13q Deletion and central nervous system anomalies: further insights from karyotype-phenotype analyses of 14 patients

From Genes to Ambiguity: A Case Study Exploring the Enigmatic Connection Between Chromosome 13q Deletion Syndrome and Ambiguous Genitalia

During development, the deletion of DNA from chromosome 13's short arm (q) causes a chromosomal abnormality known as chromosome 13q deletion syndrome. Chromosome 13 terminal deletions are rare and may cause various congenital disabilities, and only a few cases have been reported in the literature. The extent of chromosome 13q deletion syndrome changes lacks consistent clinical features, with no recorded cases of genital ambiguity until now. We report the case of a newborn male patient whose testes had descended on both sides; he had ambiguous genitalia, and the dorsal surface of his penis was attached to his scrotal sac. An abnormal karyotype (46, XY, deletion (13) q33) was discovered by using a G-banding analysis of chromosomes in a blood sample taken from the periphery, which revealed a deletion of chromosome 13 at the end of the first 10 cells. We can better characterize chromosome 13q deletions by establishing stronger correlations between karyotype and the distinctive phenotypes of haploinsufficient genes found on the chromosome.

Fold-back mechanism originating inv-dup-del rearrangements in chromosomes 13 and 15

Intrachromosomal rearrangements involve a single chromosome and can be formed by several proposed mechanisms. We reported two patients with intrachromosomal duplications and deletions, whose rearrangements and breakpoints were characterized through karyotyping, chromosomal microarray, fluorescence in situ hybridization, whole-genome sequencing, and Sanger sequencing. Inverted duplications associated with terminal deletions, known as inv-dup-del rearrangements, were found in 13q and 15q in these patients. The presence of microhomology at the junction points led to the proposal of the Fold-back mechanism for their formation. The use of different high-resolution techniques allowed for a better characterization of the rearrangements, with Sanger sequencing of the junction points being essential to infer the mechanisms of formation as it revealed microhomologies that were missed by the previous techniques. A karyotype-phenotype correlation was also performed for the characterized rearrangements.

Prenatal diagnosis of distal 13q deletion syndrome in a fetus with esophageal atresia: a case report and review of the literature

BACKGROUND

Chromosome 13q deletion syndrome shows variable clinical features related to the different potential breakpoints in chromosome 13q. The severely malformed phenotype is known to be associated with the deletion of a critical region in 13q32. However, esophageal atresia is a rare symptom and the relevant region is unknown. Thus, determining the association between accurate breakpoints and new clinical features is essential.

CASE PRESENTATION

A 28-year-old Japanese primigravid woman was referred for fetal growth restriction, absence of a gastric bubble, cerebellar hypoplasia, overlapping fingers, and polyhydramnios at 31 weeks gestation. At 38 + 0 weeks, she delivered a 1774 g female infant. The infant presented with isolated esophageal atresia (Gross type A), Dandy-Walker malformation, right microphthalmia, left coloboma, overlapping fingers, pleurocentrum in the thoracic vertebrae, reduced anogenital distance, and hearing loss. Her karyotype was diagnosed as 46,XX,del(13)(q32.1-qter) by amniocentesis, but array comparative genomic hybridization after birth revealed the deletion of 13q31.3-qter. At 48 days after birth, the infant underwent surgery for esophageal atresia and was later discharged from the hospital at 7 months of age.

CONCLUSION

This case report and the literature reviews supports the previous findings on the pathological roles of haploinsufficiency of the ZIC2/ZIC5 in Dandy-Walker malformation and the EFBN2 haploinsufficiency in eye malformation and hearing loss. Furthermore, the possible involvement of IRS2, COLA1, and COLA2 in eye malformation were identified. This is the first case of 13q deletion syndrome with esophageal atresia (Gross A), but it may be a symptom of VATER/VACTER association (vertebral defects, anorectal malformations, cardiac defects, tracheoesophageal fistula with or without esophageal atresia, renal malformations, and limb defects), as in the previous cases. These symptoms might also be associated with EFBN2 haploinsufficiency, although further research is required.

A rare unbalanced translocation (trisomy 5q33.3-qter, monosomy 13q34-qter) results in growth hormone deficiency and brain anomalies

Background

Unbalanced translocations between the q arm of chromosomes 5 and 13 are exceedingly rare and there is only one reported case with distal trisomy 5q/monosomy 13q. In this report, we describe a second patient with a similar rearrangement arising from a paternal balanced translocation.

Methods

Karyotype analysis was performed on the proband and their parents. Microarray was also conducted on the proband.

Results

Our patient was found to have global developmental delay, distinct facial features, short stature, growth hormone deficiency, delayed puberty, and brain anomalies including a small pituitary. Karyotype and microarray analysis revealed a terminal duplication of chromosome regions 5q33.3 to 5qter and a terminal deletion of chromosome regions 13q34 to 13qter that resulted from a balanced translocation in her father. The endocrine abnormalities and neuroimaging findings have not been previously described in patients with either copy number change.

Conclusions

This case helps expand on the phenotype of patients with distal trisomy 5q/monosomy 13q as well as possibly providing useful information on the more common individual copy number changes.

The Role of De Novo Variants in Formation of Human Anorectal Malformations

Anorectal malformations (ARM) represent a rare birth defect of the hindgut that occur in approximately 1 in 3000 live births. Around 60% of ARM occur with associated anomalies including defined genetic syndromes and associations with chromosomal aberrations. The etiology of ARM is heterogeneous, with the individual environmental or genetic risk factors remaining unknown for the majority of cases. The occurrence of familial ARM and previous epidemiologic analysis suggest autosomal dominant inheritance in a substantial subset of ARM patients. The implicated mortality and reduced fecundity in patients with ARM would lead to allele loss. However, mutational de novo events among the affected individuals could compensate for the evolutionary pressure. With the implementation of exome sequencing, array-based molecular karyotyping and family-based rare variant analyses, the technologies are available to identify the respective factors. This review discusses the identification of disease-causing variants among individuals with ARM. It highlights the role of mutational de novo events.

Retinoblastoma management in 13q deletion syndrome patients using super-selective chemotherapies and other cancer-directed interventions

BACKGROUND

This study aimed to identify best practices for treating 13q deletion syndrome (13q-) patients with retinoblastoma in the era of super-selective ophthalmic artery chemosurgery (OAC) and intravitreal injection therapy (IVIT).

