Trisomy 20p from maternal translocation and anencephaly. Case report and genetic review

This paper concerns the case of an anencephalus male fetus with partial trisomy 20p product of a maternal translocation 46,XX, t(15;20) (p11.2;p12), ascertained by prenatal diagnosis. A cytogenetic review of previous cases is presented. Several hypotheses are discussed in order to explain the recurrent abortions of the mother and the aetiology of anencephaly in this last pregnancy.     

Trisomy 20p: case report and genetic review

Partial trisomy for the distal part of the short arm of chromosome 20 reported in a girl aged 11/2 years with typical craniofacial dysmorphies and psychomotor retardation. The trisomy resulted from a paternal translocation t(14;20) (q32.3;p11.1). The review of 25 cases of partial trisomy 20p showed that most cases (22 : 25) were due to parental translocations. Predominant involvement of small chromosomes in translocations with chromosome 20 was also detected.     

Severe psychomotor retardation in a boy with a supernumerary derivative chromosome resulting in partial trisomy 21 and partial trisomy 7p

We report on a 12-year-old boy with a supernumerary chromosome der(21)t(7; 21)(p21; q21.3)mat, resulting in a partial trisomy 21 and a partial trisomy 7p. The patient has a severe psychomotor retardation. Although he has most of chromosome 21 in three copies, he does not have a phenotype of Down syndrome (DS). In addition to cytogenetic analysis, molecular analysis confirmed that the "DS critical region" on chromosome 21 (21q22) is not present in three copies, since the breakpoint of the partial trisomy 21 was found to be located distal to the marker locus D21S145 but proximal to D21S226. The patient's severe mental retardation is probably due to the small telomeric 7p trisomy, having the breakpoint between markers D7S507 and D7S488. In comparison with previously published cases of partial trisomy 7p, the phenotype of this patient indicates that there is a region around the distal part of band 7p21 that in three copies might contribute to many of the facial features common to patients with partial trisomy 7p.     

Partial trisomy 20p derived from a t(18;20) translocation

Summary Two sibs show a strikingly concordant syndrome of congenital anomalies and G-banding reveals that each has partial trisomy 20p resulting from a t(18;20) translocation. They resemble other cases of partial trisomy 20p in some respects but also differ in some ways. Their normal sib, mother, and half-aunt are balanced heterozygotes for the t(18;20) translocation. The segregation of the balanced translocation in this family is associated with an extremely poor reproductive record. The segregation pattern closely parallels that of a t(13;20) translocation in a family described by Carrel et al. (1971) and Francke (1972). The similarity of segregation patterns is predictable on the basis of probable pachytene configurations, but the dissimilarity of phenotypes between families is not readily explained.     

De novostructural chromosomal imbalances: molecular cytogenetic characterization of partial trisomies

De novo structural chromosomal imbalances represent a major challenge in modern cytogenetic diagnostics. Based solely on conventional cytogenetic techniques it may be impossible to identify the chromosomal origin of additional chromosomal material. In these cases molecular cytogenetic investigations including multicolor-FISH (M-FISH), spectral karyotyping (SKY), multicolor banding (MCB) and cenM-FISH combined with appropriate single-locus FISH probes are highly suitable for the determination of the chromosomal origin and fine characterization of derivative chromosomes. Here we report on four patients with de novo chromosomal imbalances and distinct chromosomal phenotypes, three of them harboring pure partial trisomies: a mildly affected boy with pure partial trisomy 10q22.2-->q22.3 approximately 23.1 due to an interstitial duplication, a girl with pure trisomy 12p11.21-->pter and atypically moderate phenotype as the consequence of an X;autosome translocation, and a girl with multiple congenital abnormalities and severe developmental delay and a 46,XX,15p+ karyotype hiding a trisomy 17pter-->17q11.1. The fourth patient is a girl with minor phenotypic features and mental retardation with an inverted duplication 18q10-->p11.31 combined with a terminal deletion of 18p32. The clinical pictures are compared with previously described patients with focus on long term outcome.     

Pure partial trisomy 6p due to a familial insertion (16;6)(p12;p21.2p23)

There have only been eight patients with 6p pure trisomy involving different segments: four cases resulted from a translocation or insertion and four were due to an intrachromosomal duplication. We report here the first postnatally ascertained patient with a pure 6p partial trisomy due to an interchromosomal insertion (16;6)(p12;p21.2p23)mat. This rearrangement was confirmed by fluorescent in situ hybridization (FISH) with whole chromosome 6 and 16 painting probes. The clinical findings in the present patient were similar to those observed in previous cases, including craniofacial dysmorphism, minor anomalies, and lack of severe anatomical defects; yet, the unspecificity of many of these features prevented us from delineating the 6p pure trisomy syndrome.     

Partial trisomy 6p due to familial translocation t(6;20)(p21;p13)

Summary Cytogenetic findings in a case of partial trisomy 6p due to a translocation t(6;20)(p21;p13) and eleven balanced translocation heterozygotes are described.The clinical data of the proposita are compared with those of five other published cases. A partial trisomy 6p syndrome is postulated, characterized by: low birth weight, psychomotor retardation, craniofacial abnormalities (such as high prominent forehead, large fontanel, wide sagittal suture, blepharoptosis, low-set and/or malformed ears), congenital heart malformation, small kidneys, and proteinuria. Linkage studies have shown that the breakpoint in chromosome 6 involved in this translocation is close to the HLA gene cluster.     

