Tetrasomy 9p mosaicism associated with a normal phenotype

Isochromosome (tetrasomy) 9p is a rare chromosomal aberration characterized by phenotypic abnormalities ranging from mild developmental delay to multiple anomalies including intrauterine growth retardation, cerebral ventriculomegaly, dysmorphic facial features, cleft lip or palate, abnormal genitalia and renal anomalies. We present a patient with isochromosome (tetrasomy) 9p mosaicism who is a healthy normal adult male with oligospermia who has fathered two normal children. This chromosomal abnormality may be tissue specific, with a higher detection rate in cultured lymphocytes compared with fibroblasts. Therefore, there is an increased chance of missing the abnormality prenatally by amniocentesis or chorionic villus sampling. We are aware of only one other patient in the literature with a normal phenotype associated with mosaicism for this chromosomal abnormality.     

Rhombencephalosynapsis in a severely polymalformed fetus with non-mosaic tetrasomy 9p, in intracytoplasmic-sperm-injection pregnancy

CASE REPORT: A fetus with rhombencephalosynapsis and prenatally diagnosed tetrasomy 9p is reported. Chromosomal analysis from amniocyte culture revealed non-mosaic supernumerary chromosome identified as isochromosome 9p (9p24-->q13::q13-->p24). Ultrasound scan revealed intrauterine growth retardation, renal anomalies, cardiac anomalies, ventriculomegaly, and agenesis of cerebellar vermis with fusion of the cerebellar hemispheres. CONCLUSION: Although most cases of cerebellar vermis agenesis in tetrasomy 9p are described with cystic malformation such as Dandy-Walker anomaly, our case indicates that this chromosomal disorder should be taken into account in fetuses with the development of cystic and non-cystic malformations of cerebellar vermis and posterior fossa.     

Prenatal diagnosis of tetrasomy 9p in a 19-week-old fetus with Dandy-Walker malformation: a case report

OBJECTIVE: The presentation of sonographic and perinatal findings of tetrasomy 9p. METHODS AND RESULTS: Chorionic villus sampling and amniocentesis were performed at 19 weeks of gestation because of the sonographic findings of Dandy-Walker malformation with bilateral ventriculomegaly. Cytogenetic analysis showed 47,XX,+i psu dic(9)(pter->q12::q12>-pter). The pregnancy was terminated at 20 weeks of gestation at the request of the parents. At post-mortem examination, the presumed hypoplasia of the vermis could not be confirmed for technical reasons. No other pathological findings were seen. CONCLUSION: From our experience and from the literature, we conclude that Dandy-Walker malformation is an important finding in tetrasomy 9p. Chromosomal studies should be carried out in fetuses with sonographically detected Dandy-Walker malformation, even in the absence of other abnormalities.     

Mosaic tetrasomy 9p at amniocentesis: Prenatal diagnosis,molecular cytogenetic characterization,and literature review

ObjectiveThis study was aimed at prenatal diagnosis of mosaic tetrasomy 9p and reviewing the literature.Materials and methodsA 37-year-old woman underwent amniocentesis at 20 weeks' gestation because of advanced maternal age and fetal ascites. Cytogenetic analysis of cultured amniocytes revealed 21.4% (6/28 colonies) mosaicism for a supernumerary i(9p). Repeat amniocentesis was performed at 23 weeks' gestation. Array comparative genomic hybridization, interphase fluorescence in situ hybridization, and quantitative fluorescent polymerase chain reaction were applied to uncultured amniocytes, and conventional cytogenetic analysis was applied to cultured amniocytes.ResultsArray comparative genomic hybridization analysis of uncultured amniocytes detected a genomic gain at 9p24.3–9q21.11. Interphase fluorescence in situ hybridization analysis of uncultured amniocytes using a 9p24.3-specific probe RP11-31F19 (spectrum red) showed four red signals in 47.1% (49/104 cells) in uncultured amniocytes. Cytogenetic analysis of cultured amniocytes revealed a karyotype of 47,XX, +idic(9)(pter→q21.11::q21.11→pter)[4]/46,XX[20] and 16.7% (4/24 colonies) mosaicism for tetrasomy 9p. Quantitative fluorescent polymerase chain reaction confirmed a maternal origin of tetrasomy 9p. The pregnancy was terminated, and a malformed fetus was delivered with hydrops fetalis and facial dysmorphism. The fetal blood cells had 32.5% (13/40 cells) mosaicism for tetrasomy 9p.ConclusionMosaic tetrasomy 9p at amniocentesis can be associated with fetal ascites and hydrops fetalis. The mosaic level of tetrasomy 9p may decrease after long-term tissue culture in amniocytes in case of mosaic tetrasomy 9p.     

