Two unbalanced segregation products due to a maternal t(7;16)inv(16)

We report a prenatal case of a maternally inherited abnormal chromosome 16, originally interpreted as a pericentric inversion only, but after family studies re-interpreted as a pericentric inversion (16) accompanied by an unbalanced (7;16) translocation. Because of the inversion 16 and an elder son with developmental delay and craniofacial dysmorphic features, in the past karyotyped as 46,XY, the chromosomes 16 of the mother and son were carefully re-examined. Using a whole chromosome 16 paint and sub-telomere probes of 16p and 16q, the karyotype of the mother was shown to be 46,XX,inv(16)(p11.2q23.2).ish t(7;16)(q36;p13.3)inv(16). Subsequently one chromosome 16 of the elder son appeared to be a der(16)t(7;16)(q36;p13.3). This is probably the result of a meiotic crossover between the chromosomes 16 in the mother. The prenatal karyotype was finally interpreted as 46,XY,inv(16)(p11.2q23.2).ish der(16)t(7;16)(q36;p13.3)inv(16). This is the same cytogenetic imbalance as his elder brother: a partial trisomy of chromosome 7 (q36-->qter) and a partial monosomy of chromosome 16 (p13.3-->pter).     

Prenatal diagnosis of de novo isochromosome 4p with an unbalanced t(4;9) translocation in a fetus with congenital anomalies: A case report and literature review

ObjectiveWe present the first case of prenatally diagnosed isochromosome 4p with whole 4q arm translocating to chromosome 9p23 and review the literature.Case ReportA 26-year-old woman underwent amniocentesis at 25 weeks of gestation because of an abnormal ultrasound examination. Routine chromosome analysis on cultured amniocytes showed a karyotype of 46,XX, ?idic(4)(q11),der(9)t(4;9)(q11;p23). Single nucleotide polymorphism (SNP) array analysis on uncultured amniocytes detected two copy number variations (CNVs): arr [GRCh37] 4p16.3p11(68345-49089361) × 3; arr [GRCh37] 9p24.3p23(208454-10039391) × 1. The karyotypes of the parents were normal, indicating that the chromosomal rearrangement was de novo. According to the fetal-parent trios SNP analysis, both the abnormal chromosomes were originated from the father. The pregnancy was terminated at 30 weeks of gestation, and a malformed fetus was delivered with dysmorphic craniofacial, short neck, wide-spaced nipples and rocker-bottom feet.ConclusionThe combined application of traditional cytogenetic technology and molecular diagnosis technology in prenatal diagnosis helps identify genetic components and the origin of isochromosome, which enable clinicians to precisely predict the fetal prognosis and provide accurate genetic counselling and fertility guidance.     

Comprehensive meiotic segregation analysis of a 4-breakpoint t(1;3;6) complex chromosome rearrangement using single sperm array comparative genomic hybridization and FISH

Complex chromosomal rearrangements (CCR) represent rare structural chromosome abnormalities frequently associated with infertility. In this study, meiotic segregation in spermatozoa of an infertile normospermic carrier of a 4-breakpoint t(1;3;6) CCR was analysed. A newly developed array comparative genomic hybridization protocol was used, and all chromosomes in 50 single sperm cells were simultaneously examined. Three-colour FISH was used to analyse chromosome segregation in 1557 other single sperm cells. It was also used to measure an interchromosomal effect; sperm chromatin structure assay was used to measure chromatin integrity. A high-frequency of unbalanced spermatozoa (84%) was observed, mostly arising from the 3:3 symmetrical segregation mode. Array comparative genomic hybridization was used to detect additional aneuploidies in two out of 50 spermatozoa (4%) in chromosomes not involved in the complex chromosome rearrangement. Significantly increased rates of diploidy and XY disomy were found in the CCR carrier compared with the control group (P < 0.001). Defective condensation of sperm chromatin was also found in 22.7% of spermatozoa by sperm chromatin structure assay. The results indicate that the infertility in the man with CCR and normal spermatozoa was caused by a production of chromosomally unbalanced, XY disomic and diploid spermatozoa and spermatozoa with defective chromatin condensation.     

