Prenatal diagnosis of 13q- syndrome in a fetus with holoprosencephaly and thumb agenesis

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.

Cytogenomic Investigation of Syndromic Brazilian Patients with Differences of Sexual Development

BACKGROUND

Cytogenomic methods have gained space in the clinical investigation of patients with disorders/differences in sexual development (DSD). Here we evaluated the role of the SNP array in achieving a molecular diagnosis in Brazilian patients with syndromic DSD of unknown etiology.

METHODS

Twenty-two patients with DSD and syndromic features were included in the study and underwent SNP-array analysis.

RESULTS

In two patients, the diagnosis of 46,XX SRY + DSD was established. Additionally, two deletions were revealed (3q29 and Xp22.33), justifying the syndromic phenotype in these patients. Two pathogenic CNVs, a 10q25.3-q26.2 and a 13q33.1 deletion encompassing the FGFR2 and the EFNB2 gene, were associated with genital atypia and syndromic characteristics in two patients with 46,XY DSD. In a third 46,XY DSD patient, we identified a duplication in the 14q11.2-q12 region of 6.5 Mb associated with a deletion in the 21p11.2-q21.3 region of 12.7 Mb. In a 46,XY DSD patient with delayed neuropsychomotor development and congenital cataracts, a 12 Kb deletion on chromosome 10 was found, partially clarifying the syndromic phenotype, but not the genital atypia.

CONCLUSIONS

The SNP array is a useful tool for DSD patients, identifying the molecular etiology in 40% (2/5) of patients with 46,XX DSD and 17.6% (3/17) of patients with 46,XY DSD.

Prenatal Detection and Postnatal Follow-Up of Segmental Aneusomies of Chromosome 13 in 4 Consecutive Pregnancies in an Ethnic South Indian Family With a Maternally Inherited Balanced Translocation

OBJECTIVE

To assess the postnatal clinical manifestation of an antenatally detected unbalanced rearrangement involving chromosome 13 in an ethnic South Indian couple.

METHODS

We used conventional cytogenetics on fetal cells obtained from prenatal specimens and on peripheral blood lymphocytes from consanguineous family members to ascertain the chromosomal abnormalities.

RESULTS

We report the reproductive outcomes of a maternally inherited chromosome translocation involving chromosome 9 and 13 and the informed decisions of the couple, after genetic counseling in India, regarding their 4 pregnancies.

CONCLUSION

This case report highlights the current practice in India of offering prenatal diagnosis and preimplantation genetic diagnosis to individuals who are carriers of balanced translocations, to reduce the risk of conceiving chromosomally abnormal offspring.

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.

Interpretation of copy number alterations identified through clinical microarray-comparative genomic hybridization

Many copy number alterations (CNA) currently interpreted as variants of unknown significance (VUS) will ultimately be determined to be benign; however, their classification requires a more extensive characterization of the human genome than currently exists. There is no definitive set of rules or level of evidence required to define a CNA as benign. The information needed to accurately assess the pathogenic impact of CNA is beginning to be assembled. Although the lack of understanding of the human genome can make clinical array-comparative genomic hybridization interpretation frustrating, it is precisely why clinical human genetics is an exciting arena in which to work.

Genotype-phenotype correlations in patients with retinoblastoma and interstitial 13q deletions

Patients with an interstitial 13q deletion that contains the RB1 gene show retinoblastoma and variable clinical features. Relationship between phenotypic expression and loss of specific neighboring genes are unresolved, yet. We obtained clinical, cytogenetic and molecular data in 63 patients with an interstitial 13q deletion involving RB1. Whole-genome array analysis or customized high-resolution array analysis for 13q14.11q14.3 was performed in 38 patients, and cytogenetic analysis was performed in 54 patients. Deletion sizes ranged between 4.2 kb and more than 33.43 Mb; breakpoints were non-recurrent. Sequence analysis of deletion junctions in five patients revealed microhomology and insertion of 2-34 base pairs suggestive of non-homologous end joining. Milder phenotypic expression of retinoblastoma was observed in patients with deletions larger than 1 Mb, which contained the MED4 gene. Clinical features were compared between patients with small (within 13q14), medium (within 13q12.3q21.2) and large (within 13q12q31.2) deletions. Patients with a small deletion can show macrocephaly, tall stature, obesity, motor and/or speech delay. Patients with a medium deletion show characteristic facial features, mild to moderate psychomotor delay, short stature and microcephaly. Patients with a large deletion have characteristic craniofacial dysmorphism, short stature, microcephaly, mild to severe psychomotor delay, hypotonia, constipation and feeding problems. Additional features included deafness, seizures and brain and heart anomalies. We found no correlation between clinical features and parental origin of the deletion. Our data suggest that hemizygous loss of NUFIP1 and PCDH8 may contribute to psychomotor delay, deletion of MTLR1 to microcephaly and loss of EDNRB to feeding difficulties and deafness.

