Corpus callosum abnormalities, intellectual disability, speech impairment, and autism in patients with haploinsufficiency of ARID1B.

Corpus callosum abnormalities, intellectual disability, speech impairment, and autism in patients with haploinsufficiency of ARID1B. Corpus callosum abnormalities are common brain malformations with a wide clinical spectrum ranging from severe intellectual disability to normal cognitive function. The etiology is expected to be genetic in as much as 30-50% of the cases, but the underlying genetic cause remains unknown in the majority of cases. By next-generation mate-pair sequencing we mapped the chromosomal breakpoints of a patient with a de novo balanced translocation, t(1;6)(p31;q25), agenesis of corpus callosum (CC), intellectual disability, severe speech impairment, and autism. The chromosome 6 breakpoint truncated ARID1B which was also truncated in a recently published translocation patient with a similar phenotype. Quantitative polymerase chain reaction (Q-PCR) data showed that a primer set proximal to the translocation showed increased expression of ARID1B, whereas primer sets spanning or distal to the translocation showed decreased expression in the patient relative to a non-related control set. Phenotype-genotype comparison of the translocation patient to seven unpublished patients with various sized deletions encompassing ARID1B confirms that haploinsufficiency of ARID1B is associated with CC abnormalities, intellectual disability, severe speech impairment, and autism. Our findings emphasize that ARID1B is important in human brain development and function in general, and in the development of CC and in speech development in particular.

X-chromosome duplications in males with mental retardation: pathogenic or benign variants?

Studies to identify copy number variants (CNVs) on the X-chromosome have revealed novel genes important in the causation of X-linked mental retardation (XLMR). Still, for many CNVs it is unclear whether they are associated with disease or are benign variants. We describe six different CNVs on the X-chromosome in five male patients with mental retardation that were identified by conventional karyotyping and single nucleotide polymorphism array analysis. One deletion and five duplications ranging in size from 325 kb to 12.5 Mb were observed. Five CNVs were maternally inherited and one occurred de novo. We discuss the involvement of potential candidate genes and focus on the complexity of X-chromosomal duplications in males inherited from healthy mothers with different X-inactivation patterns. Based on size and/or the presence of XLMR genes we were able to classify CNVs as pathogenic in two patients. However, it remains difficult to decide if the CNVs in the other three patients are pathogenic or benign.

Further delineation of Pitt-Hopkins syndrome: phenotypic and genotypic description of 16 novel patients.

BACKGROUND: Haploinsufficiency of the gene encoding for transcription factor 4 (TCF4) was recently identified as the underlying cause of Pitt-Hopkins syndrome (PTHS), an underdiagnosed mental-retardation syndrome characterised by a distinct facial gestalt, breathing anomalies and severe mental retardation. METHODS: TCF4 mutational analysis was performed in 117 patients with PTHS-like features. RESULTS: In total, 16 novel mutations were identified. All of these proven patients were severely mentally retarded and showed a distinct facial gestalt. In addition, 56% had breathing anomalies, 56% had microcephaly, 38% had seizures and 44% had MRI anomalies. CONCLUSION: This study provides further evidence of the mutational and clinical spectrum of PTHS and confirms its important role in the differential diagnosis of severe mental retardation.

Molecular and clinical characterization of de novo and familial cases with microduplication 3q29: guidelines for copy number variation case reporting.

Microdeletions of 3q29 have previously been reported, but the postulated reciprocal microduplication has only recently been observed. Here, cases from four families, two ascertained in Toronto (Canada) and one each from Edinburgh (UK) and Leiden (Netherlands), carrying microduplications of 3q29 are presented. These families have been characterized by cytogenetic and molecular techniques, and all individuals have been further characterized with genome-wide, high density single nucleotide polymorphism (SNP) arrays run at a single centre (The Centre for Applied Genomics, Toronto). In addition to polymorphic copy-number variants (CNV), all carry duplications of 3q29 ranging in size from 1.9 to 2.4 Mb, encompassing multiple genes and defining a minimum region of overlap of about 1.6 Mb bounded by clusters of segmental duplications that is remarkably similar in location to previously reported 3q29 microdeletions. Consistent with other reports, the phenotype is variable, although developmental delay and significant ophthalmological findings were recurrent, suggesting that dosage sensitivity of genes located within 3q29 is important for eye and CNS development. We also consider CNVs found elsewhere in the genome for their contribution to the phenotype. We conclude by providing preliminary guidelines for management and anticipatory care of families with this microduplication, thereby establishing a standard for CNV reporting.