METHODS

Retrospective study of 21 eyes from 14 patients with retinoblastoma and 13q- who were treated at Memorial Sloan Kettering Cancer Center (MSKCC) between May 2006 and May 2020, with a mean follow up of 3.7 years. Ocular survival, patient survival, and treatment toxicities were assessed.

RESULTS

Nine of the 12 eyes that underwent OAC/IVIT at MSKCC have been progression free for at least 1 year since their last treatments. Fifteen out of 26 OAC cycles resulted in grade 3-4 hematologic toxicity. There was one death from sepsis in the setting of intravenous chemotherapy (IVC) for metastatic disease that occurred after OAC/IVIT therapy. The 2-year Kaplan-Meier ocular survival estimate for the whole cohort was 75% and for the eyes that received OAC or IVIT at MSKCC 83%. For OAC hematologic toxicities, one platelet transfusion and two filgrastim doses were administered, and one patient was hospitalized for neutropenic fevers.

CONCLUSIONS

The majority of 13q- eyes treated with OAC/IVIT-based regimens can be cured, and there were no deaths related to complications from OAC or IVIT. 13q- Patients did have increased risk of systemic treatment complications, even from super-selective chemotherapies. Despite these toxicities, only one patient developed febrile neutropenia, one patient required a blood product transfusion, and two patients received filgrastim for both OAC and IVC complications. PRÉCIS: Children with 13q deletion syndrome with retinoblastoma managed with intra-arterial and intravitreal chemotherapy have excellent patient and ocular survival with acceptable toxicity.

Spread of X-chromosome inactivation into autosomal regions in patients with unbalanced X-autosome translocations and its phenotypic effects

Patients with unbalanced X-autosome translocations are rare and usually present a skewed X-chromosome inactivation (XCI) pattern, with the derivative chromosome being preferentially inactivated, and with a possible spread of XCI into the autosomal regions attached to it, which can inactivate autosomal genes and affect the patients' phenotype. We describe three patients carrying different unbalanced X-autosome translocations, confirmed by G-banding karyotype and array techniques. We analyzed their XCI pattern and inactivation spread into autosomal regions, through HUMARA, ZDHHC15 gene assay and the novel 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, and identified an extremely skewed XCI pattern toward the derivative chromosomes for all the patients, and a variable pattern of late-replication on the autosomal regions of the derivative chromosomes. All patients showed phenotypical overlap with patients presenting deletions of the autosomal late-replicating regions, suggesting that the inactivation of autosomal segments may be responsible for their phenotype. Our data highlight the importance of the XCI spread into autosomal regions for establishing the clinical picture in patients carrying unbalanced X-autosome translocations, and the incorporation of EdU as a novel and precise tool to evaluate the inactivation status in such patients.

A novel phenotype of 13q12.3 microdeletion characterized by epilepsy in an Asian child: a case report

Background

The microdeletion of chromosome 13 has been rarely reported. Here, we report a 14-year old Asian female with a de novo microdeletion on 13q12.3.

Case presentation

The child suffered mainly from two types of epileptic seizures: partial onset seizures and myoclonic seizures, accompanied with intellectual disability, developmental delay and minor dysmorphic features. The electroencephalogram disclosed slow waves in bilateral temporal, together with generalized spike-and-slow waves, multiple-spike-and-slow waves and slow waves in bilateral occipitotemporal regions. The exome sequencing showed no pathogenic genetic variation in the patient’s DNA sample. While the single nucleotide polymorphism (SNP) array analysis revealed a de novo microdeletion spanning 2.324 Mb, within the cytogenetic band 13q12.3.

Conclusions

The epilepsy may be associated with the mutation of KATNAL1 gene or the deletion unmasking a recessive mutation on the other allele, and our findings could provide a phenotypic expansion.

Terminal deletion of chromosome 13 in a fetus with normal NIPT: The added value of invasive prenatal diagnosis in the NIPT era

In the age of noninvasive prenatal testing, there is still an important role for invasive prenatal diagnosis, even for chromosomes 13, 18, and 21.

Reduced anogenital distance, hematuria and left renal hypoplasia in a patient with 13q33.1-34 deletion: case report and literature review

Background

13q33–q34 microdeletions are rare chromosomal aberrations associated with a high risk of developmental disability, facial dysmorphism, cardiac defects and other malformation of organs. It is necessary to collect and report evidence of this rare chromosome mutation to improve the prognosis of this rare disease.

Case presentation

We report a patient harboring an 11.56 Mb microdeletion at 13q33.1–34 region, which contains about 30 OMIM genes. Besides the common clinical manifestations such as facial dysmorphism, developmental delay, intellectual disability, epilepsy, and congenital heart disease, she also suffered from a reduced anogenital distance, hematuria and left renal hypoplasia. Most related cases were characterized by facial deformity and heart defects, but there were few reports on renal malformation, especially regarding renal hypoplasia with hematuria.

Conclusion

We have reported a patient suffering from a reduced anogenital distance, hematuria and left renal hypoplasia. A de novo 11.56 Mb deletion ranging from 13q33.1 to 13q34 (Chr13:103542220–115,106,996) was found by SNP-array analysis. It might be the first time for hematuria and renal hypoplasia to be reported as symptoms of 13q33-q34 deletion syndrome Neurodevelopmental disability, heart defects and urogenital/anorectal anomalies may be resulted from common or overlapping regions of deletion in chromosome bands 13q33.1-q34 and may share a common molecular mechanism.

Towards New Approaches to Evaluate Dynamic Mosaicism in Ring Chromosome 13 Syndrome

Individuals with ring chromosome 13 may show characteristics observed in a deletion syndrome and could present a set of dismorphies along with intellectual disability, according to chromosomal segments involved in the genetic imbalance. Nevertheless, ring anomalies likewise is called "dynamic mosaicism", phenomena triggered by the inner instability concerning the ring structure, thus leading to the establishment of different cell clones with secondary aberrations. Phenotypic features, such as growth failure and other anomalies in patients with this condition have been associated with an inherent ring chromosome mitotic instability, while recent studies offer evidence on a role played by the differential loss of genes implicated in development. Here, we observed similar mosaicism rates and specific gene loss profile among three individuals with ring chromosome 13 using GTW-banding karyotype analyses along with FISH and CGH-array approaches. Karyotypes results were: patient 1-r(13)(p13q32.3), patient 2-r(13)(p11q33.3), and patient 3-r(13)(p12q31.1). Array-CGH has revealed qualitative genetic differences among patients in this study and it was elusive in precise chromosomal loss statement, ranging from 13 Mb, 6.8 Mb, and 30 Mb in size. MIR17HG and ZIC2 loss was observed in a patient with digital anomalies, severe growth failure, microcephaly and corpus callosum agenesis while hemizygotic EFNB2 gene loss was identified in two patients, one of them with microphtalmia. According to these findings, it can be concluded that specific hemizygotic loss of genes related to development, more than dynamic mosaicism, may be causative of congenital anomalies shown in patients with ring 13 chromosome.