Prenatal diagnosis of a case of partial monosomy/monosomy 13 mosaicism: 46,XX,r(13)(p11q33)/45,XX,-13 suspected by nuchal fold translucency increasing

Large numbers of patients with deletions of the long arm of chromosome 13 have been described. However, only a few instances have been reported of monosomy 13/r(13) mosaicism. A 31-year-old Japanese woman underwent an ultrasound tomographic screening, which detected a fetus with a nuchal translucency (NT) of >5.8mm, indicating an increased risk of fetal chromosomal abnormality. An amniocentesis (AC) was performed, and the karyotype was 46,XX,r(13)(p11q33)[18] / 45XX[12]. Ultrasound showed echogenic skin edema. Phenotype of the fetus after delivery revealed some anomalies, including hyponasal bridge, hypertelorism, ambiguous genitalia with huge clitoris, low-set ear, neck edema and webbing.Deletion of the long arm of chromosome 13 is associated with a wide spectrum of abnormalities, including retinoblastoma, mental and growth retardation, brain malformations, heart defects, distal limb deformities, and digestive, urogenital, and other abnormalities. The present case, however, had anomalies which were too faint to be detected by ultrasound tomography. Prenatal diagnosis of deletion 13q syndrome is rare. A number of reports have documented an association between increased NT and chromosomal defects. Ultrasound did not identify any major anomaly in this case, however amniocentesis was able to detect this rare abnormality.

Amelia, cleft lip, and holoprosencephaly: a distinct entity

We report on a male fetus with amelia, cleft lip, and holoprosencephaly. We compare the clinical findings in our patient with those of previously reported cases with the most clinical overlap. To date only four cases with bilateral limb amelia, CNS anomalies, and facial clefts have been described. Our report appears to represent the fifth case with such a combination of anomalies.

Mutations in ZIC2 in human holoprosencephaly: description of a novel ZIC2 specific phenotype and comprehensive analysis of 157 individuals

BACKGROUND

Holoprosencephaly (HPE), the most common malformation of the human forebrain, may be due to mutations in genes associated with non-syndromic HPE. Mutations in ZIC2, located on chromosome 13q32, are a common cause of non-syndromic, non-chromosomal HPE.

OBJECTIVE

To characterise genetic and clinical findings in patients with ZIC2 mutations.

METHODS

Through the National Institutes of Health and collaborating centres, DNA from approximately 1200 individuals with HPE spectrum disorders was analysed for sequence variations in ZIC2. Clinical details were examined and all other known cases of mutations in ZIC2 were included through a literature search.

RESULTS

By direct sequencing of DNA samples of an unselected group of unrelated patients with HPE in our NIH laboratory, ZIC2 mutations were found in 8.4% (49/582) of probands. A total of 157 individuals from 119 unrelated kindreds are described, including 141 patients with intragenic sequence determined mutations in ZIC2. Only 39/157 patients have previously been clinically described. Unlike HPE due to mutations in other genes, most mutations occur de novo and the distribution of HPE types differs significantly from that of non-ZIC2 related HPE. Evidence is presented for the presence of a novel facial phenotype which includes bitemporal narrowing, upslanting palpebral fissures, a short nose with anteverted nares, a broad and well demarcated philtrum, and large ears.

CONCLUSIONS

HPE due to ZIC2 mutations is distinct from that due to mutations in other genes. This may shed light on the mechanisms involved in formation of the forebrain and face and will help direct genetic counselling and diagnostic strategies.

Phenotype and 244k array-CGH characterization of chromosome 13q deletions: an update of the phenotypic map of 13q21.1-qter