Congenital disorder of glycosylation type Ia presenting with hydrops fetalis.

There is a growing awareness that inborn errors of metabolism can be a cause of non-immune hydrops fetalis. The association between congenital disorders of glycosylation (CDG) and hydrops fetalis has been based on one case report concerning two sibs with hydrops fetalis and CDG-Ik. Since then two patients with hydrops-like features and CDG-Ia have been reported. Two more unrelated patients with CDG-Ia who presented with hydrops fetalis are reported here, providing definite evidence that non-immune hydrops fetalis can be caused by CDG-Ia. The presence of congenital thrombocytopenia and high ferritin levels in both patients was remarkable. These might be common features in this severe form of CDG. Both patients had one severe mutation in the phosphomannomutase 2 gene, probably fully inactivating the enzyme, and one milder mutation with residual activity, as had the patients reported in literature. The presence of one severe mutation might be required for the development of hydrops fetalis. CDG-Ia should be considered in the differential diagnosis of hydrops fetalis and analysis of PMM activity in chorionic villi or amniocytes should also be considered.

Prenatal diagnosis and confirmation of the acrofacial dysostosis syndrome type Rodriguez.

The group of acrofacial dysostosis (AFD) syndromes is very heterogeneous and contains many different entities. In 1990, Rodriguez et al. [1990: Am J Med Genet 35:484-489] described a new type of AFD characterized by severe mandibular hypoplasia, phocomelia and oligodactyly of the upper limbs, absence of fibulae, microtia, cleft palate, internal organ anomalies including arrhinencephaly and abnormal lung lobulation, and early lethality. We describe another case of AFD type Rodriguez, identified by prenatal ultrasonography at 25 weeks of gestation.

Early fetal anomaly scanning in a population at increased risk of abnormalities.

OBJECTIVES: To determine the effectiveness of early fetal anomaly scanning in a population at risk of fetal anomalies. DESIGN: A prospective study in a tertiary center of 101 consecutive fetuses at risk of congenital anomalies at 11-14 weeks of gestation. RESULTS: The principal (93/101 = 92%) reason for referral was having a previously affected infant. Nine (9/101 = 9%) fetuses were shown to have structural anomalies at the 11-14-week scan. In five of nine structurally affected fetuses, the nature of the anomalies was similar to that established in a previously affected pregnancy, four of which had a recurrence of an autosomal recessive syndrome. In two fetuses with a normal 11-14-week scan, anomalies were detected at the 18-21-week (arthrogryposis) or 30-week (cardiomyopathy) scans. CONCLUSIONS: The majority of fetal anomalies can be diagnosed in the late first/early second trimesters of pregnancy. This will be of particular advantage to those women who are at high risk of having affected offspring. However, as fetal anomalies may present at varying gestational ages, the standard 18-21-week scan cannot be abandoned. The effectiveness of the early pregnancy scan depends on the natural history of anomalies (gestational age at onset) and the variable phenotypic expression of anomalies/syndromes.

Unilateral multicystic dysplastic kidney: a combined pre- and postnatal assessment.

OBJECTIVE: To review the prenatal assessment of associated renal pathology, non-renal pathology and renal biometry, fetal outcome and postnatal urological management in the presence of unilateral fetal multicystic dysplastic kidney. METHODS: A total of 38 singleton pregnancies with fetal unilateral multicystic dysplastic kidney was studied over a 13-year period. Prenatally, fetal biometry, including head and abdominal circumferences and largest longitudinal diameter of the affected and contralateral kidneys, was performed. The amount of amniotic fluid was assessed. Fetal karyotyping was offered in cases of contralateral renal or non-renal pathology. A MAG 3 scan and voiding cystogram was performed approximately 4 weeks after delivery to establish renal function and to exclude urinary reflux. RESULTS: Unilateral fetal multicystic dysplastic kidney was left-sided in 53% and right-sided in 47% of cases. The fetus was male in 63% and female in 37% of cases. Associated renal and non-renal pathology existed in 21% and 5% of cases, respectively. The fetal karyotype in these subsets was always normal. The longitudinal diameter of the multicystic dysplastic kidney was above the 95th centile in 87%. There was polyhydramnios in three cases and oligohydramnios in two cases. The prematurity rate was 16%. Postnatal examination revealed a non-functional multicystic kidney in 87% (33/38) of cases. Following surgical removal of the affected kidney, these infants progressed normally. Of the remaining five infants, four died because of associated anomalies and one infant developed normally without surgery. CONCLUSIONS: Fetal outcome is determined by associated renal and/or non-renal structural pathology and not by the size/location of the unilateral multicystic dysplastic kidney or amniotic fluid volume.

