Maternal balanced translocation (4;21) leading to an offspring with partial duplication of 4q and 21q without phenotypic manifestations of Down syndrome

We describe an 8-years old female with supernumerary chromosome der(21)t(4;21)(q25;q22) resulting in partial trisomy 4q25-qter and partial trisomy 21(pter-q22). The extra material was originated from a reciprocal balanced translocation carrier mother (4q;21q). Karyotyping was confirmed by FISH using whole chromosome painting probes for 4 and 21q and using 21q22.13-q22.2 specific probe to rule out trisomy of Down syndrome critical region. Phenotypic and cytogenetic findings were compared with previously published cases of partial trisomy 4q and 21q. Our patient had the major criteria of distal trisomy 4q namely severe psychomotor retardation, growth retardation, microcephaly, hearing impairment, specific facies (broad nasal root, hypertelorism, ptosis, narrow palpebral fissures, long eye lashes, long philtrum, carp like mouth and malformed ears) and thumbs and minor feet anomalies. In spite of detection of most of the 3 copies of chromosome 21, specific features of Down syndrome (DS) were lacked in this patient, except for notable bilateral symmetrical calcification of basal ganglia. This report represents further delineation of the phenotype-genotype correlation of trisomy 4q syndrome. It also supports that DS phenotype is closely linked to 21q22. Nevertheless, presence of basal ganglia calcification in this patient may point out to a more proximal region contributing in its development in DS, or that genes outside the critical region may influence or control manifestations of DS features.     

Trisomy 21q223 and Down's phenotype correlation evidenced by in situ hybridization

Summary Two cases of trisomy 21q223 with the Down's phenotype were analysed by in situ hybridization with specific probes previously located in the sub-bands 21q221 (SOD-A) and 21q223 (BCEI and COL6A). These studies give evidence that the clinical picture of Down's syndrome is at least to a great extent correlated with trisomy for the 21q223 band.     

Partial trisomy 9q syndrome with a de novo tandem duplication of 9q22.2-q31.1

A female with a de novo tandem duplication of 9q22.2-q31.1 is presented. Molecular delineation of the breakpoints was made by microarray CGH and fluorescent in situ hybridisation. Involvement of 9q22.2-q31.1 seems to be sufficient to produce the characteristic phenotype of partial trisomy 9q syndrome. A discussion on the recognizable clinical features of the condition is presented.     

Partial trisomy 21 with 45 chromosomes due to translocation of two chromosomes 21 onto a chromosome 14 : 45,XX-14,-21,+t(14q21q21q) (author's transl)

A patient with the phenotype of trisomy 21 and increased activity of superoxide dismutase A is reported with partial trisomy for the distal portion of 21q. The exceptional feature in this case is a 45-chromosome karyotype due to the translocation of two chromosomes 21 onto the distal end of 14q.     

Isochromosome not translocation in trisomy 21q21q

Summary After primary trisomy, de novo 21q21q trisomy is the most frequent chromosomal aberration responsible for Down syndrome. This rearrangement is more commonly referred to as a Robertsonian translocation or centric fusion product than as an isochromosome, e.g., t(21q;21q) instead of i(21q); however, in practice, it has not so far proved possible to distinguish between these alternatives. The aim of this work was to establish which of the two alternatives is acceptable.     

Trisomy 21 by mirror duplication 46,XX,psu dic(21)ter rea (21q21q) (author's transl)

"Mirror image" duplication of chromosome 21 -- 46,XX,pter dic(21)ter rea(21q21q) -- was observed in a patient with the complete phenotype of trisomy 21 and a ses-sesquialtère de la SOD1.     

Submicroscopic duplication of chromosome 21 and trisomy 21 phenotype (Down syndrome)

Summary A patient with the phenotype of trisomy 21 (Down syndrome) was found to have a normal karyotype in blood lymphocytes and fibroblasts. Assessment of the chromosome 21 markers SOD1, CBS, ETS2, D21S11, and BCEI showed partial trisomy by duplication of a chromosome segment carrying the SOD1, CBS, and ETS2 loci and flanked by the BCEI and D21S11 loci, which are not duplicated. This submicroscopic duplication at the interface of 21q21 and 21q22.1 reduces to about 2000–3000kb the critical segment the trisomy of which is responsible for the phenotype of trisomy 21.     