Partial deletions of the long arm of chromosome 13 lead to variable phenotypes dependant on the size and position of the deleted region. In order to update the phenotypic map of chromosome 13q21.1-qter deletions, we applied 244k Agilent oligonucleotide-based array-CGH to determine the exact breakpoints in 14 patients with partial deletions of this region. Subsequently, we linked the genotype to the patient's phenotype. Using this approach, we were able to refine the smallest deletion region linked to short stature (13q31.3: 89.5-91.6 Mb), microcephaly (13q33.3-q34), cortical development malformations (13q33.1-qter), Dandy-Walker malformation (DWM) (13q32.2-q33.1), corpus callosum agenesis (CCA) (13q32.3-q33.1), meningocele/encephalocele (13q31.3-qter), DWM, CCA, and neural tube defects (NTDs) taken together (13q32.3-q33.1), ano-/microphthalmia (13q31.3-13qter), cleft lip/palate (13q31.3-13q33.1), lung hypoplasia (13q31.3-13q33.1), and thumb a-/hypoplasia (13q31.3-q33.1 and 13q33.3-q34). Based on observations of this study and previous reports we suggest a new entity, "distal limb anomalies association," linked to 13q31.3q33.1 segment. Most of the individuals with deletion of any part of 13q21qter showed surprisingly similar facial dysmorphic features, and thus, a "13q deletion facial appearance" was suggested. Prominent nasal columella was mapped between 13q31.3 and 13q33.3, and micrognathia between 13q21.33 and 13q31.1. The degree of mental delay did not display a particular phenotype-genotype correlation on chromosome 13. In contrast to previous reports of carriers of 13q32 band deletions as the most seriously affected patients, we present two such individuals with long-term survival, 28 and 2.5 years.

DELETION MAPPING OF CRITICAL REGION FOR HYPOSPADIAS, PENOSCROTAL TRANSPOSITION AND IMPERFORATE ANUS ON HUMAN CHROMOSOME 13

BACKGROUND: The 13q-deletion syndrome causes human congenital birth defects due to the loss of regions of one long arm of human chromosome 13. A distal critical region for severe genitourinary and anorectal birth defects in the region of 13q32.2-34 has been suggested; we sought to narrow this critical region. METHODS: From patients with karyotypes revealing haploinsufficiency for distal chromosome 13q and their parents, peripheral blood was obtained and lymphocytes were immortalized for DNA isolation. Genetic and molecular cytogenetic methods were used to map deletions. Patient and parental samples were genotyped with a panel of 20 microsatellite markers spanning 13q31.3 qter and deletions identified by loss of heterozygosity. Deletions were also mapped using a panel of 35 BAC clones from the same region as probes for fluorescence in-situ hybridization on patient lymphoblastoid metaphase preparations. The data were synthesized and a deletion map defining the critical region was generated. RESULTS: Eight patients with known deletions around 13q32qter and their parents were analyzed, and categorized into three groups: three patients with anorectal and genitourinary anomalies (hypospadias, penoscrotal transposition), four male patients without anorectal and genitourinary anomalies, and one XY patient with ambiguous genitalia without anorectal anomalies. We mapped the critical region for anorectal and genitourinary anomalies to a approximately 9.5-Mb interval of 13q33.3-q34 delineated by markers D13S280-D13S285; this spans approximately 8% of the chromosome and contains 20 annotated genes CONCLUSION: The critical region of chromosome 13q mediating genitourinary/anorectal anomalies has been mapped, and will be narrowed by additional patients and further mapping. Identification of the gene(s) mediating these syndromic genitourinary defects should further our knowledge of molecular mediators of non-syndromic hypospadias, penoscrotal transposition and anorectal malformations.

Prenatal diagnosis of the 13q-syndrome through three-dimensional ultrasonography: a case report

CONTEXT

The deletion of the short arm of the chromosome 13, also known as 13q syndrome, is an extremely rare chromosomal disorder. Clinical manifestations include retinoblastoma, brain anomalies, mental and growth retardation, as well as renal, cardiac, gastrointestinal, facial, lip and digital defects. Antenatal diagnosis is suspected when the presence of anomalies is detected and it is confirmed through chromosome analysis.

CASE REPORT

We reported a case of the 13q syndrome which was diagnosed in the 23rd week of gestation in a fetus with holoprosencephaly and we discussed the two and three-dimensional ultrasonography main findings. This is the first case reported in MEDLINE involving the use of three-dimensional ultrasonography in the structural anomalies evaluation of this syndrome.

Prenatal diagnosis of 13q-syndrome in a fetus with Dandy-Walker malformation

BACKGROUND

Partial deletion of the long arm of the chromosome 13 is a rare chromosomal aberration and may present with microcephaly, colobomata, microphthalmia, distal limb and digital anomalies, cardiac defects, brain and urogenital malformations, anal atresia and growth restriction.

CASE

We report such a case in 25th week of gestation referred for sonographic examination which revealed growth restriction, microcephaly, Dandy-Walker malformation, right microphthalmia, micrognathia, marked nuchal edema, four fingers-oligodactyly in feet and in hands with thumb aplasia and ambiguous genitalia. Chromosome analysis identified chromosome 13q deletion [46 XY del (13) (13q31.2/q32.1 --> qter)]. Postmortem examination confirmed prenatal findings and showed aniridia, low-set ears, cryptorchidism, and anal atresia.

CONCLUSION

Detection of Dandy-Walker malformation, microphthalmia, oligodactyly with thumb aplasia and growth restriction during prenatal ultrasonography should be a reminder of deletion of chromosome 13q and warrant cytogenetic analysis.