Familial trisomy 20p five cases and two carriers in three generations a review.

A clinically normal mother of three retarded children has been determined by G-banding to have a balanced translocation 46,XX,t(13;20) (q34;p11.2). The children each have an unbalanced form of the translocation with partial trisomy for 20p. Extensive gene marker studies have been unable to affix any specific gene locus onto the short arm of chromosome 20. The balanced translocation was inherited from the maternal grandfather. Two phenotypically abnormal deceased members of the family are believed to have had the unbalanced trisomy 20p condition. An increases number of spontaneous abortions were possibly due to lethal unbalanced 20p deletions. The moderate to mild mental retardation and somewhate unusual features (round face, prominent cheeks and nose, short mandible) in the three siblings and two other affected relatives suggest that trisomy of the short arm of chromosome 20 may cause a distinguishable clinical syndrome. Vertebral abnormalities and abnormal dermatoglyphics are part of the picture. Clinical and cytogenetic findings of all reported cases are compared.     

Partial trisomy 10q

Summary Five cases from two nonrelated families with partial trisomy 10q due to a reciprocal translocation t(10;17)(q25;p13) and t(10;11)(q24;q23), respectively, are reported. The phenotypic findings are compared with those of 17 previously published cases; the clinical data justify the conclusion that cases with trisomy 10q show a specific syndrome of mental retardation and malformation characterized by psychomotor retardation, growth retardation, hypotonia, high forehead, flat face, fine and arched eyebrows, antimongoloid slant of the eyes, narrow palpebral fissures, hypertelorism, short nose, bowshaped mouth, short neck, (kypho)scoliosis, and in some cases microcephaly.     

Double translocation t(7;12),t(2;6) heterozygosity in one family

Summary Double translocation heterozygosity t(2;6),t(7;12) in three generations of a Dutch family is described: the segregation of a double translocation in more than one generation has not been previously published. The index case was a 16-year-old mentally retarded boy with partial trisomy 12p who showed several dysmorphic features such as high prominent forehead, flat face, flat and short nose bridge, short nose, dysplastic ears, prominent lower lip, and several skeletal abnormalities. Based on the findings in this patient and those in nine other cases, the existence of a specific trisomy 12p syndrome is postulated.     

Clinical and molecular cytogenetic studies in a case with partial trisomy 12p due to a de novo supernumerary ring chromosome

Clinical and molecular cytogenetic studies in a case with partial trisomy 12p due to a de novo supernumerary ring chromosome: We report on a girl with a mosaic karyotype containing a supernumerary ring chromosome. Fluorescence in situ hybridization (FISH) studies showed that this marker chromosome was derived from chromosome 12, resulting in partial trisomy 12p13.1-->12q11. The girl showed developmental delay, cerebral visual impairment, obesity and mild dysmorphic features. Her clinical data at 6 months, 3 years, and 6 years of age were compared with the clinical data on other trisomy 12p patients.     

Partial trisomy of the distal part of 10q: a report of two Egyptian cases

Partial trisomy of the distal third of the long arm of chromosome 10 is a well defined but rare syndrome. Most cases result from an unbalanced translocation. Growth retardation, developmental delay and characteristic dysmorphic features are well described in the syndrome. This report includes 2 Egyptian cases with partial 10q trisomy involving different breakpoints. Cases were subjected to full clinical examination and detailed cytogenetic analysis using conventional and FISH studies. Results showed that the karyotype of case 1 was 46,XX,der(7)t(7;10)(p22;q23).ish(wcp7+;wcpl0+) and the karyotype of case 2 was 46,XX,der(7)t(7;10)(p22;q25).ish(wcp7+;wcp 10+). The chromosomal abnormalities in case 1 resulted from a paternal balanced translocation while case 2 resulted from a maternal balanced translocation involving chromosomes 10 and 7 in both cases. The probands' phenotypes were correlated to the breakpoints and compared to previously reported cases with partial trisomy 10q. Both cases had the well characterized phenotype of the distal trisomy of 10q in the form of mental retardation, microcephaly, characteristic dysmorphic facies and limb anomalies as trisomy in both cases involved the 10q25-->qter region. However, case 1 with 10q23-->qter duplication showed more severe clinical manifestations than case 2 with less extensive 10q25-->qter trisomy. These included severe failure to thrive, cardiac involvement and death from respiratory and heart failure. This study confirmed that unbalanced chromosome regions of the long arm of chromosome 10 play an important role in developmental malformations and that a more severe form is associated with involvement of 10q23. It also emphasizes the importance of increasing public awareness regarding these chromosomal rearrangements and the importance of genetic counseling and prenatal diagnosis to avoid recurrences and associated family stress. This was clearly demonstrated in the second family in this study as the couple refused any follow up or further investigations due to religious beliefs despite their social and educational level.     

Partial trisomy 17q and monosomy 9p due to a familial translocation.