Oculoauriculovertebral spectrum phenotype caused by an unbalanced t(5;8)(p15.31;p23.1) rearrangement

We present two siblings with oculoauriculovertebral spectrum phenotype (Goldenhar syndrome) and an unbalanced translocation t(5;8)(p15.31;p23.1) resulting in monosomy for the region 5p15.31 to 5pter and trisomy for 8p23.2 to 8pter region. The father was a carrier of the balanced rearrangement 46,XY,t(5;8)(p15.31;8p23.1). To our knowledge this is the first report of Goldenhar phenotype in association with an unbalanced (5p;8p) translocation.     

Sacrococcygeal teratoma in a fetus with prenatally diagnosed partial trisomy 10q (10q24.3-->qter) and partial monosomy 17p (p13.3-->pter)

OBJECTIVE: Clinical features of the distal 10q trisomy syndrome consist of mental retardation, facial dysmorphism and renal and cardiac anomalies. The presence of a sacrococcygeal teratoma (SCT) in a fetus with distal 10q trisomy has not been reported yet. METHODS: A 33-year-old, G5, P2 woman with a singleton pregnancy was referred to our clinic at 24 weeks of gestation for further evaluation of a fetal sacral exophytic mass. Detailed fetal sonographic examination together with chromosomal analysis by amniocentesis was performed. RESULTS: The scan revealed a large SCT together with a persistent right umbilical vein, cardiomegaly, bilateral mild hydronephrosis and intrauterine growth retardation. The fetal karyotype showed distal 10q trisomy (10q24.3-->qter) distal monosomy 17 (p13-->pter). The fetus died after a preterm delivery at 28 weeks of gestation. Postnatal examination confirmed the prenatal findings and added the typical facial features of this syndrome, which consisted of prominent forehead, small nose with depressed nasal bridge, micrognathia and bow-shaped mouth. CONCLUSION: This case provides further evidence of a possible association between chromosomal aberrations in SCTs.     

Wolf-Hirschhorn syndrome due to a 3:1 segregation of a maternal balanced t(4;15)(p16.3;q11) translocation

The Wolf-Hirschhorn syndrome (WHS) is characterized by severe pre- and postnatal growth retardation, specific pattern of dysmorphisms, and severe developmental delay. These clinical findings are the result of a deletion within the short arm of chromosome 4. Most cases occur de novo and are of paternal origin. Cases due to a balanced translocation are mostly of maternal origin and the deletion of distal 4p, including the WHS critical region, is often combined with a duplication of the other chromosomal segment involved in the rearrangement. Here, we report on a newborn female infant with WHS and pure tertiary monosomy due to a 3:1 segregation of a balanced maternal 4;15 translocation. In this context, importance of fluorescence in situ hybridization (FISH) with specific probes to determine the exact breakpoints in unbalanced chromosomal rearrangements with breakpoints localized around known microdeletion syndromes is emphasized.     

Prenatal diagnosis of a satellited non-acrocentric chromosome derived from a maternal translocation (10;13)(p13;p12) and review of literature

We identified a familial balanced translocation involving chromosomes 10 and 13 through the finding of a satellited 10p chromosome in a fetus. The phenotype of two unbalanced products of the translocation resulting in pure monosomy 10p13 and trisomy 10p13 is described. This familial case and two of our unreported cases are discussed in the light of other prenatal observations with satellited non-acrocentric chromosomes reported in the literature.     

Prenatal diagnosis of an extra der(4) resulting from a complex maternal chromosome translocation

We report the prenatal diagnosis of an extra der(4) resulting from 4:2 malsegregation of a maternal balanced complex translocation involving chromosomes 4, 10, and 11. The woman was referred for amniocentesis because of recurrent miscarriages. Fluorescence in situ hybridization was performed in order to characterize the complex chromosome rearrangement. Following genetic counselling, the couple decided to terminate the pregnancy.     