Lymphangiectasia with persistent Müllerian derivatives: confirmation of autosomal recessive Urioste syndrome.

We report on a sibship with protein-losing enteropathy related to intestinal lymphangiectasia, a peculiar face, and genital anomalies. The parents are distantly related and from Dutch ancestry. The first patient was born with a protein-losing enteropathy, craniofacial anomalies, and renal defects. At 1 year of age, she died of severe complications of the protein-losing enteropathy and respiratory distress. Her brother was a cytogenetically normal male fetus identified by prenatal ultrasound at 19 weeks with similar anomalies. The pregnancy was terminated at 20 weeks. Autopsy showed müllerian duct remnants. These cases seem to confirm the Urioste syndrome [Urioste et al., 1993: Am J Med Genet 47:494-503]. Although it was previously only reported in 46,XY individuals, this report of a consanguineous family with an affected sibship of both sexes suggests it to be an autosomal recessive entity.

Prenatal diagnosis of type A1 brachydactyly.

Brachydactyly can occur as an isolated malformation or as part of numerous syndromes. Prenatal assessment of brachydactyly may be especially helpful in multiple anomaly syndromes associated with hand and/or finger anomalies. In isolated type A1 brachydactyly, which is an autosomal dominant disorder, all middle phalanges of the fingers and toes are affected. We present a fetus with type A1 brachydactyly inherited from the mother and grandmother.

Early prenatal sonographic diagnosis and follow-up of Jeune syndrome.

Jeune syndrome or asphyxiating thoracic dysplasia is an autosomal recessive osteochondrodysplasia. It is one of the six short-rib (polydactyly) syndromes. The disease has a wide spectrum of manifestations, ranging from a latent to a mild or lethal condition. We describe the prenatal sonographic diagnosis of Jeune syndrome at 14 weeks of gestation in a fetus at risk for this condition, and the development of the syndrome throughout the pregnancy.

The diagnostic performance of cytogenetic investigation in amniotic fluid cells and chorionic villi.

First-trimester chorionic villus sampling has not reached the popularity of second-trimester amniocentesis in prenatal cytogenetic diagnosis, in contrast to initial expectations. We investigated whether a difference in the diagnostic performances of cytogenetic investigation in amniotic fluid (AF) cells and chorionic villi in favour of AF-cells might justify this. Diagnostic performance was measured as laboratory failure rate, karyotype quality (G-band score, rate of follow-up samples, rate of wrong diagnoses), and karyotype representativity (rate of follow-up samples, rate of wrong diagnoses). From 1993-1999, 11 883 AF-samples were investigated (AF-cells). In chorionic villi, short term culture preparations solely were karyotyped from 1993-1996 (n=3499) (STC-villi), short and long-term culture preparations simultaneously provided a sufficient amount of tissue being available from 1997 onwards (n=1829) ((STC+LTC)-villi). Laboratory failure rates were the same after amniocentesis (0.40%) and chorionic villus sampling (0.50%). G-band scores (mean+/-SD) were equal in AF-cells (373+/-38.1) and LTC-villi (364+/-32.6) but significantly lower in STC-villi (311+/-34.6) (p=0.001). Follow-up sampling rates because of quality reasons were the same in AF-cells (0.14%), STC- villi (0.13%) and (STC+LTC)-villi (0.11%). Two wrong diagnoses turned up among AF-cells. Follow-up sampling rates because of representativity reasons differed significantly between AF-cells (0.10%), (STC+LTC)-villi (1.31%), and STC-villi (1.99%) (p<0.001). However, the ratios of the total numbers of follow-up samples and uncertain or abnormal cytogenetic results in STC, and (STC+LTC)-villi at cytogenetic risks > or =3% (0.132 and 0.160, respectively) were equal to that in AF-cells at risks <3% (0.155). Two wrong diagnoses were made in STC-villi. Diagnostic performance improved in the rank order of STC-villi, (STC+LTC)-villi and AF-cells. At cytogenetic risks > or =3%, (STC+LTC)-villi showed a diagnostic performance equal to that in AF-cells. This might justify a selective use of chorionic villus sampling.