Mosaic tetrasomy 9p at amniocentesis in a pregnancy associated with a favorable fetal outcome,perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy in various tissues

ObjectiveWe present mosaic tetrasomy 9p at amniocentesis in a pregnancy associated with a favorable fetal outcome, perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy in various tissue.Case reportA 33-year-old primigravid woman underwent elective amniocentesis at 18 weeks of gestation because of anxiety, and the karyotype of cultured amniocytes was 47,XX,+i (9) (p10)[20]/46,XX [55]. Cordocentesis was performed at 20 weeks of gestation, and the karyotype of cord blood was 47,XX,+i (9) (p10)[7]/46,XX [15]. She was referred for genetic counseling at 23 weeks of gestation, and repeat amniocentesis revealed a karyotype of 47,XX,+i (9) (p10)[1]/46,XX [16] with seven cells in one colony having tetrasomy 9p in cultured amniocytes, and in uncultured amniocytes, quantitative fluorescence polymerase chain reaction (QF-PCR) analysis excluded uniparental disomy (UPD) 9 and determined paternal origin of the extra i (9p), array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr 9p24.3p13.1 × 3.0 consistent with 50% mosaicism for tetrasomy 9p, and interphase fluorescence in situ hybridization (FISH) on uncultured amniocytes showed 22.6% (12/53 cells) mosaicism for tetrasomy 9p. A third amniocentesis at 27 weeks of gestation revealed a karyotype of 46, XX (10/10 colonies) in cultured amniocytes, and interphase FISH analysis on uncultured amniocytes revealed 20% (20/100 cells) mosaicism for tetrasomy 9p. The parental karyotypes and prenatal ultrasound were normal. At 39 weeks of gestation, a phenotypically normal 3388-g female baby was delivered. The karyotypes of cord blood, umbilical cord and placenta were 47,XX,+idic (9) (q12)[19]/46,XX [21] or 47,XX,+idic (9) (pter→q12:q12→pter)[19]/46,XX [21], 47,XX,+idic (9) (q12)[1]/46,XX [39] and 47,XX,+idic (9) (q12)[4]/46,XX [36], respectively. When follow-up at age two months, the neonate was phenotypically normal, the peripheral blood had a karyotype of 47,XX,+idic (9) (q12)[18]/46,XX [22], and interphase FISH analysis on 100 buccal mucosal cells revealed 1% (1/100 cells) mosaicism for tetrasomy 9p. When follow-up at age seven months, the neonate was phenotypically normal, and the peripheral blood had a karyotype of 47,XX,+idic(9)(q12)[14]/46,XX[26].ConclusionMosaic tetrasomy 9p at amniocentesis can be a transient and benign condition, and can be associated with a favorable fetal outcome and perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy in various tissue.     

Prenatal diagnosis of tetrasomy 9p with Dandy-Walker malformation

OBJECTIVES: To add to the knowledge of chromosomal abnormalities associated with Dandy-Walker malformation. METHODS: Molecular cytogenetic analyses of a chorionic villus sampling and of an amniocentesis of a fetus with Dandy-Walker malformation and abnormal somatic development. RESULTS: All cells examined showed a 47, XY, +idic(9p)(pter-->q12::q12-->pter) de novo karyotype. This report describes the fourth case of a tetrasomy 9p associated with Dandy-Walker malformation. CONCLUSIONS: This case, together with the three previously reported cases of an association with a tetrasomy 9p, indicate that this chromosomal aberration should be looked for when Dandy-Walker malformation is detected via prenatal ultrasonography.     

Multiple congenital anomalies in association with supernumerary chromosome 47 inherited from a maternal balanced translocation.

