Optical coherence tomography angiography findings in Williams-Beuren syndrome.

PURPOSE: Williams-Beuren syndrome (WBS) is a rare genetic disease characterized by psychomotor delay, cardiovascular, musculoskeletal, and endocrine problems. Retinal involvement, which is not well characterized, has also been described. The purpose of this cross-sectional study is to describe the characteristics in optical coherence tomography (OCT) and OCT-angiography (OCTA) of patients with WBS. METHODS: We included patients with WBS confirmed by genetic analysis. The patients underwent OCT (30° × 25°, 61 B-scans) and OCTA (10° × 10° and 20° × 20°) examinations, all centered on the. Data on retinal thickness (total, inner and outer layers) and foveal morphology on OCT and vessel and perfusion density in OCTA (VD and PD, respectively) were collected. These data were compared with an age-matched control group. RESULTS: 22 eyes of 22 patients with WBS (10 females, mean age 31.5 years) were included. Retinal thickness (and specifically inner retinal layers) in OCT was significantly reduced in all sectors (central, parafoveal, and perifoveal) compared to the control group (p < 0.001 in all sectors). Fovea in WBS eyes was broader and shallower than controls. The PD and VD in both 10 and 20 degrees of fields in OCTA was significantly reduced in patients with WBS, in all vascular plexa (all p < 0.001). CONCLUSIONS: This study is the first to quantify and demonstrate retinal structural and microvascular alterations in patients with WBS. Further studies with longitudinal data will reveal the potential clinical relevance of these alterations.

The Contribution of Oxidative Stress to NF1-Altered Tumors.

The neurofibromatosis-1 gene (NF1) was initially characterized because its germline mutation is responsible for an inherited syndromic disease predisposing tumor development, in particular neurofibromas but also various malignancies. Recently, large-scale tumor sequencing efforts have demonstrated NF1 as one of the most frequently mutated genes in human cancer, being mutated in approximately 5-10% of all tumors, especially in malignant peripheral nerve sheath tumors and different skin tumors. NF1 acts as a tumor suppressor gene that encodes neurofibromin, a large protein that controls neoplastic transformation through several molecular mechanisms. On the other hand, neurofibromin loss due to NF1 biallelic inactivation induces tumorigenic hyperactivation of Ras and mTOR signaling pathways. Moreover, neurofibromin controls actin cytoskeleton structure and the metaphase-anaphase transition. Consequently, neurofibromin deficiency favors cell mobility and proliferation as well as chromosomal instability and aneuploidy, respectively. Growing evidence supports the role of oxidative stress in NF1-related tumorigenesis. Neurofibromin loss induces oxidative stress both directly and through Ras and mTOR signaling activation. Notably, innovative therapeutic approaches explore drug combinations that further increase reactive oxygen species to boost the oxidative unbalance of NF1-altered cancer cells. In our paper, we review NF1-related tumors and their pathogenesis, highlighting the twofold contribution of oxidative stress, both tumorigenic and therapeutic.

Ocular features in Williams-Beuren syndrome: a review of the literature.

PURPOSE OF REVIEW: The current review will discuss the pathophysiology, work-up and clinical relevance of the ocular phenotype in Williams-Beuren syndrome in detail. RECENT FINDINGS: Few case reports, case series and retrospective studies reported the ophthalmic features in Williams-Beuren syndrome, focusing on specific aspects of the ocular involvement. Recently, novel retinal findings have been described in association with the disease. SUMMARY: Numerous ocular features have been described in Williams-Beuren syndrome. Some of them, such as the stellate pattern of the iris or the retinal arteriolar tortuosity may be helpful for the diagnosis but have no significant clinical implications; others, such as strabismus and refractive errors require early treatment to reduce the risk of irreversible visual impairment. Finally, some features, such as a broad foveal pit and thinner retina still have unknown significance and require further longitudinal and multimodal studies.

New insights into the molecular basis of spinal neurofibromatosis type 1.

