a Patient with a Subtelomeric Unbalanced Translocation t(10;17)(p15.3;p13.3)

A new case of 17p13.3p13.1 microduplication resulted from unbalanced translocation: clinical and molecular cytogenetic characterization

Copy number gain 17 p13.3p13.1 was detected by chromosomal microarray (CMA) in a girl with developmental/speech delay and facial dysmorphism. FISH studies made it possible to establish that the identified genomic imbalance is the unbalanced t(9;17) translocation of maternal origin. Clinical features of the patient are also discussed. The advisability of using the combination of CMA and FISH analysis is shown. Copy number gains detected by clinical CMA should be confirmed using FISH analysis in order to determine the physical location of the duplicated segment. Parental follow-up studies is an important step to determine the origin of genomic imbalance. This approach not only allows a most comprehensive characterization of an identified chromosomal/genomic imbalance but also provision of an adequate medical and genetic counseling for a family taking into account a balanced chromosomal rearrangement.

Jacobsen syndrome and neonatal bleeding: report on two unrelated patients

Introduction

In 1973, Petrea Jacobsen described the first patient showing dysmorphic features, developmental delay and congenital heart disease (atrial and ventricular septal defect) associated to a 11q deletion, inherited from the father. Since then, more than 200 patients have been reported, and the chromosomal critical region responsible for this contiguous gene disorder has been identified.

Patients’ presentation

We report on two unrelated newborns observed in Italy affected by Jacobsen syndrome (JBS, also known as 11q23 deletion). Both patients presented prenatal and postnatal bleeding, growth and developmental delay, craniofacial dysmorphisms, multiple congenital anomalies, and pancytopenia of variable degree. Array comparative genomic hybridization (aCGH) identified a terminal deletion at 11q24.1-q25 of 12.5 Mb and 11 Mb, in Patient 1 and 2, respectively. Fluorescent in situ hybridization (FISH) analysis of the parents documented a de novo origin of the deletion for Patient 1; parents of Patient 2 refused further genetic investigations.

Conclusions

Present newborns show the full phenotype of JBS including thrombocytopenia, according to their wide 11q deletion size. Bleeding was particularly severe in one of them, leading to a cerebral hemorrhage. Our report highlights the relevance of early diagnosis, genetic counselling and careful management and follow-up of JBS patients, which may avoid severe clinical consequences and lower the mortality risk. It may provide further insights and a better characterization of JBS, suggesting new elements of the genotype-phenotype correlations.

Neuronal migration genes and a familial translocation t (3;17): candidate genes implicated in the phenotype

BACKGROUND

While Miller-Dieker syndrome critical region deletions are well known delineated anomalies, submicroscopic duplications in this region have recently emerged as a new distinctive syndrome. So far, only few cases have been described overlapping 17p13.3 duplications.

METHODS

In this study, we report on clinical and cytogenetic characterization of two new cases involving 17p13.3 and 3p26 chromosomal regions in two sisters with familial history of lissencephaly. Fluorescent In Situ Hybridization and array Comparative Genomic Hybridization were performed.

RESULTS

A deletion including the critical region of the Miller-Dieker syndrome of at least 2,9 Mb and a duplication of at least 3,6 Mb on the short arm of chromosome 3 were highlighted in one case. The opposite rearrangements, 17p13.3 duplication and 3p deletion, were observed in the second case. This double chromosomal aberration is the result of an adjacent 1:1 meiotic segregation of a maternal reciprocal translocation t(3,17)(p26.2;p13.3).

CONCLUSIONS

17p13.3 and 3p26 deletions have a clear range of phenotypic features while duplications still have an uncertain clinical significance. However, we could suggest that regardless of the type of the rearrangement, the gene dosage and interactions of CNTN4, CNTN6 and CHL1 in the 3p26 and PAFAH1B1, YWHAE in 17p13.3 could result in different clinical spectrums.

A cryptic balanced translocation (5;17), a puzzle revealed through a critical evaluation of the pedigree and a FISH focused on candidate loci suggested by the phenotype

We report a case of a woman with a cryptic balanced translocation between chromosomes 5 and 17, suspected during genetic counseling. The woman had a history of previous fetal losses attributed to lissencephaly and intra uterine growth retardation (IUGR) and a daughter with dysmorphic features and mental retardation, previously attributed to a small deletion 5pter, detected years ago by a first generation CGH-array. This peculiar combination of personal and family history suggested the opportunity to carry out a FISH approach, focusing on chromosomes 5 and 17, based on the idea that a malsegregation secondary to a balanced translocation, might have escaped the first CGH array. This approach allowed the identification of a balanced translocation in the mother, FISH in the affected child confirmed the partial 5p deletion predicted by the previous CGH array and identified a new 17p duplication that had not been detected before. The described translocation opens the possibility of alternative imbalances that were probably responsible for previous fetal losses. The imbalances were confirmed by a new high resolution SNP array. We conclude that despite the availability of highly effective and sensitive genomic approaches a careful evaluation of medical history is highly recommended since it can suggest clinical hypothesis that can be confirmed by more classical and molecular cytogenetic based approaches.