Bilateral Cleft Lip and Palate Accompanied by 13q- Syndrome with Deficiencies of FVII and FX: A Case Report

The 13q deletion syndrome is a rare genetic disorder caused by structural and functional monosomy of chromosome 13. On 13q34, which is the terminal of the long arm, causative genes of coagulation factors VII and X (FVII and FX) are mapped. Patients with a combination of FVII and FX deficiencies are extremely rare and there have been few articles about perioperative coagulation support for such patients. Herein, we report on a case of bilateral cleft lip and palate accompanied by 13q deletion syndrome with deficiencies of FVII and FX. The chromosomal investigation indicated 46, XX, del(13)(q33) by G-banding. Prothrombin time and activated partial thromboplastin time were found to be 21.0 seconds (sec) (prothrombin time-international normalized ratio 1.76) and 41.6 sec (normal range; 23.9 - 39.7 sec), respectively. The activities of coagulation FVII and FX were 22% and 36%, respectively. A two-stage cheiloplasty was performed at 4 and 7 months of age followed by a palatoplasty at 1 year and 6 months. Tranexamic acid was given intravenously three times a day for three days after each surgery. There were no adverse events such as bleeding from the oral or nasal cavities and healing of the surgical wound was good without dehiscence.

The rare 13q33-q34 microdeletions: eight new patients and review of the literature

The objective of this study is to shed light on the phenotype and inheritance pattern of rare 13q33-q34 microdeletions. Appropriate cases were retrieved using local databases of two largest Israeli centers performing CMA analysis. In addition, literature search in PubMed, DECIPHER and ClinVar databases was performed. Local database search yielded eight new patients with 13q33.1-q34 microdeletions (three of which had additional copy number variants). Combined with 15 cases detected by literature search, an additional 23 cases were reported in DECIPHER database, and 17 cases from ClinVar, so overall 60 patients with isolated 13q33.1-q34 microdeletions were described. Developmental delay and/or intellectual disability were noted in the vast majority of affected individuals (81.7% = 49/60). Of the 23 deletions involving the 13q34 cytoband only, in 3 cases, developmental delay and/or intellectual disability was not reported. Interestingly, in two of these cases (66.7%), the deletions did not involve the terminal CHAMP1 gene, as opposed to 3/20 (15%) of patients with 13q34 deletions and neurocognitive disability. Facial dysmorphism and microcephaly were reported in about half of the overall cases, convulsions were noted in one-fifth of the patients, while heart anomalies, short stature and hypotonia each involved about 10-30% of the cases. None of the 13q33-q34 deletions were inherited from a reported healthy parent. 13q33-q34 microdeletions are rare chromosomal aberrations, associated with high risk for neurodevelopmental disability. The rarity of this chromosomal aberration necessitates continuous reporting and collection of available evidence, to improve the ability to provide accurate genetic counseling, especially in the context of prenatal setting.

Deletion of Chromosome 13 due to Different Rearrangements and Impact on Phenotype

Patients with deletion of chromosome 13 present with variable clinical features, and the correlation between phenotype and genomic aberration is not well established in the literature, mainly due to variable sizes of the deleted segments and inaccuracy of breakpoint mapping. In order to improve the genotype-phenotype correlation, we obtained clinical and cytogenomic data from 5 Brazilian patients with different chromosome 13 deletions characterized by G-banding and array techniques. Breakpoints were nonrecurrent, with deletion sizes ranging from 3.8 to 43.3 Mb. Our patients showed some classic features associated with 13q deletion, independent of the location and size of the deletion: hypotonia, growth delay, psychomotor developmental delay, microcephaly, central nervous system anomalies, and minor facial dysmorphism as well as urogenital and limb abnormalities. Comparisons between the literature and our patients' data allowed us to narrow the critical regions that were previously reported for microphthalmia and urogenital abnormalities, indicating that gene haploinsufficiency of ARHGEF7, PCDH9 and DIAPH3, of MIR17HG and GPC6, and of EFNB2 may contribute to microcephaly, cardiovascular disease, and urogenital abnormalities, respectively. The knowledge about genes involved in the phenotypic features found in 13q deletion patients may help us to understand how the genes interact and contribute to their clinical phenotype, improving the patient's clinical follow-up.

A Rare Co-occurrence of Intestinal Malrotation and Hirschsprung's Disease in a Neonate with 13q21.31q33.1 Interstitial Deletion Including the EDNRB Gene

We report a rare co-occurrence of intestinal malrotation and Hirschsprung's disease (HSCR) in a male neonate with a large 38.8 Mb interstitial deletion of chromosome 13 extending from q21.31 to q33.1 including the EDNRB gene, who presented with craniofacial dysmorphic features and central nervous system malformations. The loss of EDNRB gene in addition to bilateral hearing loss and HSCR suggested an additional diagnosis of Waardenburg-Shah's syndrome. This case highlights the fact that prior knowledge of this rare association in infants with 13q deletion syndrome would enable early diagnosis and prompt interventions to prevent gastrointestinal complications.

Establishment of normative values for the fetal posterior fossa by magnetic resonance imaging

OBJECTIVE

Suspected Dandy-Walker continuum anomalies constitute a significant percentage of prenatal cases evaluated by magnetic resonance imaging (MRI). To unify the description of posterior fossa malformations, we sought to establish objective measurements for the posterior fossa in normal fetuses between 18 and 37 weeks gestation.

METHODS

T2-weighted images of normal fetal brains in sagittal projection were obtained from fetal magnetic resonance (MR) studies of normal brains performed from 2009 to 2017.121 fetal brains were included in the analysis. Three radiologists reviewed images and recorded the following for each case: superior posterior fossa angle (SPFA), posterior fossa perimeter, and tegmento-vermian angle (TVA).