Tertiary trisomy is uncommon and may arise only when one of the derivatives is small and, in the abnormal individual with karyotype 47, exists as a supernumerary derivative chromosome (+der). We describe a case of 47, XY, +der(9)t(5;9) (q33.1;q13)mat. The patient (a 1-day-old male) presented with multiple congenital anomalies including microcephaly, wide fontanelles and sutures, microphthalmia, deep-set eyes, short palpebral fissures, bulbous nose, wide nasal bridge, high arched palate, low-set and posteriorly rotated ears, micrognathia, short neck, ptosis, patient ductus arteriosus, hypoplastic external genitalia, cryptorchidism, inguinal hernia, flexion contractures of joints, short stature, clenched hands, rocker-bottom feet, simian crease, distal mottling of the skin, nail hypoplasia, hypoplasia of bones and hydrocephalus. The supernumerary derivative chromosome resulted from a meiotic recombination of a maternal balanced translocation, t(5;9) (q33.1;q13), suggesting that 3:1 disjunction in the oocyte occurred.     

Partial tetrasomy 18 mosaicism: Pre and postnatal diagnosis of a unique pattern

ObjectiveTo present prenatal diagnosis and cytogenetic characterization of a unique pattern of partial tetrasomy 18 mosaicism.Case reportA 34-year-old woman underwent amniocentesis at 25 weeks of gestation due to anomalies detected in obstetric ultrasound. It revealed a de novo supernumerary partial isochromosome 18 in 11 of 37 metaphases of cultured amniocytes. The karyotype was 47,XX,+idic(18) (q12.3)[11]/46,XX[26]. Elective cesarean section was performed at 33 weeks of gestational age due to anhydramnios. A female symmetric small for gestational age baby with dysmorphic features and an Apgar score of 9/10/10 was born. She had a good clinical outcome during hospitalization. Postnatal peripheral blood karyotype was normal. Interphase fluorescence in situ hybridization in a sample of the oral mucosa confirmed the prenatal diagnosis. At three months of corrected age she had a normal psychomotor development.ConclusionTo the best of our knowledge, this is the first reported case of mosaic partial tetrasomy 18 including segments of the long arm. This newborn's relatively mild phenotype highlights the challenges of prenatal genetic counselling in mosaic cases with fetal anomalies.     

Prenatal diagnosis of Pallister-Killian syndrome: resolution of cytogenetic ambiguity by use of fluorescent in situ hybridization.

We report a case of Pallister-Killian syndrome initially diagnosed prenatally as tetrasomy 21. A 33-year-old primiparous woman was noted at 24 weeks' gestation to have moderate polyhydramnios. Ultrasonography showed diminished fetal stomach filling, hydronephrosis, and prominence of the cisterna magna. Cytogenetic analysis of cultured amniocytes was initially interpreted as mosaic tetrasomy 21: 46,XX/47,XX,+i(21q). The patient was then referred to our centre for genetic counselling. At 34 weeks' gestation, a dysmorphic infant was delivered and died within 30 min. Physical features were consistent with the Pallister-Killian syndrome. Renal, gastrointestinal, and central nervous system anomalies were found at post-mortem examination. Analysis of peripheral lymphocytes revealed 5 per cent of cells with a marker chromosome, while 92 per cent of cultured fibroblasts had this same marker. Fluorescent in situ hybridization (FISH) using an alpha-satellite probe for chromosomes 13 and 21 failed to hybridize to the marker, while a chromosome 12 centromeric probe unequivocally identified it as an i(12p). Use of FISH can provide rapid, specific prenatal diagnosis of ambiguous marker chromosomes and improve prenatal counselling.     

Survival up to age 10 years in a patient with partial duplication 6q: case report and review of the literature

Partial duplication of chromosome 6q has been recognized as a distinct dysmorphic syndrome with severe psychomotor and growth retardation, typical craniofacial features including microcephaly and microstomia, neck webbing, congenital contractures, and variable internal malformations. Most patients have died in the first year of life. We describe the clinical features and disease course in a boy with a duplication of 6q23.3-qter who lived up to the age of 10 years and discuss similarities with other patients.     

Bethlem myopathy in a Taiwanese family.