Mosaic trisomy (8)(p22 --> pter) in a fetus caused by a supernumerary marker chromosome without alphoid sequences

OBJECTIVE: Our objective was to characterise a marker chromosome in cultured amniocytes of a fetus with a mos 47,XX,+mar[3]/46,XX[14] karyotype. METHODS: The indication for prenatal cytogenetic analysis of cultured amniocytes was advanced maternal age. Classic banding techniques (GTG- and C-banding) were performed. Microdissection combined with reverse painting was used to disclose the exact origin of the marker; the result was confirmed by chromosome painting and FISH with band-specific probes. RESULTS: Analysis of GTG-banded chromosomes showed a small marker chromosome in 3 of the 17 colonies analysed. Subsequently, C-banding showed no alphoid sequences, suggesting the presence of a neocentromere. The parent's karyotypes were normal. After normal ultrasound findings, the parents decided to continue the pregnancy. Chromosome analysis in peripheral blood after birth demonstrated that the marker chromosome was present in 50% of the lymphocytes. Using microFISH, the marker was further characterised and appeared to be derived from chromosome region (8)(p22 --> pter). CONCLUSION: Accurate identification of the marker chromosome was very important for prenatal counselling. Combining the results of GTG- and C-banding analysis with the results of the (micro)FISH, we concluded that the patient's karyotype is: mos 47,XX,+mar.rev ish der(8)(p22 --> pter)[50]/46,XX[50].     

Meiotic segregation and interchromosomal effects in a rare (1:2:10) complex chromosomal rearrangement

Purpose  

Complex chromosomal rearrangements (CCR) are rare rearrangements involving more than two chromosomes and more than two breakpoints. CCR are associated with male infertility as a result of the disruption of spermatogenesis due to complex meiotic configurations and the production of chromosomally abnormal sperm. We examined a carrier of a t(1:2:10) CCR in order to determine the patterns of segregation and any presence of an interchromosomal effect (ICE).     

Prenatal diagnosis of a fetus with unbalanced translocation (4;13)(p16;q32) with overlapping features of Patau and Wolf-Hirschhorn syndromes

Wolf-Hirschhorn syndrome (WHS) and Patau syndrome are two of the most severe conditions resulting from chromosome abnormalities. WHS is caused by a deletion of 4p16, while Patau syndrome is caused by trisomy for some or all regions of chromosome 13. Though the etiologies of these syndromes differ, they share several features including pre- and postnatal growth retardation, microcephaly, cleft lip and palate, and cardiac anomalies. We present here a female fetus with deletion of 4p16 --> pter and duplication of 13q32 --> qter due to unbalanced segregation of t(4;13)(p16;q32) in the father. She displayed overlapping features of both of these syndromes on ultrasound. To the best of our knowledge, this is the first report of a fetus with both partial trisomy 13 and deletion of 4p16, the critical region for WHS.     

Bilateral renal agenesis and fetal ascites in association with partial trisomy 13 and partial trisomy 16 due to a 3:1 segregation of maternal reciprocal translocation t(13;16)(q12.3; p13.2).

A female fetus with bilateral renal agenesis and fetal ascites was found to have partial trisomy 13 (pter-q12.3) and partial trisomy 16 (p13.2-pter), 47,XX,+der(13)t(13;16)(q12.3; p13.2)mat. The chromosomal aberration was due to a 3:1 segregation with tertiary trisomy transmitted from a maternal reciprocal translocation 13;16. Prenatal ultrasound of a 29-year-old, gravida 2, para 0 woman at 22 gestational weeks showed fetal ascites, severe oligohydramnios and non-visualization of fetal urinary bladder and kidneys. The pregnancy was terminated. At delivery, the proband displayed dysmorphic features of hypertelorism, a prominent glabella, epicanthic fold, a stubby nose with a depressed nasal bridge, anteverted nares, thin lips, micrognathia, low-set ears, a short neck and a distended abdomen. Necropsy confirmed bilateral renal agenesis and ascites. A cytogenetic study performed on fibroblasts obtained from the proband's skin revealed an extra supernumerary chromosome. The mother was later found to have a reciprocal translocation. Fluorescence in situ hybridization for a submicroscopic deletion in chromosome 22q11 in the proband was negative. The parents had no urological anomalies. Our observation further extends the clinical spectrum associated with proximal trisomy 13q and distal trisomy 16p. We suggest prenatal cytogenetic analysis in fetuses with urological anomalies, including renal agenesis, to uncover underlying genetic disorders.     