RESULTS

For each feature, the mean of the measurements, the percentage of absolute difference of the reader measurement compared with mean measurement, and the interclass correlation (ICC) were calculated. Values are reported as mean ± standard deviation. Perimeter increases linearly with age, whereas the SPFA and the TVA are independent of gestational age. For all included cases, the SPFA averaged 100.9° ± 8° and the TVA averaged 2.5° ± 2.3°.

CONCLUSION

The superior posterior fossa angle, a novel measurement, and the posterior fossa perimeter can be used for establishing the expected size of the posterior fossa in second- and third-trimester fetuses by MRI.

13q mosaic deletion including RB1 associated to mild phenotype and no cancer outcome - case report and review of the literature

Background

The 13q deletion syndrome is a rare chromosome disorder associated with wide phenotypic spectrum, which is related to size and location of the deleted region and includes intellectual disability, growth retardation, craniofacial dysmorphisms, congenital malformations, and increased risk of retinoblastoma.

Case presentation

Here, we report on a teenage boy with a mild phenotype characterized by obesity, hyperactivity, dysphagia, dysgraphia, sleep disturbance, and minor dysmorphic features (round face, bushy eyebrows, and stubby hands). Array Comparative Genomic Hybridization on blood identified a mosaic 13q14.13-13q31.1 deletion, with a mosaicism rate around 40%, which was confirmed by quantitative PCR and interphase Fluorescent In Situ Hybridization (iFISH) on both blood genomic DNA and cultured/uncultured blood lymphocytes, respectively. Conversely, karyotype analysis on blood estimated a mosaicism rate of 24% and iFISH on buccal smears revealed a borderline value of 0.4%, suggesting the absence of 13q deletion in this cell line.

Conclusions

The comparison with previous patients carrying similar deletions informed that the proband clinical presentation is the mildest reported to date, thus supporting the burden of mosaicism in modulating the phenotype also in case of large chromosomal rearrangements. Characterization of further cases by in-depth mosaicism rate in tissues with different embryonic origins might contribute in the future to a better definition of genotype-phenotype correlation, including tumor risk.

Catatonia in Children and Adolescents: A High Rate of Genetic Conditions

Pediatric catatonia is a rare and severe neuropsychiatric syndrome. We previously reported, in 58 children and adolescents with catatonia, a high prevalence (up to 20%) of medical conditions, some of which have specific treatments.¹ Here we extend the cohort inclusion and report the first systematic molecular genetic data for this syndrome. Among the 89 patients consecutively admitted for catatonia (according to the pediatric catatonia rating scale)² between 1993 and 2014, we identify 51 patients (57.3%) who had genetic laboratory testing, of whom 37 had single nucleotide polymorphism (SNP) microarray tests for CNVs and 14 had routine genetic explorations (karyotyping and searches for specific chromosomal abnormalities by fluorescence in situ hybridization [FISH]) or a specific diagnosis test based on clinical history. To assess the causality of observed genetic findings in each patient, we used a causality assessment score (CAUS)³ including 5 causality-support criteria on a 3-point scale (0 = absent; 1 = moderate; 2 = high): the existence of similar cases in the literature; the presence of a clinical contributing factor; the presence of a biological contributing factor; the presence of other paraclinical symptoms; and response to a specific treatment related to the suspected genetic or medical condition.

Conventional Chromosome Analysis of Fetuses with Central Nervous System Anomalies and Associated Anomalies: Is Anything Changed?

Central nervous system (CNS) abnormalities are often isolated but can accompany various genetic syndromes. In this study, we evaluated conventional karyotype results and associated findings of fetuses that were diagnosed with CNS abnormalities. Cases included in the study were diagnosed with fetal CNS anomalies and underwent conventional karyotyping. Conventional karyotype results of subjects were compared with karyotype results of fetal karyotyped patients as a result of maternal anxiety in a two-year period. In this period, 69 patients were diagnosed with fetal CNS anomalies and 64 of them underwent invasive fetal karyotyping. Of these, 32 patients had isolated CNS anomalies, while 32 were associated with other anomalies. There was no significant difference between karyotype results when compared with the control group (p = 0.76). Apart from some specific anomalies, the aneuploidy rate does not significantly differ between fetuses with CNS anomalies and the control group. Advanced genetic evaluation may provide additional diagnostic benefits, especially for this group.

Chromosome 13q deletion syndrome involving 13q31‑qter: A case report

Partial deletions on the long arm of chromosome 13 lead to a number of different phenotypes depending on the size and position of the deleted region. The present study investigated 2 patients with 13q terminal (13qter) deletion syndrome, which manifested as anal atresia with rectoperineal fistula, complex type congenital heart disease, esophageal hiatus hernia with gastroesophageal reflux, facial anomalies and developmental and mental retardation. Array comparative genomic hybridization identified 2 regions of deletion on chromosome 13q31‑qter; 20.38 Mb in 13q31.3‑qter and 12.99 Mb in 13q33.1‑qter in patients 1 and 2, respectively. Comparisons between the results observed in the present study and those obtained from patients in previous studies indicate that the gene encoding ephrin B2 (EFNB2) located in the 13q33.3‑q34 region, and the gene coding for endothelin receptor type B, in the 13q22.1‑31.3 region, may be suitable candidate genes for the observed urogenital/anorectal anomalies. In addition, the microRNA‑17‑92a‑1 cluster host gene and the glypican 6 gene in the 13q31.3 region, as well as EFNB2 and the collagen type IV a1 chain (COL4A1) and COL4A2 genes in the 13q33.1‑q34 region may together contribute to cardiovascular disease development. It is therefore possible that these genes may be involved in the pathogenesis of complex type congenital heart disease in patients with 13q deletion syndrome.

De novo large rare copy-number variations contribute to conotruncal heart disease in Chinese patients

Conotruncal heart anomalies (CTDs) are particularly prevalent congenital heart diseases (CHD) in Hong Kong. We surveyed large (>500 kb), rare (<1% frequency in controls) copy-number variations (CNVs) in Chinese patients with CTDs to identify potentially disease-causing variations. Adults who tested negative for 22q11.2 deletions were recruited from the adult CHD clinic in Hong Kong. Using a stringent calling criteria, high-confidence CNV calls were obtained, and a large control set comprising 3,987 Caucasian and 1,945 Singapore Chinese subjects was used to identify rare CNVs. Ten large rare CNVs were identified, and 3 in 108 individuals were confirmed to harbour de novo CNVs. All three patients were syndromic with a more complex phenotype, and each of these CNVs overlapped regions likely to be important in CHD. One was a 611 kb deletion at 17p13.3, telomeric to the Miller-Dieker syndrome (MDS) critical region, overlapping the NXN gene. Another was a 5 Mb deletion at 13q33.3, within a previously described critical region for CHD. A third CNV, previously unreported, was a large duplication at 2q22.3 overlapping the ZEB2 gene. The commonly reported 1q21.1 recurrent duplication was not observed in this Chinese cohort. We provide detailed phenotypic and genotypic descriptions of large rare genic CNVs that may represent CHD loci in the East Asian population. Larger samples of Chinese origin will be required to determine whether the genome-wide distribution differs from that found in predominantly European CHD cohorts.

