Eva Pompilii

Mowat–Wilson syndrome: Facial phenotype changing with age: Study of 19 Italian patients and review of the literature

Mowat–Wilson syndrome (MWS; OMIM #235730) is a genetic condition caused by heterozygous mutations or deletions of the ZEB2 gene, and characterized by typical face, moderate‐to‐severe mental retardation, epilepsy, Hirschsprung disease, and multiple congenital anomalies, including genital anomalies (particularly hypospadias in males), congenital heart defects, agenesis of the corpus callosum, and eye defects. Since the first delineation by Mowat et al. [Mowat et al. ( 1998 ); J Med Genet 35:617–623], ∼179 patients with ZEB2 mutations, deletions or cytogenetic abnormalities have been reported primarily from Europe, Australia and the United States. Genetic defects include chromosome 2q21–q23 microdeletions (or different chromosome rearrangements) in few patients, and ZEB2 mutations in most. We report on clinical and genetic data from 19 Italian patients, diagnosed within the last 5 years, including six previously published, and compare them with patients already reported. The main purpose of this review is to underline a highly consistent phenotype and to highlight the phenotypic evolution occurring with age, particularly of the facial characteristics. The prevalence of MWS is likely to be underestimated. Knowledge of the phenotypic spectrum of MWS and of its changing phenotype with age can improve the detection rate of this condition.

Interpreting mosaicism in chorionic villi: results of a monocentric series of 1001 mosaics in chorionic villi with follow‐up amniocentesis

Chromosomal mosaicism in chorionic villi (CV) is detected in ~1–2% of cases. When a mosaic in CV is detected during prenatal diagnosis, a confirmatory karyotype should be performed on amniocytes to discriminate between a mosaic confined to the placenta [confined placental mosaicism (CPM)] and one generalized to the fetus [true fetal mosaicism (TFM)]. We determined the likelihood that any mosaic abnormalities identified through CV samples are confirmed in the fetus.

The type of feto‐placental aneuploidy detected by cfDNA testing may influence the choice of confirmatory diagnostic procedure

Cell‐free DNA (cfDNA) screening can provide false positive/negative results because the fetal fraction originates primarily from trophoblast. Consequently, invasive diagnostic testing is recommended to confirm a high‐risk result. Currently, there is debate about the most appropriate invasive method. We sought to estimate the frequency in which a chorionic villus sampling (CVS) performed after a high‐risk cfDNA result would require a follow‐up amniocentesis due to placental mosaicism.

Autosomal recessive hereditary spastic paraplegia with thin corpus callosum: a novel mutation in the SPG11 gene and further evidence for genetic heterogeneity

Background and purpose:  Autosomal Recessive Hereditary Spastic Paraplegia with Thin Corpus Callosum (AR‐HSPTCC) is a clinically and genetically heterogeneous complicated form of spastic paraplegia. Two AR‐HSPTCC loci have been assigned to chromosome 15q13‐15 (SPG11) and chromosome 8p12‐p11.21 respectively. Mutations in the SPG11 gene, encoding the spatacsin protein, have been found in the majority of SPG11 families. In this study, involvement of the SPG11 or 8p12‐p11.21 loci was investigated in five Italian families, of which four consanguineous.

Cytogenetic follow-up of chromosomal mosaicism detected in first-trimester prenatal diagnosis

To contribute to the risk assessment of true fetal mosaicism after detection of a mosaic chromosomal anomaly in chorionic villus samples (CVS) in order to enable more effective counseling and pregnancy management.

Prenatal phenotype of Williams–Beuren syndrome and of the reciprocal duplication syndrome

Copy losses/gains of the Williams–Beuren syndrome (WBS) region cause neurodevelopmental disorders with variable expressivity. The WBS prenatal diagnosis cannot be easily performed by ultrasound because only few phenotypic features can be assessed. Three WBS and the first reciprocal duplication prenatal cases are described with a review of the literature.

Complex rearrangement of the exon 6 genomic region among Opitz G/BBB Syndrome MID1 alterations

Opitz G/BBB Syndrome (OS) is a multiple congenital anomaly disorder characterized by developmental defects of midline structures. The most relevant clinical signs are ocular hypertelorism, hypospadias, cleft lip and palate, laryngo-tracheo-esophageal abnormalities, imperforate anus, and cardiac defects. Developmental delay, intellectual disability and brain abnormalities are also present. The X-linked form of this disorder is caused by mutations in the MID1 gene coding for a member of the tripartite motif family of E3 ubiquitin ligases. Here, we describe 12 novel patients that carry MID1 mutations emphasizing that laryngo-tracheo-esophageal defects are very common in OS patients and, together with hypertelorism and hypospadias, are the most frequent findings among the full spectrum of OS clinical manifestations. Besides missense and nonsense mutations, small insertions and deletions scattered along the entire length of the gene, we found that a consistent number of MID1 alterations are represented by the deletion of single coding exons. Deep characterization of one of these deletions reveals, for the first time within the MID1 gene, a complex rearrangement composed of two deletions, an inversion and a small insertion that may suggest the involvement of concurrent non-homologous mechanisms in the generation of the observed structural variant.