Accuracy of abnormal karyotypes after the analysis of both short- and long-term culture of chorionic villi.

We report in detail the cytogenetic results of 1838 consecutive chorionic villus samples with the availability of both short-term culture (STC-villi) and long-term culture (LTC-villi) preparations in 1561 cases (84.9%). A high degree of laboratory success (99.5%) and diagnostic accuracy (99.8%) was observed; in four cases of low mosaicism, all four associated with the final birth of a normal child, a small risk of uncertainty was accepted. The combined analysis of STC- and LTC-villi reduced follow-up amniocenteses by one-third in comparison with the analysis of STC-villi alone. We believe that the desired level of quality and accuracy of prenatal cytogenetics in chorionic villi can only be achieved when both STC- and LTC-villi are available. We conclude that CVS might then be the mode of prenatal diagnosis of first choice in pregnancies with a high (cytogenetic) risk.

In-utero diagnosis of mucopolysaccharidosis type VII in a fetus with an enlarged nuchal translucency.

Mucopolysaccharidosis type VII was diagnosed prenatally during the first pregnancy of a Turkish consanguineous couple, following diagnostic work-up of an increased nuchal translucency detected by ultrasound at 13 weeks of gestation. Mucopolysaccharidosis type VII (MPS VII) or Sly syndrome is a rare autosomal recessive lysosomal storage disease, caused by the deficiency of the enzyme beta-glucuronidase. The most severe form of MPS VII manifests itself by non-immune fetal hydrops. Tests for the diagnosis of metabolic disorders, especially lysosomal diseases, are essential when the major causes of hydrops fetalis have been excluded. The presence of a beta-glucosidase deficiency, Gaucher's disease, in the infant of the patient's sister emphasizes the importance of a complete family history in consanguineous couples and the risk for several recessive diseases in some families.

Congenital microcephaly detected by prenatal ultrasound: genetic aspects and clinical significance.

OBJECTIVE: The aim of this study was to analyze fetuses with prenatally diagnosed microcephaly including the nature of associated anomalies and the genetic-diagnostic implications. DESIGN: Retrospective study design. METHODS: A total of 30 fetuses with reliable dates and with prenatally diagnosed microcephaly as a common feature were analyzed. RESULTS: Microcephaly was diagnosed at a mean gestational age of 28 weeks. More than half of the fetuses were also small for gestational age. Five subsets of microcephaly emerged from this study: (1) isolated microcephaly (16.7%); (2) microcephaly due to holoprosencephaly (16.7%); (3) microcephaly associated with chromosomal disorders (23.3%); (4) microcephaly as part of a genetic syndrome (20.0%); and (5) microcephaly as part of multiple anomalies (23.3%). CONCLUSIONS: In 25 out of 30 infants microcephaly proved to be part of a complex problem, emphasizing the need of a meticulous search for structural anomalies and fetal karyotyping when biometric data are not according to gestational age. The etiologic heterogeneity and variability of microcephaly in genetic syndromes are among the more difficult issues in prenatal ultrasound in pregnancies either with an incidental finding of this anomaly, or in cases with a recurrence risk. The complex situations described in this study demonstrate the importance of follow up, post-mortem investigation and careful genetic counseling.

A frame-shift mutation in the type I parathyroid hormone (PTH)/PTH-related peptide receptor causing Blomstrand lethal osteochondrodysplasia.