Cytogenetic Studies of Rwandan Pediatric Patients Presenting with Global Developmental Delay, Intellectual Disability and/or Multiple Congenital Anomalies

Global developmental delay (GDD) is defined as a significant delay in two or more developmental domains: gross or fine motor, speech/language, cognitive, social/personal and activities of daily living. Many of these children will go on to be diagnosed with intellectual disability (ID), which is most commonly defined as having an IQ <75 in addition to impairment in adaptive functioning. Cytogenetic studies have been performed in 664 Rwandan pediatric patients presenting GDD/ID and/or multiple congenital abnormalities (MCA). Karyotype analysis was performed in all patients and revealed 260 chromosomal abnormalities. The most frequent chromosomal abnormality was Down syndrome and then Edward syndrome and Patau syndrome. Other identified chromosomal abnormalities included 47,XX,+del(9)(q11), 46,XY,del(13)(q34) and 46,XX,der(22)t(10;22)(p10;p10)mat. In conclusion, our results highlight the high frequency of cytogenetically detectable abnormalities in this series, with implications for the burden on the healthcare. This study demonstrates the importance of cytogenetic analysis in patients with GDD/ID and MCA.

Cryptic 13q34 and 4q35.2 Deletions in an Italian Family

Variations of DNA sequences in the human genome range from large, microscopically visible chromosome anomalies to single nucleotide changes. Submicroscopic genomic copy number variations, i.e. chromosomal imbalances which are undetectable by conventional cytogenetic analysis, play an intriguing clinical role. In this study, we describe the clinical consequences of the concurrent presence of an interstitial deletion in 13q34 and a terminal deletion in 4q35.2 in an Italian family. The index patient, a 19-year-old male, as well as his 12-year-old sister are carriers of both deletions, one of maternal and the other of paternal origin. The phenotype includes language delay, multiorgan involvement and bleeding diathesis with mild deficiency of factors X and VII. In the sister, the concomitant presence of Noonan syndrome may partly explain the clinical symptoms. The deleted region on chromosome 13 involves several genes (ATP11A, MCF2L, F7, F10, PROZ, PCID2, CUL4A, and LAMP1); some of these seem to play a role in the proband's phenotype. The terminal deletion in 4q35.2 contains other OMIM genes (FRG1, FRG2 and DBET); moreover, the 4q region is reported as a susceptibility locus for Crohn's disease, diagnosed in the proband's father. To our knowledge, this is the first report of a family with these 2 submicroscopic copy number changes. We tried to relate the clinical phenotype of the proband and his family to the molecular function of the involved genes.

Acquired retinal pigmentary degeneration in a child with 13q deletion syndrome

Orbeli syndrome, or 13q deletion syndrome, is a rare condition caused by a distal deletion in the long arm of chromosome 13. The syndrome is characterized by severe physical malformations and developmental delays and has been associated with numerous ocular manifestations. We report the case of a 10-year-old boy with 13q deletion syndrome, who was evaluated for impaired vision and found to have bilateral retinal pigmentary changes resembling those seen in retinitis pigmentosa. There has only been one other case of retinal pigment variation in association with 13q deletion syndrome; however, this represents the first case of bilateral symmetric retinal pigmentary changes with corresponding rod and cone dysfunction on electroretinography.

Holoprosencephaly with cerebellar vermis hypoplasia in 13q deletion syndrome: Critical region for cerebellar dysgenesis within 13q32.2q34

We describe two unrelated patients with terminal deletions in the long arm of chromosome 13 showing brain malformation consisting of holoprosencephaly and cerebellar vermis hypoplasia. Array comparative genomic hybridization analysis revealed a pure terminal deletion of 13q31.3q34 in one patient and a mosaic ring chromosome with 13q32.2q34 deletion in the other. Mutations in ZIC2, located within region 13q32, cause holoprosencephaly, whereas the 13q32.2q32.3 region is associated with cerebellar vermis hypoplasia (Dandy-Walker syndrome). The rare concurrence of these major brain malformations in our patients provides further evidence that 13q32.2q32.3 deletion, harboring ZIC2 and ZIC5, leads to cerebellar dysgenesis.

11p15 duplication and 13q34 deletion with Beckwith-Wiedemann syndrome and factor VII deficiency

Here we report a patient with 11p15.4p15.5 duplication and 13q34 deletion presenting with Beckwith-Wiedemann syndrome (BWS) and moderate deficiency of factor VII (FVII). The duplication was initially diagnosed on methylation-sensitive multiplex ligation-dependent probe amplification. Array comparative genome hybridization confirmed its presence and indicated a 13q34 distal deletion. The patient's clinical symptoms, including developmental delay and facial dysmorphism, were typical of BWS with paternal 11p15 trisomy. Partial 13q monosomy in this patient is associated with moderate deficiency of FVII and may also overlap with a few symptoms of paternal 11p15 trisomy such as developmental delay and some facial features. To our knowledge this is the first report of 11p15.4p15.5 duplication associated with deletion of 13q34 and FVII deficiency. Moreover, this report emphasizes the importance of detailed clinical as well as molecular examinations in patients with BWS features and developmental delay.

De Novo interstitial deletion 13q33.3q34 in a male patient with double outlet right ventricle, microcephaly, dysmorphic craniofacial findings, and motor and developmental delay

We describe a 6-year-old male, diagnosed at birth with double outlet right ventricle (DORV), anterior aorta, multiple ventricular septal defects, pulmonary stenosis, microcephaly and mildly dysmorphic craniofacial findings. Chromosomal analysis showed a normal male karyotype but on subsequent array comparative genomic hybridization (array CGH) analysis a de novo 2.5 Mb loss in chromosome 13q at 13q33.3q34, together with an inherited gain at 4p12, were detected. The propositus underwent placement of a Blalock Taussig shunt and subsequently a Glenn and Fontan operation was performed. In this report we propose that COL4A1 and COL4A2 may be candidate genes for congenital heart disease (CHD) in individuals with a deletion in 13q within the 6Mb critical region for cardiac development proposed by Huang et al., [2012].