Partial trisomy of chromosome 21 by maternal translocation t(15;21) (q26.2; q21)]

A balanced reciprocal translocation, t(15;21) (q262;q21) was observed in the mother and maternal grandfather of two patients. The propositus, who received the abnormal chromosome 15 from his mother, is trisomic for the distal part of chromosome 21, and his phenotype is that of classical trisomy 21. His sister, who is trisomic for the proximal part of 21q, is slightly retarded but developmentally normal otherwise.     

A patient with Down syndrome with a de novo derivative chromosome 21

Pure partial trisomy of chromosome 21 is a rare event. The patients with this aberration are very important for setting up precise karyotype-phenotype correlations particularly in Down syndrome phenotype. We present here a patient with Down syndrome with a de novo derivative chromosome 21. Karyotype of the patient was designated as 46,XY,der(21)(p13)dup(21)(q11.2q21.3)dup(21)(q22.2q22.3) with regard to cytogenetic, FISH and array-CGH analyses. Non-continuous monosomic, disomic and trisomic chromosomal segments through the derivative chromosome 21 were detected by array-CGH analysis. STR analyses revealed maternal origin of the de novo derivative chromosome 21. The dual-specificity tyrosine (Y)-phosphorylation regulated kinase 1A (DYRK1A) and Down Syndrome Critical Region 1 (DSCR1) genes that are located in Down syndrome critical region, are supposed to be responsible for most of the clinical findings of Down syndrome. However, our patient is the first patient with Down syndrome whose clinical findings were provided in detail, with a de novo derivative chromosome 21 resulting from multiple chromosome breaks excluding DYRK1A and DSCR1 gene regions.     

Trisomy 16q21»qter

Summary A case of trisomy 16q secondary to a paternal 16/18 translocation is described. A comparison of this case with the few other cases of trisomy 16q described in the literature indicates that trisomy for the long arm of chromosome 16 results in a severely affected phenotype and early death. Conversely, patient with trisomy 16p do not have gross abnormalities. We postulate that the prenatal lethality of full trisomy 16 is mainly due to the trisomy for the long arm.     

Patau's syndrome and 13q21q translocation

Summary This paper reports the case of a one-day-old male child presenting the typical features of Patau's syndrome. The cytogenetic study by means of conventional techniques and GTG and QFQ banding techniques showed that the chromosomal pattern of the propositus was 46,XYq+,-21,+t(13q21q) 15ps+,22ps+, and that the nondisjunction that originated the translocation and trisomy had occurred in the mother.     

9;21相互易位携带者生育多例9p部分三体患者细胞遗传学分析

在河南南阳收集到一个家系4代23人, 其中6人患先天性智力障碍, 具有轻度的面部和小母指畸形等特点, 先证者伴随有癫痫的发生。采用常规的外周血培养染色体G带分析, 发现先证者的核型为：46, XY, der(21) t(9; 21) (9p22.2; 21q22.3)pat, 是部分9p三体。对该家系其他成员的染色体进行分析, 发现所有患者均为部分9p三体, 异常染色体均来自9号与21号染色体平衡易位携带者染色体相互易位的异常分离, 因此这是一个部分9p三体综合征家系。而重复区段发生在9号染色体短臂远端一半区域(9pter→9p21)内, 该区是关键区, 导致智力障碍和面容轻微畸形。     

Partial trisomy 21

Summary Cytogenetic analysis of a 6-year-old girl with moderate mental retardation revealed 46 chromosomes with a tandem translocation (21;21) resulting in a partial trisomy 21. Only the terminal band 21q22 was not in triplicate. G-, Q-, R-, and C-banding techniques and silver nitrate staining of the nucleolus organizer regions (NORs) were used to identify this chromosome fully.The phenotype of the patient was not typical for Down's syndrome, providing additional evidence that trisomy of band 21q22 is pathogenetic for the phenotype of Down's syndrome. This is also a new example in human pathology of a stable dicentric chromosome in which one of the centromeric constrictions appears to be nonfunctional.     