Spinal neurofibromatosis (SNF) is a form of neurofibromatosis type 1 (NF1) characterized by bilateral neurofibromas involving all spinal roots. The pathogenic mechanisms determining the SNF form are currently unknown. To verify the presence of genetic variants possibly related to SNF or classic NF1, we studied 106 sporadic NF1 and 75 SNF patients using an NGS panel of 286 genes encoding RAS pathway effectors and neurofibromin interactors and evaluated the expression of syndecans (SDC1, SDC2, SDC3, SDC4), the NF1 3' tertile interactors, by quantitative real-time PCR. We previously identified 75 and 106 NF1 variants in SNF and NF1 cohorts, respectively. The analysis of the distribution of pathogenic NF1 variants in the three NF1 tertiles showed a significantly higher prevalence of NF1 3' tertile mutations in SNF than in the NF1 cohort. We hypothesized a potential pathogenic significance of the 3' tertile NF1 variants in SNF. The analysis of syndecan expression on PBMCs RNAs from 16 SNF, 16 classic NF1 patients and 16 healthy controls showed that the expression levels of SDC2 and SDC3 were higher in SNF and NF1 patients than in controls; moreover, SDC2, SDC3 and SDC4 were significantly over expressed in patients mutated in the 3' tertile compared to controls. Two different mutational NF1 spectra seem to characterize SNF and classic NF1, suggesting a pathogenic role of NF1 3' tertile and its interactors, syndecans, in SNF. Our study, providing new insights on a possible role of neurofibromin C-terminal in SNF, could address effective personalized patient management and treatments.

Thyroid findings in pediatric and adult patients with PTEN hamartoma tumor syndrome: A retrospective analysis, and literature review.

PURPOSE: PTEN hamartoma tumor syndrome (PHTS) comprises a group of rare genetic conditions caused by germline mutations in PTEN gene and characterized by development of both benign and malignant lesions in many body tissues. In this study, we aimed to evaluate the incidence of thyroid findings in both adult and pediatric PHTS patients. METHODS: A retrospectively analysis conducted in 19 (13 adult and 6 pediatric) patients with PHTS, all confirmed with genetic testing, observed from 2015 to 2021 at the Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico. RESULTS: We found a thyroid involvement in 12 adult patients (92%): 11 patients had benign lesions (85%) and the remaining developed a follicular thyroid carcinoma (8.3%). The median age at time of the first available record was 30 years. Among benign lesions, multinodular goiter was the most observed finding (10/11, 91%). Only 1 out of 6 (16%) pediatric patients was diagnosed with a thyroid lesion (unifocal lesion in mild lymphocytic thyroiditis) at the age of 8 years. CONCLUSIONS: Thyroid disorders affected nearly all adult PHTS patients, but a much lower proportion of pediatric patients. We discuss about the natural history of thyroid involvement, age of PHTS clinical onset, and optimized surveillance.

Prenatal ultrasound findings associated with PIGW variants: One more piece in the FRYNS syndrome puzzle? PIGW-related prenatal findings.

OBJECTIVE: We describe the prenatal ultrasound findings and autopsy of three fetuses with multiple congenital anomalies (MCA) whose diagnostic workup suggested the same genetic etiology. We conducted a literature review to corroborate the molecular results and find evidence that the identified variants are responsible for the phenotype seen. METHODS: Trio-based Exome Sequencing (ES) analysis was performed on chorionic villus samples. We reviewed available reports dealing with prenatal manifestations of genes involved in the Glycosylphosphatidylinositols (GPI) biosynthesis defects (GPIBDs). RESULTS: Prenatal findings shared by all the three pregnancies included facial dysmorphisms, brain malformations of the posterior fossa, skeletal and genitourinary anomalies. ES analysis identified homozygous variants of uncertain significance in PIGW in the three fetuses. Prenatal findings of the three pregnancies overlapped with those previously described for PIGW variants and with those associated with PIGN, PIGV and PIGA variants. CONCLUSION: Based on the phenotypic overlap between the prenatal findings in our three cases and other cases with pathogenic variants in other genes involved in GPIBDs, we speculate that the variants identified in the three fetuses are likely causal of their phenotype and that the PIGWclinical spectrum might extend to MCA, mainly involving brain, skeletal and genitourinary systems. Moreover, we suggest that also PIGW could be involved in Fryns/Fryns-like phenotypes.

Expanding the Molecular Spectrum of ANKRD11 Gene Defects in 33 Patients with a Clinical Presentation of KBG Syndrome.