Neural Tube Defects: The Experience of the Registry of Congenital Malformations of Alsace, France, 1995-2009

Context and Objective: Considering the lack of accurate and up-to-date information available about neural tube defects (NTDs) in France, the purpose of this study was to review clinical and epidemiological data of NTDs and to evaluate the current efficiency of prenatal diagnosis in Alsace (northeastern France). Methods: A population-based retrospective study was performed from data of the Registry of Congenital Malformations of Alsace between 1995 and 2009. Data were analyzed as a whole and according to the anatomical type of the malformation (anencephaly, cephalocele and spina bifida). Statistical analyses were carried out using the Statistical Package for the Social Sciences. Results: 272 NTDs were recorded divided in 113 cases of anencephaly (42%), 35 cases of cephalocele (13%) and 124 cases of spina bifida (45%). The total prevalence at birth of 14/10,000 (95% CI 13-16) was stable throughout the reporting period. A chromosome abnormality was identified in 27 cases (12% of all karyotyped cases). NTDs were prenatally diagnosed by ultrasound in 88% of the cases. The mean age upon prenatal diagnosis slightly declined during the 15-year period, significantly for spina bifida only. The global rate of terminations of pregnancy following prenatal diagnosis was 97% (230/238). Conclusion: This work constitutes a unique population-based study providing accurate and specific up-to-date data from a unique center over a longer period (1995-2009). The most important information concerns the high and stable prevalence, which calls into question the efficiency of the primary prevention by folic acid supplementation and the efficiency of prenatal diagnosis.

Developmental and adaptive functioning in children with retinoblastoma: a longitudinal investigation

PURPOSE

To determine the developmental trajectory of early cognitive and adaptive skills in young children with retinoblastoma from diagnosis to 5 years of age.

PATIENTS AND METHODS

Ninety-four patients with retinoblastoma treated according to an institutional protocol underwent serial assessments of cognitive and adaptive functioning at age 6 months and 1, 2, 3, and 5 years. Data were analyzed by treatment strata, with patients with 13q deletion analyzed separately.

RESULTS

At baseline, across all patients (except those with 13q deletion), developmental functioning was comparable with the normative mean, with mean scores for all strata within the average range. However, at age 5 years, developmental functioning was in the low average range and significantly below normative means. The trajectories of developmental functioning demonstrated significant decline over time, although this varied by treatment group/strata. Patients treated with enucleation only evidenced the greatest decline in cognitive functioning; significant change was not observed in patients treated with other modalities. Notable declines in parent-reported communication skills were observed in the majority of patients. Patients with 13q deletion evidenced delayed cognitive functioning at baseline, but minimal declines were observed through age 3 years. However, significant decreases in adaptive functioning were demonstrated over time for the 13q deletion subset.

CONCLUSION

The declines in functioning observed in this study were unexpected, as was the poorer performance of the enucleation-only group. This highlights the necessity of continuing to assess cognitive functioning in patients with retinoblastoma as they age. Additional research is necessary to determine the long-term trajectory of cognitive development in this population.

Inversion duplication deletions involving the long arm of chromosome 13: phenotypic description of additional three fetuses and genotype-phenotype correlation

Inversion duplication and terminal deletion of the long arm of chromosome 13 (inv dup del 13q) is a rare chromosomal rearrangement: only five patients have been reported, mostly involving a ring chromosome 13. We report on additional three fetuses with pure inv dup del 13q: Patient 1 had macrosomia, enlarged kidneys, hypersegmented lungs, unilateral moderate ventriculomegaly, and a mild form of hand and feet preaxial polydactyly; Patient 2 had intrauterine growth retardation, widely spaced eyes, left microphthalmia, right anophthalmia, short nose, bilateral absent thumbs, cutaneous syndactyly of toes 4 and 5, bifid third metacarpal, a small left kidney, hyposegmented lungs, and partial agenesis of the corpus callosum; Patient 3 had widely spaced eyes, long and smooth philtrum, low-set ears, median notch in the upper alveolar ridge, bifid tongue, cutaneous syndactyly of toes 2 and 3, enlarged kidneys and pancreas, arhinencephaly, and partial agenesis of the corpus callosum. We compared the phenotypes of these patients to those previously reported for ring chromosome 13, pure 13q deletions and duplications. We narrowed some critical regions previously reported for lung, kidney and fetal growth, and for thumb, cerebral, and eye anomalies.

The sodium leak channel, NALCN, in health and disease

Ion channels are crucial components of cellular excitability and are involved in many neurological diseases. This review focuses on the sodium leak, G protein-coupled receptors (GPCRs)-activated NALCN channel that is predominantly expressed in neurons where it regulates the resting membrane potential and neuronal excitability. NALCN is part of a complex that includes not only GPCRs, but also UNC-79, UNC-80, NLF-1 and src family of Tyrosine kinases (SFKs). There is growing evidence that the NALCN channelosome critically regulates its ion conduction. Both in mammals and invertebrates, animal models revealed an involvement in many processes such as locomotor behaviors, sensitivity to volatile anesthetics, and respiratory rhythms. There is also evidence that alteration in this NALCN channelosome can cause a wide variety of diseases. Indeed, mutations in the NALCN gene were identified in Infantile Neuroaxonal Dystrophy (INAD) patients, as well as in patients with an Autosomal Recessive Syndrome with severe hypotonia, speech impairment, and cognitive delay. Deletions in NALCN gene were also reported in diseases such as 13q syndrome. In addition, genes encoding NALCN, NLF- 1, UNC-79, and UNC-80 proteins may be susceptibility loci for several diseases including bipolar disorder, schizophrenia, Alzheimer's disease, autism, epilepsy, alcoholism, cardiac diseases and cancer. Although the physiological role of the NALCN channelosome is poorly understood, its involvement in human diseases should foster interest for drug development in the near future. Toward this goal, we review here the current knowledge on the NALCN channelosome in physiology and diseases.