We report three cases of Bethlem myopathy from three consecutive generations of a Taiwanese family, including one woman aged 70, one man aged 40, and a boy aged 8. The clinical features of the patients included autosomal dominant inheritance, childhood or adolescent onset, mainly proximal and extensor involvement, early diffuse joint contractures, and absence of cardiac involvement. These features fulfilled the diagnostic criteria for Bethlem myopathy. Though the clinical course of the disease was once thought to be benign, our female patient became wheelchair-bound at the age of 53. This suggests that the disease process in Bethlem myopathy is slow but ongoing.     

A case of 3q29 microdeletion with novel features and a review of cytogenetically visible terminal 3q deletions

A further case of 3q29 deletion, in a 13-year-old boy, is described and compared with previous reports. Our case shares a number of dysmorphic and neurodevelopmental features with previously reported individuals with 3q29 microdeletion and is the second reported case with deceleration in head growth--which may be a useful diagnostic clue. Novel features, which may expand the phenotype, include nasal voice, six lumbar vertebrae, lower limb contractures and cerebral sigmoid venous thrombosis. Additionally, cases with cytogenetically visible terminal 3q deletions are reviewed.     

Prenatal diagnosis of a case of tetrasomy 9p

A male fetus with tetrasomy 9p [47,XY, + i(9p)] is presented. The cytogenetic interpretation of the marker chromosome was confirmed by assessing the activity of the enzyme galactose I-phosphate uridyl transferase. The clinical findings of the case show features in common with previously reported cases.     

Retrospective diagnosis of Pallister-Killian syndrome by CGH array

OBJECTIVE AND METHODS: We report a girl presenting with a polymalformation syndrome. Despite a normal karyotype on peripheral lymphocytes and the unavailability of cultured fibroblasts, a tetrasomy 12p was identified on pulmonary DNA extracted from a postmortem biopsy, by use of comparative genomic hybridization (CGH) and confirmed by CGH array. The clinical picture of our patient was consistent, but not specific of the diagnosis of Pallister-Killian syndrome. She presented with the association of antenatal polyhydramnios, craniofacial dysmorphic features, skeletal abnormalities, and a congenital cardiopathy. CONCLUSION: We discuss the usefulness of CGH and CGH array in prenatal and constitutional cytogenetics.     

Relatively mild phenotype in a patient with interstitial 6q24.3-q25.2 deletion

We report a patient with a de-novo interstitial deletion of chromosome 6 with breakpoints at q24.3-q25.2. The patient presented with intra-abdominal testes, mild dysmorphic features, feeding difficulties in the first 3 years of life and normal development with no learning difficulties. To our knowledge this is the first report of a 6q interstitial deletion with these particular breakpoints. This is also the first patient with an interstitial 6q deletion and normal intellectual development. Cryptorchidism seems to be a recurrent finding in males with 6q deletions involving similar breakpoints.     

Unbalanced cryptic translocation der(14)t(9;14)(q34.3;q32.33) identified by subtelomeric FISH

We investigated a girl with dysmorphic features and moderate developmental delay by subtelomeric FISH (fluorescence in-situ hybridization). We found an unbalanced cryptic translocation, t(9;14)(q34.3;q32.33), resulting in a subtelomeric deletion of 14q and duplication of 9q deriving from a balanced translocation in the mother. A review of the literature suggests that the phenotype of our case is related to the 14 qter deletion, without signs of concomitant partial trisomy 9. The case reinforces the value of subtelomeric screening for genetic counselling.     

Small inherited terminal duplication of 7q with hydrocephalus,cleft palate,joint contractures,and severe hypotonia

We report a 14-month-old girl with submucous cleft palate, resolving mild hydrocephalus, severe hypotonia and joint contractures. The finding of extreme hydrocephalus, cleft palate and club feet in a fetus of the mother's previous pregnancy suggested an inherited defect. Chromosome analysis and FISH studies in the proband revealed an abnormal homolog 13 resulting in a duplication of distal chromosome 7q, 7q35-qter, and a very small associated deletion of distal chromosome 13q, 13q34-qter. The mother showed the balanced translocation. Similar clinical signs have been described with larger distal 7q duplications. Our findings suggest that 7q35-qter, and possibly the gene for sonic hedgehog (SHH) on 7q36, is the critical region for the typical facial features and the profound hypotonia observed in the 'trisomy of distal 7q' syndrome.     