KBG syndrome (KBGS) is a neurodevelopmental disorder caused by the Ankyrin Repeat Domain 11 (ANKRD11) haploinsufficiency. Here, we report the molecular investigations performed on a cohort of 33 individuals with KBGS clinical suspicion. By using a multi-testing genomic approach, including gene sequencing, Chromosome Microarray Analysis (CMA), and RT-qPCR gene expression assay, we searched for pathogenic alterations in ANKRD11. A molecular diagnosis was obtained in 22 out of 33 patients (67%). ANKRD11 sequencing disclosed pathogenic or likely pathogenic variants in 18 out of 33 patients. CMA identified one full and one terminal ANKRD11 pathogenic deletions, and one partial duplication and one intronic microdeletion, with both possibly being pathogenic. The pathogenic effect was established by RT-qPCR, which confirmed ANKRD11 haploinsufficiency only for the three deletions. Moreover, RT-qPCR applied to six molecularly unsolved KBGS patients identified gene downregulation in a clinically typical patient with previous negative tests, and further molecular investigations revealed a cryptic deletion involving the gene promoter. In conclusion, ANKRD11 pathogenic variants could also involve the regulatory regions of the gene. Moreover, the application of a multi-test approach along with the innovative use of RT-qPCR improved the diagnostic yield in KBGS suspected patients.

Family history is key to the interpretation of exome sequencing in the prenatal context: unexpected diagnosis of Basal Cell Nevus Syndrome.

OBJECTIVES: To reach a molecular diagnosis for a family with two consecutive fetuses presenting with multiple congenital anomalies. METHODS: The two fetuses underwent prenatal ultrasound, autopsy, radiologic, and genetic investigation. Genetic analysis included karyotype and array-CGH for both fetuses and trio-based whole exome sequencing (WES) only for the second fetus. RESULTS: WES results, initially focusing on recessive or dominant de novo variants, were negative.However, as a result of new relevant information regarding family history, the variant c.648_651dup in the PTCH1 gene was identified as causative of the fetal phenotype. CONCLUSIONS: This case further highlights how WES data analysis and interpretation strongly rely on family history and robust genotype-phenotype correlation. This is even more relevant in the prenatal setting, where access to fetal phenotype is limited and prenatal recognition of many morbid genes is not fully explored. We also provide a detailed description of the prenatal manifestations of Basal Cell Nevus Syndrome.

A Translational Approach to Spinal Neurofibromatosis: Clinical and Molecular Insights from a Wide Italian Cohort.

Spinal neurofibromatosis (SNF), a phenotypic subclass of neurofibromatosis 1 (NF1), is characterized by bilateral neurofibromas involving all spinal roots. In order to deepen the understanding of SNF's clinical and genetic features, we identified 81 patients with SNF, 55 from unrelated families, and 26 belonging to 19 families with at least 1 member affected by SNF, and 106 NF1 patients aged >30 years without spinal tumors. A comprehensive NF1 mutation screening was performed using NGS panels, including NF1 and several RAS pathway genes. The main features of the SNF subjects were a higher number of internal neurofibromas (p < 0.001), nerve root swelling (p < 0.001), and subcutaneous neurofibromas (p = 0.03), while hyperpigmentation signs were significantly less frequent compared with the classical NF1-affected cohorts (p = 0.012). Fifteen patients underwent neurosurgical intervention. The histological findings revealed neurofibromas in 13 patients and ganglioneuromas in 2 patients. Phenotypic variability within SNF families was observed. The proportion of missense mutations was higher in the SNF cases than in the classical NF1 group (21.40% vs. 7.5%, p = 0.007), conferring an odds ratio (OR) of 3.34 (CI = 1.33−10.78). Two unrelated familial SNF cases harbored in trans double NF1 mutations that seemed to have a subclinical worsening effect on the clinical phenotype. Our study, with the largest series of SNF patients reported to date, better defines the clinical and genetic features of SNF, which could improve the management and genetic counseling of NF1.

Monogenic Syndromes with Congenital Heart Diseases in Newborns (Diagnostic Clues for Neonatologists): A Critical Analysis with Systematic Literature Review.

