Subtelomeric rearrangements as neutral genomic polymorphisms.

Submicroscopic chromosomal rearrangements affecting telomeres are important aetiological contributors to the development of mental retardation. Results from over 2,500 analysed patients with mental retardation demonstrated that about 5% have a subtelomeric aberration. However, some subtelomeric rearrangements have no phenotypic consequences. Due to the heterogeneity of such rearrangements and to the limited information about which monosomy or trisomy can be tolerated without phenotypic effect, conclusions about the association of a specific aberration and the phenotypical consequences are often hard to draw. We performed a study of subtelomeric aberrations with the aim to provide more insights into the understanding of such rearrangements as neutral genomic polymorphisms. We found two new polymorphisms: a duplication or triplication of the subtelomeric region of the long arm of chromosome 4 and a trisomy of the subtelomeric region of the short arm of chromosome 6 owing to a transposition to chromosome 22. These new data are presented and discussed in the context of the published literature.

Association of deletions of the chromosomal region 15q24-ter and diaphragmatic hernia: a new case and discussion of the literature.

OBJECTIVE: To provide new insights into how chromosomal aberrations affect fetal development, as well as for the counseling of parents in comparable situations, it is important to characterize and report the genotypes of fetuses with clinical anomalies. METHODS: Molecular cytogenetic analyses in a fetus with congenital diaphragmatic hernia (CDH). RESULTS: This report describes the first case of a deletion of the region q26.1-ter on chromosome 15 occurring as a de novo event associated with CDH. A detailed review of the literature provides further evidence of a functional association between deletions within the chromosomal region 15q24-ter and the development of CDH. CONCLUSIONS: The obtained data argue that detection of such a deletion in the region 15q24-ter associated with CDH likely predicts a poor prognosis. This report highlights the importance of giving special diagnostic attention to the chromosomal region 15q24-ter when prenatal ultrasound examination provides evidence of a CDH and warrants further research to identify genetic elements within the chromosomal region 15q24-ter related to the development of diaphragmatic hernia.

Prenatal diagnosis of tetrasomy 9p with Dandy-Walker malformation.

OBJECTIVES: To add to the knowledge of chromosomal abnormalities associated with Dandy-Walker malformation. METHODS: Molecular cytogenetic analyses of a chorionic villus sampling and of an amniocentesis of a fetus with Dandy-Walker malformation and abnormal somatic development. RESULTS: All cells examined showed a 47, XY, +idic(9p)(pter-->q12::q12-->pter) de novo karyotype. This report describes the fourth case of a tetrasomy 9p associated with Dandy-Walker malformation. CONCLUSIONS: This case, together with the three previously reported cases of an association with a tetrasomy 9p, indicate that this chromosomal aberration should be looked for when Dandy-Walker malformation is detected via prenatal ultrasonography.

Patient with partial trisomy 9q and learning disability but no pyloric stenosis.

Partial trisomy of the long arm of chromosome 9 represents a very rare and heterogeneous group of chromosomal aberrations. Associated clinical features include learning disability and pyloric stenosis. We present the first patient to be reported with a duplication of the chromosome region 9q22.1-->q33. The patient (female, age 17 years) presented with growth retardation, microcephaly, facial dysmorphia, oesophageal atresia, aortic stenosis, ventricular septal defect, atrial septal defect II, hypothyroidism, and learning disability, but no pyloric stenosis. A review of all cases of partial trisomy 9q reported in the literature demonstrates that learning disability is a characteristic feature of this group of chromosomal aberrations. However, there are cases of duplications of the same chromosome 9 material, with and without pyloric stenosis. This study provides new information for future genetic counselling, especially in cases of prenatal diagnosis of partial trisomy 9q.

A fetus with trisomy 9p and trisomy 10p originating from unbalanced segregation of a maternal complex chromosome rearrangement t(4;10;9).

Complex chromosome rearrangements are only rarely seen in constitutional karyotypes. A case of prenatally detected trisomy 9p with trisomy 10p originating from adjacent segregation of a maternal complex chromosome rearrangement is reported. Ultrasound examination at 18 weeks of gestation showed cleft lip palate, club feet, structural anomalies of the cerebellum and cystic kidneys. Cytogenetic analysis of amnion cells revealed a female fetus with 47,XX,+der(9). FISH analyses together with parental karyotyping demonstrated the fetal additional chromosome to originate from malsegregation of a maternal complex chromosomal rearrangement. The mother is carrier of a balanced translocation t(4;10;9) (q12; p11;q13). Postmortem examination of the fetus showed nose anomalies, cleft lip palate, low set ears, club feet, lung anomalies, cystic kidney and aplasia of the uterus. Reporting of such rare cases is important in order to enable this information to be used for genetic counselling in similar situations.