Described is an infant with partial trisomy 17q and monosomy 9p [46,XX,-9,+der(9)t(9;17)(p21;q23)] due to adjacent-1 segregation of a maternal balanced reciprocal translocation. Characteristic clinical features of both partial 17q trisomy and monosomy 9p are present, but the former syndrome is less recognisable in this infant than in previously reported cases due to the concomitant 9p monosomy.     

Pure partial trisomy 5q33-->5q35 resulting from the adjacent-1 segregation of a paternal (5;14)(q33;p12) translocation.

A 14-year-old male was referred for evaluation of mental retardation with short stature and dysmorphic features. His karyotype was 46,XY,der(14)t(5;14)(q33;p12)pat, resulting in a pure partial 5q33-q35 trisomy due to the adjacent-1 segregation of a paternal balanced translocation. Paternal blood karyotype revealed a balanced translocation t(5;14)(q33;p12) retaining Ag-Nors. To date, only two cases of pure partial 5q trisomies spanning this region have been reported. Analysis of these cases and the one we report does not allow the delineation of a specific phenotype.     

A severely mental and motor retarded boy with monosomy 9pter-->p22 trisomy 10q26-->qter due to paternal reciprocal translocation 46,XY,t(9;10)(p23;q26)

We report on a twenty-two months old male patient with hypotonia, mental and motor retardation and trigonocephaly. Standard GTG banding chromosomal analysis (from metaphyses of a periferal blood lymphocyte culture) showed 46,XY, der(9) monosomy 9pter-->p22, trisomy 10q26--> qter karyotype. This unbalanced translocation resulted from the father's t(9,10) (p22;p26) karyotype. Deletions of the terminal part of 9p and partial trisomy of chromosome 10q are rare chromosomal disorders. To our knowledge, this is the first case report in the literature of a deletion of 9pter-->p22.3 and a duplication of 10q26-->qter. We assume that the clinical anomalies are due to der(9) monosomy 9pter-->p22, trisomy 10q-->26qter.     

A new case of partial 14q31.3-qter trisomy due to maternal pericentric inversion

Chromosome 14 is often involved in chromosome rearrangements, although pericentric inversions are rare. Here we report a mother carrying a pericentric inversion of chromosome 14, and her daughter with recombinant chromosome characterized by a partial distal 14q trisomy. Principal clinical findings of the child include facial anomalies, microcephaly, developmental delay, hypotonia and cardiac malformation. Her final karyotype was 46,XX,rec(14)dup(14q)inv(14)(p12q31)mat[20], arr 14q31.3qter(85,427,839–106,356,482)x3. This report brings new data about clinical features of partial 14q trisomy and molecular analysis enables the visualization of genes involved in the segment duplicated.     

Tertiary trisomy of 10p15.pter and 14pter.ql3 due to maternal translocation t(10;14)(p15;q13)

Double partial trisomy resulting from 3:1 segregation of the respective chromosomal segments of the chromosomes involved in a balanced translocation in meiosis is rarely reported in the literature. We present here a first patient with multiple congenital malformations associated with double partial trisomy of 10pter-p15 and 14pter-q13 resulting from 3:1 segregation of maternal balanced translocation t(10;14)(p15;q13). Proximal partial trisomy of chromosome 14 and subterminal trisomy of the short arm of the chromosome 10 are rare. The present case is the first case with double partial trisomy of these segments resulting from 3:1 segregation of a maternal balanced translocation.     

Partial trisomy 10p and familial translocation t(7;10)(p22;p12)

Summary A girl with partial trisomy for the short arm of chromosome 10(p12pter) due to mal chromosome segregation in the father 46,XY,t(7;10)(p22;p12) is described. The major abnormalities in this case are: mottled skin, mid-facial hypoplasia, low percentiles for weight, length, and head circumference, and club feet.To whom offprint requests should be sent     

A new partial trisomy 12p with artery catheter vagus, congenital cataracts, external auditory canal, and no turbinate

We describe the prenatal diagnosis and fetal phenotype of partial trisomy 12 (p12-pter) transmitted from a maternal reciprocal translocation 6;12. Genetic analysis was conducted on umbilical cord blood for a fetus accompanied with tricuspid regurgitation and orbital hypertelorism from a 27-year-old gravida 4, para 1 after sonography at gestation 35weeks. The karyotype was unusual, with 46, XY, der (6), t (6;12) (p24; p12) mat. The pregnancy was terminated at 37 gestational weeks. The aborted fetus displayed dysmorphic features of a round flat face with prominent cheeks and high forehead, hypertelorism, short nose, broad and depressed nasal bridge, anteverted nares, deformed philtrum, open mouth, thin upper vermilion and broad everted lower lip, low-set ears and aural atresia, broad hands with simian creases, and a short neck. Fetal anatomy showed right artery catheter vagus, congenital cataract, no turbinate and external auditory canals. Through karyotype-phenotype analysis of this patient and a review of other reported cases, we believe this is a first report that expands the database of partial trisomy 12p, and is beneficial for future clinical genetic counseling. This study supports that phenotypic variability depends on the type and extent of the associated partial monosomy.