Congenital heart disease (CHD), the most common major congenital anomaly, is associated with a genetic syndrome (chromosomal anomalies, genomic disorders, or monogenic disease) in 30% of patients. The aim of this systematic review was to evaluate if, in the neonatal setting, clinical clues that orient the diagnostic path can be identified. For this purpose, we revised the most frequent dysmorphic features described in newborns with CHD, comparing those associated with monogenic syndromes (MSG) with the ones reported in newborns with genomic disorders. For this systematic review according to PRISMA statement, we used PubMed, Medline, Google Scholar, Scopus database, and search terms related to CHD and syndrome. We found a wide range of dysmorphisms (ocular region, ears, mouth, and/or palate and phalangeal anomalies) detected in more than half of MSGs were found to be associated with CHDs, but those anomalies are also described in genomic rearrangements syndromes with equal prevalence. These findings confirmed that etiological diagnosis in newborns is challenging, and only the prompt and expert recognition of features suggestive of genetic conditions can improve the selection of appropriate, cost-effective diagnostic tests. However, in general practice, it is crucial to recognize clues that can suggest the presence of a genetic syndrome, and neonatologists often have the unique opportunity to be the first to identify abnormalities in the neonate.

Simultaneous Detection of NF1, SPRED1, LZTR1, and NF2 Gene Mutations by Targeted NGS in an Italian Cohort of Suspected NF1 Patients.

Neurofibromatosis type 1 (NF1) displays overlapping phenotypes with other neurocutaneous diseases such as Legius Syndrome. Here, we present results obtained using a next generation sequencing (NGS) panel including NF1, NF2, SPRED1, SMARCB1, and LZTR1 genes on Ion Torrent. Together with NGS, the Multiplex Ligation-Dependent Probe Amplification Analysis (MLPA) method was performed to rule out large deletions/duplications in NF1 gene; we validated the MLPA/NGS approach using Sanger sequencing on DNA or RNA of both positive and negative samples. In our cohort, a pathogenic variant was found in 175 patients; the pathogenic variant was observed in NF1 gene in 168 cases. A SPRED1 pathogenic variant was also found in one child and in a one year old boy, both NF2 and LZTR1 pathogenic variants were observed; in addition, we identified five LZTR1 pathogenic variants in three children and two adults. Six NF1 pathogenic variants, that the NGS analysis failed to identify, were detected on RNA by Sanger. NGS allows the identification of novel mutations in five genes in the same sequencing run, permitting unambiguous recognition of disorders with overlapping phenotypes with NF1 and facilitating genetic counseling and a personalized follow-up.

Non-Coding RNA and Tumor Development in Neurofibromatosis Type 1: ANRIL Rs2151280 Is Associated with Optic Glioma Development and a Mild Phenotype in Neurofibromatosis Type 1 Patients.

Non-coding RNAs (ncRNAs) are known to regulate gene expression at the transcriptional and post-transcriptional levels, chromatin remodeling, and signal transduction. The identification of different species of ncRNAs, microRNAs (miRNAs), circular RNAs (circRNAs), and long ncRNAs (lncRNAs)-and in some cases, their combined regulatory function on specific target genes-may help to elucidate their role in biological processes. NcRNAs' deregulation has an impact on the impairment of physiological programs, driving cells in cancer development. We here carried out a review of literature concerning the implication of ncRNAs on tumor development in neurofibromatosis type 1 (NF1), an inherited tumor predisposition syndrome. A number of miRNAs and a lncRNA has been implicated in NF1-associated tumors, such as malignant peripheral nerve sheath tumors (MPNSTs) and astrocytoma, as well as in the pathognomonic neurofibromas. Some authors reported that the lncRNA ANRIL was deregulated in the blood of NF1 patients with plexiform neurofibromas (PNFs), even if its role should be further elucidated. We here provided original data concerning the association of a specific genotype about ANRIL rs2151280 with the presence of optic gliomas and a mild expression of the NF1 phenotype. We also detected the LOH of ANRIL in different tumors from NF1 patients, supporting the involvement of ANRIL in some NF1-associated tumors. Our results suggest that ANRIL rs2151280 may be a potential diagnostic and prognostic marker, addressing early diagnosis of optic glioma and predicting the phenotype severity in NF1 patients.

Risk of Optic Pathway Glioma in Neurofibromatosis Type 1: No Evidence of Genotype-Phenotype Correlations in A Large Independent Cohort.