Holoprosencephaly and limb reduction defects: a consideration of Steinfeld syndrome and related conditions

Individuals with holoprosencephaly (HPE) and limb reduction defects have been ascribed historically to a variety of syndromes with overlapping phenotypic features. As such, these patients are challenges for clinicians and researchers alike. In an effort to better understand this association, we reviewed our autopsy records and identified five cases of HPE with reduction defects of the limbs and other anomalies. One case appears to be the third reported instance of Steinfeld syndrome, while others represent microgastria-limb reduction sequence, VATER/VACTERL association, and an additional unique condition characterized by HPE, rhombencephalosynapsis, absent left radius, first metacarpal, and thumb, and congenital heart disease. The phenotypic heterogeneity inherent in these patients continues to complicate diagnosis, which will hopefully be simplified by continuing delineation at morphologic and especially genetic levels.

Identification and characterisation of constitutional chromosome abnormalities using arrays of bacterial artificial chromosomes

Constitutional chromosome deletions and duplications frequently predispose to the development of a wide variety of cancers. We have developed a microarray of 6000 bacterial artificial chromosomes for array-based comparative genomic hybridisation, which provides an average resolution of 750 kb across the human genome. Using these arrays, subtle gains and losses of chromosome regions can be detected in constitutional cells, following a single overnight hybridisation. In this report, we demonstrate the efficiency of this procedure in identifying constitutional deletions and duplications associated with predisposition to retinoblastoma, Wilms tumour and Beckwith–Wiedemann syndrome.

High-Resolution Analysis of Genetic Events in Cancer Cells Using Bacterial Artificial Chromosome Arrays and Comparative Genome Hybridization

Chromosome analysis of cancer cells has been one of the primary means of identifying key genetic events in the development of cancer. The relatively low resolution of metaphase chromosomes, however, only allows characterization of major genetic events that are defined at the megabase level. The development of the human genome-wide bacterial artificial chromosome (BAC) libraries that were used as templates for the human genome project made it possible to design microarrays containing these BACs that can theoretically span the genome uninterrupted. Competitive hybridization to these arrays using tumor and normal DNA samples reveals numerical chromosome abnormalities (deletions and amplifications) that can be accurately defined depending on the density of the arrays. At present, we are using arrays with 6,000 BACs, which provide an average resolution of less than 700 kb. Analysis of tumor DNA samples using these arrays reveals small deletions and amplifications that were not detectable by chromosome analysis and provides a global view of these genetic changes in a single hybridization experiment in 24 hours. The extent of the genetic changes can then be determined precisely and the gene content of the affected regions established. These arrays have widespread application to the analysis of cancer patients and their tumors and can detect constitutional abnormalities as well. The availability of these high-density arrays now provides the opportunity to classify tumors based on their genetic fingerprints, which will assist in staging, diagnosis, and even prediction of response to therapy. Importantly, subtle genetic changes that occur consistently in tumor cell types may eventually be used to stratify patients for clinical trials and to predict their response to custom therapies.

Brains and faces in holoprosencephaly: pre- and postnatal description of 30 cases

OBJECTIVE

To investigate the prenatal appearance of the holoprosencephaly spectrum.

METHODS

A database of 1750 fetuses with congenital anomalies identified by ultrasound was prospectively collected from 1987 to 2000. Among them, 30 cases (1.7%) with holoprosencephaly were prenatally identified and described.

RESULTS

The prevalence of holoprosencephaly in the Health Region of the National Center for Fetal Medicine in Norway was 1.26 : 10 000; the sex distribution (male : female) was 1.4 : 1. Holoprosencephaly was found in one dichorionic twin pregnancy and one pair of conjoined twins. Among the 30 cases of holoprosencephaly, 18 were alobar, five were semilobar, two were lobar, two were lobar variants, and three were anencephalic. The facial features varied considerably. Sixty-seven per cent (20/30) had associated structural anomalies that were not related to the cerebral and facial holoprosencephaly condition. Thirty-seven per cent (11/30) had detectable chromosome aberrations and 23% (7/30) had nonchromosomal syndromal origin. The size or shape of the head was abnormal in 83% (25/30) of holoprosencephaly cases.

CONCLUSION

This study indicates that holoprosencephaly represents a heterogeneous entity with different etiologies and clinical appearances. The fact that holoprosencephaly features are found associated with particular conditions such as fronto-nasal dysplasia (2/30; 6.7%), agnathia-otocephaly (3/30; 10%), and anencephaly (3/30; 10%), suggests that these may be underreported conditions in other large holoprosencephaly series.