Prenatal diagnosis of a fetus with partial trisomy 7p

We report a prenatal diagnosis of a fetus with partial trisomy 7p. Ultrasonography at 28 weeks of gestation of a 27-year-old multigravid woman revealed a growth-retarded fetus with agenesis of the corpus callosum, enlarged left kidney, single umbilical artery, hypertelorism, depressed nasal bridge, frontal bossing, irregular maxiller alveolar composition, club feet, flexion deformity of the upper extremities and Epstein anomaly. Fetal karyotype was 46,XX,der(9)add(9p24),16qh+. Our results indicated that the fetus had an unbalanced translocation, which resulted in duplication of the proximal segment of 7p. Maternal karyotype was (46,XX,t(7,9)(p15.3,p24),16qh+). Because fetal death occurred at 31 weeks of gestation, induction of labor was performed. An enlarged anterior fontanel and micrognathia were seen during fetal autopsy. Trisomy 7p is related to a well-known clinical picture with a dismal prognosis. Our report showed that the outcome of the affected pregnancy may also be poor. Detection of fetal chromosomal abnormality and parental translocations are essential for counseling of the parents.     

Prenatal diagnosis of a fetus with a cryptic translocation 4p;18p and Wolf-Hirschhorn syndrome (WHS)

Wolf-Hirschhorn Syndrome (WHS) is caused by distal deletion of the short arm of chromosome 4 and is characterized by growth deficiency, mental retardation, a distinctive, 'greek-helmet' facial appearance, microcephaly, ear lobe anomalies, and sacral dimples. We report a family with a balanced chromosomal translocation 4;18(p15.32;p11.21) in the father and an unbalanced translocation resulting in partial monosomy 4 and partial trisomy 18 in one living boy and a prenatally diagnosed male fetus. Both showed abnormalities consistent with WHS and had in addition aplasia of one umbilical artery. Karyotyping of another stillborn fetus revealed a supernumerary derivative chromosome der(18)t(4;18)(p15.32;p11.21) of paternal origin and two normal chromosomes 4. The umbilical cord had three normal vessels. A third stillborn fetus with the same balanced translocation as the father had a single umbilical artery and hygroma colli.     

Prenatal diagnosis of a fetus with distal 10q trisomy.

Distal 10q trisomy is a well-defined but rare syndrome. Most cases are diagnosed in infancy or in childhood and rarely include prenatal findings. We present a case of fetal distal 10q trisomy with abnormal prenatal sonographic findings. A 19-year-old primigravida was referred for genetic counselling at 18 gestational weeks because her husband had a familial history of congenital anomalies. Genetic amniocentesis was thus performed and showed fetal distal 10q trisomy (10q24.1-->qter), 46,XX,der(22)t(10;22)(q24.1;p11.2)pat, resulting from paternal t(10;22) reciprocal translocation. Level II ultrasonograms further demonstrated bilateral hydronephrosis, ventricular septal defect and facial dysmorphism ascertained by three-dimensional ultrasound. The pregnancy was terminated at 22 gestational weeks. Post-mortem autopsy confirmed the sonographic findings. We suggest that abnormal prenatal sonographic findings such as cardio-vascular, renal and facial malformations should alert cytogeneticists to search for subtle chromosomal abnormalities.