The occurrence of optic pathway gliomas (OPGs) in children with neurofibromatosis type 1 (NF1) still raises many questions regarding screening and surveillance because of the lack of robust prognostic factors. Recent studies of an overall cohort of 381 patients have suggested that the genotype may be the main determinant of the development of OPG, with the risk being higher in patients harbouring NF1 mutations in the 5' tertile and the cysteine/serine-rich domain. In an attempt to confirm this hypothesis, we used strict criteria to select a large independent cohort of 309 NF1 patients with defined constitutional NF1 mutations and appropriate brain images (255 directly enrolled and 54 as a result of a literature search). One hundred and thirty-two patients had OPG and 177 did not. The association of the position (tertiles and functional domains) and type of NF1 mutation with the development of OPG was analysed using the χ2 test and Fisher's exact probability test; odds ratios (ORs) with 95% confidence intervals were calculated, and Bonferroni's correction for multiple comparisons was applied; multiple logistic regression was also used to study genotype-phenotype associations further. Our findings show no significant correlation between the site/type of NF1 mutation and the risk of OPG, and thus do not support the hypothesis that certain constitutional mutations provide prognostic information in this regard. In addition, we combined our cohort with a previously described cohort of 381 patients for a total of 690 patients and statistically re-analysed the results. The re-analysis confirmed that there were no correlations between the site (tertile and domain) and the risk of OPG, thus further strengthening our conclusions.

Small supernumerary marker chromosomes: A legacy of trisomy rescue?

We studied by a whole genomic approach and trios genotyping, 12 de novo, nonrecurrent small supernumerary marker chromosomes (sSMC), detected as mosaics during pre- or postnatal diagnosis and associated with increased maternal age. Four sSMCs contained pericentromeric portions only, whereas eight had additional non-contiguous portions of the same chromosome, assembled together in a disordered fashion by repair-based mechanisms in a chromothriptic event. Maternal hetero/isodisomy was detected with a paternal origin of the sSMC in some cases, whereas in others two maternal alleles in the sSMC region and biparental haplotypes of the homologs were detected. In other cases, the homologs were biparental while the sSMC had the same haplotype of the maternally inherited chromosome. These findings strongly suggest that most sSMCs are the result of a multiple-step mechanism, initiated by maternal meiotic nondisjunction followed by postzygotic anaphase lagging of the supernumerary chromosome and its subsequent chromothripsis.

Trabecular Bone Score (TBS) and Bone Metabolism in Patients Affected with Type 1 Neurofibromatosis (NF1).

In patients with neurofibromatosis type 1 (NF1), decreased bone mineral density (BMD) and low levels of 25-hydroxy vitamin D3 (25OHD) have been reported. Recently, the trabecular bone score (TBS) measurement has been proposed as index of bone microarchitecture and fracture risk. In 74 NF1 patients (48 females, 26 males, age 41 ± 12), we measured TBS and investigated clinical stage, lifestyle, vitamin D, serum bone turnover markers, vertebral and femoral BMD. A homogenous cohort of 61 healthy subjects was used as control group. TBS was lower in NF1 patients (1.266 ± 0.113 vs. 1.346 ± 0.105) without differences between sexes. No correlations with 25OHD, low exercise, low calcium intake, reduced sun exposure, and number of skin neurofibromas were observed. As expected, hypovitaminosis D was common (98.6%), as well as BMD reduction in hip and spine sites: In NF1 patients, bone texture evaluated by TBS was low in both sexes without any correlation with clinical or metabolic parameters, suggesting a direct role of the fibromin mutation.

Correction: The absence that makes the difference: choroidal abnormalities in Legius syndrome.

Correction to: Journal of Human Genetics advance online publication 27 July 2017; https://doi.org/10.1038/jhg.2017.78.

Early neonatal Glutaric aciduria type I hidden by perinatal asphyxia: a case report.