Blomstrand osteochondrodysplasia (BOCD) is a rare lethal skeletal dysplasia characterized by accelerated endochondral and intramembranous ossification. Comparison of the characteristics of BOCD with type I PTH/PTH-related peptide (PTHrP) receptor-ablated mice reveals striking similarities that are most prominent in the growth plate. In both cases, the growth plate is reduced in size due to a strongly diminished zone of resting cartilage and the near absence of columnar arrangement of proliferating chondrocytes. This overall similarity suggested that an inactivating mutation of the PTH/PTHrP receptor might be the underlying genetic defect causing BOCD. Indeed, inactivating mutations of the PTH/PTHrP receptor have been recently identified in two cases of BOCD. We describe here a novel inactivating mutation in the PTH/PTHrP receptor. Sequence analysis of all coding exons of the type I PTH/ PTHrP receptor gene and complementary DNA of a case with BOCD identified a homozygous point mutation in exon EL2 in which one nucleotide (G at position 1122) was absent. The mutation was inherited from both parents, supporting the autosomal recessive nature of the disease. The missense mutation resulted in a shift in the open reading frame, leading to a truncated protein that completely diverged from the wild-type sequence after amino acid 364. The mutant receptor, therefore, lacked transmembrane domains 5, 6, and 7; the connecting intra- and extracellular loops; and the cytoplasmic tail. Functional analysis of the mutant receptor in COS-7 cells and of dermal fibroblasts obtained from the case proved that the mutation was indeed inactivating. Neither the transiently transfected COS-7 cells nor the dermal fibroblasts responded to a challenge with PTH or PTHrP with a rise in intracellular cAMP levels, in sharp contrast to control cells. Our results provide further evidence that BOCD is caused by inactivating mutations of the type I PTH/PTHrP receptor and underscore the importance of this receptor in mammalian skeletal development.

Amniocentesis or chorionic villus sampling in multiple gestations? Experience with 500 cases.

500 women with multiple pregnancies underwent amniocentesis or chorionic villus (CV) sampling at our department between January 1988 and July 1997. The aim of this retrospective study was to evaluate the laboratory aspects and the consequences of discordant results in these pregnancies in relation to the method of sampling. Uncertain results in one or both samples, requiring further investigation were more frequent in CV samples (eight times in 163 paired samples, 5 per cent) than in amniotic fluid (AF) samples (once in 298 paired samples, 0.3 per cent). Sampling one fetus twice (erroneous sampling) was seen only once among 163 pregnancies with two CV samples in our study. Cross contamination due to mixed sampling was discovered in two of seven pregnancies that underwent DNA diagnosis in CV and might be a rather regular occuring phenomenon. In none of the 500 pregnancies mixed sampling caused diagnostic dilemmas. A third sampling problem, maternal cell contamination caused a diagnostic problem once among the AF samples. Selective fetal reduction appeared safer after CV sampling than after amniocentesis. Subsequently, CV sampling instead of amniocentesis has become the method of choice for prenatal diagnosis in multiple pregnancies in our department.

Prenatally diagnosed fetal ventriculomegaly; prognosis and outcome.

The purpose of the present study was to determine the postnatal outcome and prognostic factors of prenatally diagnosed ventriculomegaly, and to establish the relationship between prenatal sonographic measurements and postnatal psychomotor development. A total of 42 singleton pregnancies with sonographically determined fetal ventriculomegaly at 20-38 weeks' gestation were reviewed, together with follow-up data on postnatal outcome at a mean of 29 months after delivery. Sonographic measurements included head circumference, cerebral lateral ventricular diameter at the anterior and posterior horn level, and hemisphere diameter. Classification of psycho-motor development consisted of assessment of motoric behaviour, speech, communication and social skills ('Van Wiechen' classification). Perinatal mortality rate was 38 per cent, of which half were directly associated with cephalocentesis. Only the ventricle/hemisphere ratio for the anterior and posterior horn of the lateral cerebral ventricles was significantly higher among perinatal deaths than amongst the survivors. Within the subset of survivors (n = 26), psycho-motor development was normal in 46 per cent. Postnatal examination revealed syndrome anomalies in five infants, of which four were associated with psycho-motor retardation. Prenatally diagnosed ventriculomegaly has a poor postnatal outcome with more than 50 per cent of the live-born infants demonstrating abnormal psycho-motor development. The predictive value of fetal biometric measurements is poor. The presence of syndromal anomalies emphasizes the need for genetic counselling in future pregnancies.

Early transvaginal ultrasonographic diagnosis of Beemer-Langer dysplasia: a report of two cases.

The early second-trimester sonographic diagnosis of two infants with short rib (polydactyly) dysplasia type IV (Beemer-Langer dysplasia) is presented. In addition to short ribs, this syndrome is characterized by short limbs with or without polydactyly. There are often associated defects, particularly neural-tube anomalies. The occurrence of consanguinity and of four affected siblings in this family support autosomal recessive inheritance.