Interchange trisomy 21 by t(1;21)(p22;q22)mat

Interchange trisomy 21 by t(1:21)(p22:q22)mat: Interchange trisomy 21 by t(1;21)(p22;q22)mat was identified in a sporadic patient with Down syndrome. With a 21q22 specific probe, we observed signals on both normal 21 chromosomes and on the der. We reviewed the 23 published reports of families with reciprocal translocations leading to viable offspring with interchange trisomy 21. The breakpoints in chromosome 21 were mainly located in 21q (19/24 instances, including the present report) and in 19/23 cases the other chromosome involved in the translocation was (pairs 1-12). The underlying 3:1 segregation occurred mainly in carrier mothers; only one patient presented a de novo imbalance and in another case the father was the carrier. In addition, there were 4 instances of concurrence with another unbalanced segregation (adjacent-1 or tertiary trisomy) and 3 families with recurrence of interchange trisomy 21. The mean age of 14 female carriers at birth of interchange trisomy 21 offspring (24.8 yr) was lower that the mean (28.3 yr) found in a larger sample of mothers of unbalanced offspring due to 3:1 segregation (mostly tertiary trisomics) and was not increased with respect to the general population average. Overall, these data agree with previous estimates regarding recurrence risk (9-15%) and abortion rate (about 28%) in female carriers ascertained through an interchange trisomic 21 child.     

Partial trisomy and monosomy 21 in an infant with an unusual de novo 21/21 translocation

A 3-month-old boy with a 46,XY,--21,+t(21;21)(pter leads to q22.3::q22.3 leads to q11::p11 leads to pter) karyotype, implicating trisomy for the 21q11 leads to 21q22.2 segment and monosomy for the 21q22.3 sub-band, is described. Most of the clinical features corresponded to Down syndrome ; other signs such as large ears, prominent nasal bridge and retromicrognathia were interpreted as the expression of 21q22.3 monosomy. The abnormal monocentric chromosome had satellites and stalks on both ends as a result of a 21q;21q translocation followed by deletion of one centromere region. Despite similar stalk size and NOR-Ag positiveness a significantly higher association frequency of the centrometric end as compared to the acentric end was found. This observation suggests that the satellite association phenomenon is not exclusively NOR-dependent, but that the centromeric and/or p11 regions of acrocentrics also play an important role.     

Down syndrome due to de novo Robertsonian translocation t(14q;21q): DNA polymorphism analysis suggests that the origin of the extra 21q is maternal.

Down syndrome is rarely due to a de novo Robertsonian translocation t(14q;21q). DNA polymorphisms in eight families with Down syndrome due to de novo t(14q;21q) demonstrated maternal origin of the extra chromosome 21q in all cases. In seven nonmosaic cases the DNA markers showed crossing-over between two maternal chromosomes 21, and in one mosaic case no crossing-over was observed (this case was probably due to an early postzygotic nondisjunction). In the majority of cases (five of six informative families) the proximal marker D21S120 was reduced to homozygosity in the offspring with trisomy 21. The data can be best explained by chromatid translocation in meiosis I and by normal crossover and segregation in meiosis I and meiosis II.     

Two new cases of trisomy 10q21 to 10qter in two sisters due to paternal translocation t(9;10) (q34;q24)]

Two sisters with multiple congenital malformations were shown to be trisomic for 10q24 to 10qter as a consequence of malsegregation of the balanced paternal translocation t(9;10) (q34;q24). Comparison of their phenotype with that of other patients reported in the literature confirms the individuality of the partial 10q trisomy syndrome.     

Trisomy 6q syndrome: a case with a < de novo > 6q23 tandem duplication

In this study, we report the combined use of whole and partial chromosome 6 painting probe and YACS probes to define the unbalanced region of a de novo 6q+ marker chromosome. A male patient with peculiar features of < distal 6q trisomy syndrome > showed a direct duplication of 6q23 region. Comparing the phenotype of this child with the phenotype of other < de novo > partial 6q trisomy, we conclude that band 6q23 has an important role in defining 6q trisomy.     

Trisomy 4q26--4qter by t(4;18)(q26;q23)mat translocation]

Partial trisomy 4q and perhaps monosomy 8qter was observed in a malformed girl, due to malsegregation of a t(4;18)(q26;q23)mat. Her phenotype was in agreement with the partial trisomy 4q syndrome, and she died 5 months after birth.