BACKGROUND: Perinatal asphyxia (PA) occurs in about 2 to 10 per 1000 live full-term births. Although neonatal epileptic seizures are observed in up to 60% of cases, PA may mimic or subtend other conditions. Hypoxia related brain injury is particularly relevant, as it may have permanent effects on neuropsychomotor development. Antepartum obstetric conditions, may, in turn, lead to hypoxic-ischemic damage to the fetus and the newborn, often underlying PA. Herein, a case of PA that hid and triggered signs and symptoms of Glutaric Aciduria type I (GA-I), is reported. CASE PRESENTATION: R.F. was born at term after prolonged labour, by induced vaginal delivery with the Kristeller manoeuvre. He presented with severe asphyxia and asystoly. Immediate cardiopulmonary resuscitation promptly restored cardiorespiratory parameters, allowing for early extubation 30 min after. During the following hours, severe axial muscle hypotonia with an increased tone of the limb extensor muscles became evident. The absence of crying and archaic reflexes persisted and there was an onset of generalized tonic or clonic seizure. First level metabolic and inflammatory markers were within the normal range. An inherited metabolic disease was then suspected, due to the persistent clinical signs of severe neurological damage without any detectable septic parameter. GA-I was assessed and specific treatment started without any clinical improvement, although ensuring adequate growth and metabolic control. Thereafter, the baby developed a severe encephalopathy with drug resistant epileptic seizures. The progression of the neurological damage and a CVC-related sepsis led him to exitus at 2 years. CONCLUSIONS: To the best of our knowledge, this is the first case of early post-natal onset of GA-I reported in literature to date, in the absence of expanded newborn screening (NBS) programme. As expanded NBS programmes for inborn errors of metabolism have not yet been internationally adopted, we are of the opinion that such diseases may well be hidden by misleading signs and symptoms imputable to other more frequent harmful clinical conditions. Moreover, it would be advisable that neonatologists be trained to include GA-I in the differential diagnosis of neurological damage secondary to PA.

The absence that makes the difference: choroidal abnormalities in Legius syndrome.

Neurofibromatosis type 1 (NF1) is an hereditary disorder characterized by abnormal proliferation of multiple tissues of neural crest origin, and presents mainly with multiple café-au-lait macules, axillary freckling and neurofibromas. Choroidal involvement in NF1 patients has been studied, thanks to the development of non-invasive tools such as infrared monochromatic light during fundus examination, which showed bright patchy lesions consistent with choroidal nodules. Choroidal abnormalities identified with near-infrared reflectance have reported with a frequency of up to 100% in NF1, and have been recently been proposed as a novel diagnostic criterion for NF1. Legius syndrome can be clinically indistinguishable from NF1 and results in a small percentage of individuals being misdiagnosed. We investigated the presence of choroidal abnormalities in Legius syndrome to determine their specificity to NF1 and their potential usefulness as a novel diagnostic criterion for NF1. We examined the fundus of 16 eyes by confocal scanning laser ophthalmoscopy with infrared monochromatic light in eight patients with molecularly confirmed Legius syndrome. No abnormalities were observed, confirming the diagnostic value of choroidal abnormalities for the diagnosis of NF1.

COLD-PCR and microarray: two independent highly sensitive approaches allowing the identification of fetal paternally inherited mutations in maternal plasma.

BACKGROUND: Until now, non-invasive prenatal diagnosis of genetic diseases found only limited routine applications. In autosomal recessive diseases, it can be used to determine the carrier status of the fetus through the detection of a paternally inherited disease allele in cases where maternal and paternal mutated alleles differ. METHODS: Conditions for non-invasive identification of fetal paternally inherited mutations in maternal plasma were developed by two independent approaches: coamplification at lower denaturation temperature-PCR (COLD-PCR) and highly sensitive microarrays. Assays were designed for identifying 14 mutations, 7 causing ß-thalassaemia and 7 cystic fibrosis. RESULTS: In total, 87 non-invasive prenatal diagnoses were performed by COLD-PCR in 75 couples at risk for ß-thalassaemia and 12 for cystic fibrosis. First, to identify the more appropriate methodology for the analysis of minority mutated fetal alleles in maternal plasma, both fast and full COLD-PCR protocols were developed for the most common Italian ß-thalassaemia Cd39 and IVSI.110 mutations. In 5 out of 31 samples, no enrichment was obtained with the fast protocol, while full COLD-PCR provided the correct fetal genotypes. Thus, full COLD-PCR protocols were developed for all the remaining mutations and all analyses confirmed the fetal genotypes obtained by invasive prenatal diagnosis. Microarray analysis was performed on 40 samples from 28 couples at risk for ß-thalassaemia and 12 for cystic fibrosis. Results were in complete concordance with those obtained by both COLD-PCR and invasive procedures. CONCLUSIONS: COLD-PCR and microarray approaches are not expensive, simple to handle, fast and can be easily set up in specialised clinical laboratories where prenatal diagnosis is routinely performed.