A newly recognized 13q12.3 microdeletion syndrome characterized by intellectual disability, microcephaly, and eczema/atopic dermatitis encompassing the HMGB1 and KATNAL1 genes

Proximal deletions of the long arm of chromosome 13 have been reported only rarely. Here we present three unrelated patients with heterozygous, apparently de novo deletions encompassing 13q12.3. The patients present with moderate demonstrated or apparent intellectual disability, postnatal microcephaly, and eczema/atopic dermatitis as the predominant symptoms. In addition, they had pronounced feeding difficulties in early infancy. They displayed similar facial features such as malar flattening, a prominent nose with underdeveloped alae nasi, a smooth philtrum, and a thin vermillion of the upper lip. The proximal and distal breakpoints were clustered and the deletions spanned from 1.4 to 1.7 Mb, comprising at least 11 RefSeq genes. However, heterozygous deletions partially overlapping those observed in the present patients have been described in healthy parents of patients with Peters-Plus syndrome, an autosomal recessive disorder caused by inactivation of the B3GALTL gene. We therefore propose that the critical region of the 13q12.3 microdeletion syndrome contains only three genes, namely, KATNAL1, HMGB1, and LINC00426, a non-protein coding RNA. The KATNAL1 protein belongs to a family of microtubule severing enzymes that have been implicated in CNS plasticity in experimental models, but little is known about its function in humans. The HMGB1 protein is an evolutionarily conserved chromatin-associated protein involved in many biologically important processes. In summary, we propose that microdeletion 13q12.3 represents a novel clinically recognizable condition and that the microtubule severing gene KATNAL1 and the chromatin-associated gene HMGB1 are candidate genes for intellectual disability inherited in an autosomal dominant pattern.

De novo 13q13.3-21.31 deletion involving RB1 gene in a patient with hemangioendothelioma of the liver

Interstitial deletions of the long arm of chromosome 13 (13q) are related with variable phenotypes, according to the size and the location of the deleted region. The main clinical features are moderate/severe mental and growth retardation, cranio-facial dysmorphism, variable congenital defects and increased susceptibility to tumors. Here we report a 3-year-old girl carrying a de novo 13q13.3-21.32 interstitial deletion. She showed developmental delay, growth retardation and mild dysmorphism including curly hair, high forehead, short nose, thin upper lip and long philtrum. An abnormal mass was surgically removed from her liver resulting in a hemangioendothelioma. Array analysis allowed us to define a deleted region of about 27.87 Mb, which includes the RB1 gene. This is the first report of a 13q deletion associated with infantile hemangioendothelioma of the liver.

Clinical utility of multiplex ligation-dependent probe amplification technique in identification of aetiology of unexplained mental retardation: a study in 203 Indian patients

BACKGROUND & OBJECTIVES

Developmental delay (DD)/mental retardation also described as intellectual disability (ID), is seen in 1-3 per cent of general population. Diagnosis continues to be a challenge at clinical level. With the advancement of new molecular cytogenetic techniques such as cytogenetic microarray (CMA), multiplex ligation-dependent probe amplification (MLPA) techniques, many microdeletion/microduplication syndromes with DD/ID are now delineated. MLPA technique can probe 40-50 genomic regions in a single reaction and is being used for evaluation of cases with DD/ID. In this study we evaluated the clinical utility of MLPA techniques with different probe sets to identify the aetiology of unexplained mental retardation in patients with ID/DD.

METHODS

A total of 203 randomly selected DD/ID cases with/without malformations were studied. MLPA probe sets for subtelomeric regions (P070/P036) and common microdeletions/microduplications (P245-A2) and X-chromosome (P106) were used. Positive cases with MLPA technique were confirmed using either fluorescence in situ hybridization (FISH) or follow up confirmatory MLPA probe sets.

RESULTS

The overall detection rate was found to be 9.3 per cent (19 out of 203). The detection rates were 6.9 and 7.4 per cent for common microdeletion/microduplication and subtelomeric probe sets, respectively. No abnormality was detected with probe set for X-linked ID. The subtelomeric abnormalities detected included deletions of 1p36.33, 4p, 5p, 9p, 9q, 13q telomeric regions and duplication of 9pter. The deletions/duplications detected in non telomeric regions include regions for Prader Willi/Angelman regions, Williams syndrome, Smith Magenis syndrome and Velocardiofacial syndrome.

INTERPRETATION & CONCLUSIONS

Our results show that the use of P245-A2 and P070/P036-E1 probes gives good diagnostic yield. Though MLPA cannot probe the whole genome like cytogenetic microarray, due to its ease and relative low cost it is an important technique for evaluation of cases with DD/ID.

Partial trisomy 7q and monosomy 13q in a child with disorder of sex development: phenotypic and genotypic findings

Terminal 7q duplication and terminal 13q deletion are two conditions with variable phenotypes including microcephaly, thumb a-/hypoplasia, cortical dysplasia, microphtalmia, intellectual disability and dysmorphic features. We describe a boy born to a mother with a reciprocal t (7;13) who combines both a terminal 7q33-qter duplication and terminal 13q33-qter deletion through the inheritance of a derivative chromosome 13 (der (13)). The patient presented with developmental delay, facial and non-facial dysmorphic features, hypertonia, genital abnormality and skeletal malformation but no thumb a-/hypoplasia or microphtalmia. Knowing the exact breakpoints of his chromosomal aberrations using high resolution array CGH (aCGH) and comparison of his phenotypes with those of 24 and 59 previously published cases of 7q duplication and 13q deletion, respectively, allow us to further narrow the size of the proposed critical regions for microcephaly, thumb a-/hypoplasia and hypo/hypertonia on chromosome 13.

Genome-wide copy number analysis uncovers a new HSCR gene: NRG3

Hirschsprung disease (HSCR) is a congenital disorder characterized by aganglionosis of the distal intestine. To assess the contribution of copy number variants (CNVs) to HSCR, we analysed the data generated from our previous genome-wide association study on HSCR patients, whereby we identified NRG1 as a new HSCR susceptibility locus. Analysis of 129 Chinese patients and 331 ethnically matched controls showed that HSCR patients have a greater burden of rare CNVs (p = 1.50×10⁻⁵), particularly for those encompassing genes (p = 5.00×10⁻⁶). Our study identified 246 rare-genic CNVs exclusive to patients. Among those, we detected a NRG3 deletion (p = 1.64×10⁻³). Subsequent follow-up (96 additional patients and 220 controls) on NRG3 revealed 9 deletions (combined p = 3.36×10⁻⁵) and 2 de novo duplications among patients and two deletions among controls. Importantly, NRG3 is a paralog of NRG1. Stratification of patients by presence/absence of HSCR–associated syndromes showed that while syndromic–HSCR patients carried significantly longer CNVs than the non-syndromic or controls (p = 1.50×10⁻⁵), non-syndromic patients were enriched in CNV number when compared to controls (p = 4.00×10⁻⁶) or the syndromic counterpart. Our results suggest a role for NRG3 in HSCR etiology and provide insights into the relative contribution of structural variants in both syndromic and non-syndromic HSCR. This would be the first genome-wide catalog of copy number variants identified in HSCR.