Chromosomal abnormalities associated with omphalocele

Fetuses with omphalocele have an increased risk for chromosomal abnormalities. The risk varies with maternal age, gestational age at diagnosis, association with umbilical cord cysts, complexity of associated anomalies, and the contents of omphalocele. There is considerable evidence that genetics contributes to the etiology of omphalocele. This article provides an overview of chromosomal abnormalities associated with omphalocele and a comprehensive review of associated full aneuploidy such as trisomy 18, trisomy 13, triploidy, trisomy 21, 45,X, 47,XXY, and 47,XXX, partial aneuploidy such as dup (3q), dup (11p), inv (11), dup (1q), del (1q), dup (4q), dup (5p), dup (6q), del (9p), dup (15q), dup(17q), Pallister-Killian syndrome with mosaic tetrasomy 12p and Miller-Dieker lissencephaly syndrome with deletion of 17p13.3, and uniparental disomy (UPD) such as UPD 11 and UPD 14. Omphalocele is a prominent marker for chromosomal abnormalities. Perinatal identification of omphalocele should alert chromosomal abnormalities and familial unbalanced translocations, and prompt thorough cytogenetic investigations and genetic counseling.     

Clinical, cytogenetic, and molecular analyses of prenatally diagnosed mosaic tetrasomy for distal chromosome 15q and review of the literature

OBJECTIVES: To present prenatally detected mosaic tetrasomy for distal chromosome 15q and a review of the literature. CLINICAL SUBJECT AND METHODS: Amniocentesis was performed at 17 weeks' gestation because of advanced maternal age. Cytogenetic analysis revealed mosaicism for an analphoid supernumerary marker chromosome (SMC). The parental karyotypes were normal. Fluorescence in situ hybridization (FISH) and polymorphic DNA marker analysis were applied to study the origin of the SMC. Level II ultrasound revealed gastric dilation. The pregnancy was terminated, and a malformed fetus was delivered with characteristic dysmorphism. Multiple samplings of fetal and extraembryonic tissues were performed to investigate the mosaicism. RESULTS: Initial amniocentesis revealed mos 47,XY,+ mar[20]/46,XY[1], and repeat amniocentesis revealed 47,XY,+ mar[28]/46,XY[8]. FISH and polymorphic DNA marker analysis determined an origin from the distal 15q and an inverted duplication of 15q25.3 --> qter for the SMC. Karyotype of the fetus was designated as 47,XY,+ ace i(15) (qter --> q25.3::q25.3 --> qter)/46,XY de novo. The levels of tetrasomy for distal 15q were 28/40 in cord blood, 13/40 in liver, 14/40 in lungs, 27/40 in skin, 0/40 in placenta, and 40/40 in umbilical cord. The placenta showed an equal biparental inheritance (1:1). The umbilical cord inherited one copy of a paternal allele and three copies of a maternal allele (1:3) at distal 15q. Diallelic patterns with dosage ratios (paternal allele: maternal allele) of 1:2.5 in amniocytes, 1:2.3 in amnion, 1:2.2 in cord blood, 1:2.1 in skin, 1:1.4 in liver, and 1:1.4 in lungs. A maternal origin of the mosaic SMC(15) was determined. CONCLUSIONS: A diagnosis of mosaic analphoid SMCs in amniocytes should alert mosaic mirror-image duplication of euchromatin from some distal chromosomal segment such as distal 15q or distal 13q, and a risk for fetal abnormalities. Fetuses with mosaic tetrasomy for distal 15q may be associated with fetoplacental chromosomal discrepancy. Postnatal samplings of umbilical cord, placenta and amniotic membrane may provide additional clues to the cytogenetic discrepancy between fetal and extraembryonic tissues in prenatally detected mosaic analphoid SMCs.     

A patient with a de novo t (6;9) and an interstitial duplication of (9)(q21.2q22.1).

We report on a 4-year-old child with psychomotor retardation, general hypotonia and only mild dysmorphic features. Her chromosome constitution was 46,XX, t (6;9) (q27;q22.1), dup (9) (q21.2q22.1). This de novo interstitial duplication was confirmed using fluorescence in situ hybridisation (FISH) with band-specific probes. This is the second report of a patient with an interstitial duplication of this region of the long arm of chromosome 9. It is concluded that in a child with an abnormal phenotype and a de novo (apparently) balanced translocation, the possibility of a small duplication or deletion should be considered.