Attitudes of women of advanced maternal age undergoing invasive prenatal diagnosis and the impact of genetic counselling

Despite the increasing availability and effectiveness of non-invasive screening for foetal aneuploidies, most women of advanced maternal age (AMA) still opt for invasive tests. A retrospective cross-sectional survey was performed on women of AMA undergoing prenatal invasive procedures, in order to explore their motivations and the outcome of preliminary genetic counselling according to the approach (individual or group) adopted. Of 687 eligible women, 221 (32.2%) participated: 117 had received individual counselling, while 104 had attended group sessions. The two groups did not differ by socio-demographic features. The commonest reported reason to undergo invasive tests was AMA itself (67.4%), while only 10.4% of women mentioned the opportunity of making informed choices. The majority perceived as clear and helpful the information received at counselling, and only 12.7% had doubts left that, however, often concerned non-pertinent issues. The impact of counselling on risk perception and decisions was limited: a minority stated their perceived risk of foetal abnormalities had either increased (6.8%) or reduced (3.6%), and only one eventually declined invasive test. The 52.6% of women expressed a preference toward individual counselling, which also had a stronger impact on perceived risk reduction (P=0.003). Nevertheless, group counselling had a more favourable impact on both clarity of understanding and helpfulness (P=0.0497 and P=0.035, respectively). The idea that AMA represents an absolute indication for invasive tests appears deeply rooted; promotion of non-invasive techniques may require extensive educational efforts targeted to both the general population and health professionals.

Persistence of a monosomic cell line in a fetus with mosaic trisomy 8

We report on a fetus presenting with an increased nuchal translucency, in which chorionic villus sampling led to the diagnosis of mosaic trisomy 8. Ultrasound scan performed at 15+6 weeks revealed bilateral cleft lip and palate, flat facial profile, and arrhinia. Pregnancy was terminated at 16+6; postmortem examination showed additional findings including hypospadias, bilateral renal dysplasia, and focal portal fibrosis of the liver. In order to confirm the presence of trisomy 8, FISH analysis was performed in abnormal renal and hepatic tissue, which, unexpectedly, showed a higher fraction of cells with only one fluorescent probe signal (43% and 23%, respectively), if compared with normal fetal liver and kidney (3–10%). This finding is consistent with the survival in this fetus of a monosomic cell line after mitotic non‐disjunction, which is in contrast with what is generally thought about mosaic trisomy genesis. We hypothesize that the possible persistence of the monosomic cell line, in addition to the variable distribution of aneuploid cells in the body tissues, could explain the high heterogeneity of mosaic trisomy 8 phenotype.

Structural chromosomal abnormalities detected during CVS analysis and their role in the prenatal ascertainment of cryptic subtelomeric rearrangements

Mosaic structural chromosomal abnormalities observed along the trophoblast‐mesenchyme‐fetal axis, although rare, pose a difficult problem for their prognostic interpretation in prenatal diagnosis. Additional issues are raised by the presence of mosaic imbalances of the same chromosome showing different sizes in the different tissues, that is, deletions and duplications in the cytotrophoblast and mesenchyme of chorionic villi (CV). Some of these cytogenetic rearrangements originate from the post‐zygotic breakage of a dicentric chromosome or of the product of its first anaphasic breakage. Selection of the most viable cell line may result in confined placental mosaicism of the most severe imbalance, favoring the presence of the cell lines with the mildest duplications or deletions in the fetal tissues. We document three cases of ambiguous results in CV analysis due to the presence of different cell lines involving structural rearrangements of the same chromosome which were represented differently in the trophoblast and the mesenchyme. Observation by conventional karyotype of a grossly rearranged chromosome in one of the CV preparations (direct or culture) was crucial to call attention to the involved chromosomal region in other tissues (villi or amniotic fluid), allowing the prenatal diagnosis through molecular cytogenetic methods of subtelomeric rearrangements [del(7)(q36qter); del(11)(q25qter); del(20)(p13pter)]. This would have surely been undiagnosed with the routine banding technique. In conclusion, the possibility to diagnose complex abnormalities leading to cryptic subtelomeric rearrangements, together with a better knowledge of the initial/intermediate products leading to the final abnormal cryptic deletion should be added to the advantages of the CV sampling technique.