Copy number variations (CNVs) are significant genetic risk factors in disease pathogenesis and represent an important portion of missing heritability for some human diseases, making their discovery essential for the identification of genes and risk factors for a wide range of diseases, including Hirschsprung disease (HSCR, congenital colon aganglionosis). Since the discovery of the major HSCR gene, RET, a number of rare mutations have been reported in RET and other genes involved in the development of the enteric nervous system. However, these mutations contribute to only a small proportion of the disease susceptibility. Taking advantage of the recent technical and methodological advances, we have examined the contribution of CNVs to the disease. We have found that HSCR patients are enriched with CNVs encompassing genes. In particular, we found that deletions of NRG3, a paralog of the previously identified HSCR–susceptibility gene NRG1, were associated with the HSCR phenotype.

A case of del(13)(q14.2)(q31.3) associated with hypothyroidism, hypertriglyceridemia, hypercholesterolemia and total ophthalmoplegia

13q deletion syndrome is caused by the absence of a portion of the long arm of chromosome 13. This syndrome is a rare condition characterized by a wide range of clinical findings. Phenotype varies with the location and size of the deletion. We report a female dizygotic twin with a proximal deletion of 13q and failure to thrive, hypotonia, and multiple anomalies included pytosis and total ophthalmology at right side, strabismus at left, bilateral iris heterochromia and telecantus. She had a broad nasal bridge with flat philtrum, micrognathia and antevert ear lobes. Her umbilicus had vanished. Her left coxa was dislocated and left toes were overlapped. She was also found to have hypertriglyceridemia, hypercholesterolemia, and hypothyroidism. Chromosome analysis showed a proximal deletion of chromosome 13 [karyotype 46,XX,del(13) (q14.2q31.3)] which was confirmed by high-resolution microarray based comparative genomic hybridization. The described patient is unique among similar rare cases with different deletion breakpoints. It is the first case of 13q14.2q31.3 deletion where the breakpoints are clearly defined, indicating the importance of detailed clinical description and high-resolution genomic analysis for characterization of rare genetic syndromes.

13q deletion syndrome and retinoblastoma in identical dichorionic diamniotic monozygotic twins

PURPOSE

To report the case of identical dichorionic diamniotic female twins with unilateral retinoblastoma in 13q deletion syndrome.

METHODS

Clinical and ophthalmoscopic evaluation, combination of multiple ligation-dependent probe amplification, array-comparative genomic hybridization analyses, and magnetic resonance imaging were performed.

RESULTS

Peculiar facial features, marked hypotonia, gastroesophageal reflux, interatrial septal defect with left to right shunt and light dilatation of right chambers, 5th finger hypoplasia, 3rd-5th toes clinodactyly, 2nd toe overlapped to 3rd toe, and cutis marmorata were found. Ophthalmoscopic evaluation revealed unilateral retinoblastoma in both girls. Magnetic resonance imaging detected corpus callosum hypoplasia in both twins. A 34.4-Mb deletion involving bands 13q13.2-q21.33 and including the RB1 gene was identified in both twins. The deletion was not present in the DNA of their parents and older brother.

CONCLUSIONS

Dysmorphic features in children must be always suspicious of 13q deletion syndrome and a short ophthalmoscopic follow-up is necessary to detect the presence of a retinoblastoma.

Speech Pathology Services to Children With Cancer and Nonmalignant Hematological Disorders

Children with cancer and nonmalignant hematological disorders may require speech pathology (SP) support; however, limited evidence is available describing prevalence and severity of swallowing/feeding and communication impairments in this population. A retrospective chart review of 70 children referred to SP at the newly formed Queensland Children’s Cancer Centre was conducted to describe the prevalence and severity of swallowing/feeding and communication dysfunction, and the association between impairment, oncology and hematology diagnosis, and service utilization (time and occasions of service). Swallowing/feeding disorders were the most commonly observed impairments at initial assessment (58.6%). Children with central nervous system tumors ( P = .03) and nonmalignant hematological disorder ( P = .03) had significantly higher rates of feeding impairment than other oncology and hematology diagnostic groups. Children with central nervous system tumors had the highest rates of oral phase ( P = .01) and pharyngeal phase ( P = .01) dysphagia (swallowing disorder). No significant difference was found between diagnostic groups for intensity of SP service delivery. Prospective research is required to examine prevalence and severity of disorders, and service utilization in a more established clinic, and to investigate interactions between cancer treatment and swallowing/feeding and communication dysfunction.

Prenatal diagnosis of partial trisomy 3q resulting from t(3;14) in a fetus with multiple anomalies including vermian hypoplasia

While genetic origin of Dandy-Walker complex has not yet fully elucidated, the complex has been known to be associated with structural and chromosomal abnormalities. A partial trisomy 3q was also identified in patients with DWC. 3q duplication syndrome is defined as duplications of large parts of 3q, especially 3q21-qter. Most cases with 3q duplication are diagnosed postnatally and the patients show typical features including various facial dysmorphisms, congenital heart defects, genitourinary malformations, and mental and growth retardation. Here we report a 28 year old nulliparous woman who was referred from the infertility clinic at 21 gestational weeks. Fetal ultrasonographic examination showed various abnormal findings including a ventricular septal defect, hydrocephalus, and hypoplasia of the cerebellar vermis. Fetal chromosome analysis was initially reported as 46,XY,der(14)(?::p11.2→qter). Array CGH followed by FISH allowed precise characterization of the der(14) chromosome and the initial karyotype of the fetus had been changed to 46,XY,add(14)(p11).ish der(14)t(3;14)(q26.1;p11)(tel3q+).arr 3q26.1q29(166249469-199288361)x3. Though further studies are required, gene clusters rather than a single gene might be responsible for the clinical features of the Dandy-Walker complex.