The phenotypic and cytogenetic spectrum of partial trisomy 9

A new patient with trisomy for the chromosome segment 9pter----q22 is compared to 19 previously reported cases of partial trisomy 9. Manifestations such as microcephaly, prominent nasal root, bulbous nose, and down-turned corners of the mouth are common to patients with trisomic segments extending from 9p21 to 9q13, while intra-uterine growth retardation, cleft lip/palate, skeletal anomalies, and heart defects are more common with trisomic segments extending through 9q22-9q32. A graphic method illustrates this progression in the partial trisomy 9 malformation spectrum as the triplicated chromosome region extends from bands 9p21 to 9q32. More severe and random defects are observed with complete trisomy 9 or tetrasomy 9p, suggesting an extreme excess of material greatly increases developmental variability.     

Abnormal chromosome 9 in a neonate program. Report of three cases

We describe three cases with abnormal chromosome 9. Patient 1 shows translocation in a homologous chromosome, with a karyotype of 46,XX,t(9;9)(9pter----cen----9pter; 9qter----cen::9q13----9qter), 1qh+. This case has a variety of anomalies, including brain anomalies. Patient 2 shows a partial trisomy 9p with a karyotype of 47,XY,+del(9)(pter----q11:). The patient has the typical clinical features of 9p trisomy syndrome. Patient 3 is unique because of partial 9p tetrasomy mosaicism without phenotypic abnormalities; the karyotype is mos 46,XY/47,XY,+dic(9)(pter----cen----q21::q21----cen----pter).     

A boy with Down''s syndrome having recombinant chromosome 21 but no SOD-1 excess

A 5-year-old boy with Down's syndrome of mild phenotype is described. Chromosome studies revealed that the karyotype of the proband was 46,XY,rec(21),dup q,inv(21) (p11.2q22.1)mat, and the segment 21q22.1----21qter was trisomic. The erythrocyte superoxide dismutase-1 (SOD-1) was found to be normal, and so we conclude that SOD-1 excess is not necessarily observed in patients with Down's syndrome caused by partial 21 trisomy. It is suggested that the gene for SOD-1 is located on the more proximal segment of the sub-band 21q22.1.     

Partial trisomy 12q.

A partial trisomy 12q243 leads to qter resulting from a maternal balanced translocation, 46,XX,t(9;12)(p243;q243) was detected in a male newborn with multiple congenital abnormalities. The maternal grandmother was also a carrier of the 9;12 translocation. Our patient exhibited a number of clinica features similar to two others reported, who were also trisomic for the distal part of 12q. Aberrations of chromosome 12 are very rare. There have been only two reports of partial trisomy 12q, both the result of a familial translocation. We describe a third unbalanced case.     

Antenatal manifestations of Smith-Lemli-Opitz (RSH) syndrome: a retrospective survey of 30 cases

We report on a case of an interstitial duplication of 11q in a patient with developmental delay and in his moderately delayed mother. Partial trisomy 11q is well documented in the literature with most cases involving the distal region of the long arm of chromosome 11. In almost all cases, this trisomy is associated with monosomy of the second chromosome involved in the parental translocation. The most common, partial 11q and 22q trisomy syndrome, is observed in offspring of t(11;22)(q23;q11.2) carriers from a 3:1 tertiary trisomic malsegregation. We found only two previous reports of pure partial trisomy 11q in the literature. Comparison of the clinical findings of our patient and another single published report of duplication in the same segment of chromosome 11 suggests that the duplication of this region manifests mild phenotypic abnormalities.     

Mirror-symmetric duplicated chromosome 21q with minor proximal deletion, and with neocentromere in a child without the classical Down syndrome phenotype

We report on a mentally retarded child with multiple minor anomalies and an unusually rearranged chromosome 21. This der(21) chromosome has a deletion of 21p and of proximal 21q, whereas the main portion of 21q is duplicated leading to a mirror-symmetric appearance with the mirror axis at the breakpoint. The centromere is only characterized by a secondary constriction (with a centromeric index of a G chromosome) at an unexpected distal position, but fluorescence in situ hybridization (FISH) with either chromosome specific or with all human centromeres alpha satellite DNA shows no cross hybridization. Thus, the marker chromosome represents a further example of an "analphoid marker with neocentromere." Molecular analysis using polymorphic markers on chromosome 21 verified a very small monosomic segment of the proximal long arm of chromosome 21, and additionally trisomy of the remaining distal segment. Although trisomic for almost the entire 21q arm, our patient shows no classical Down syndrome phenotype, but only a few minor anomalies found in trisomy 21 and in monosomy of proximal 21q, respectively.     

Three cases of partial trisomy 9q in one generation due to maternal reciprocal t(6;8;9) translocation

A family is described in which three siblings had congenital abnormalities consistent with partial trisomy 9q syndrome. Karyotyping indicated that the mother was a carrier of two separate balanced reciprocal translocations involving three chromosomes (46,XX,t (6;8;9)(6q27;8p23;9q32;9q13] resulting from four breakpoints. The three siblings had inherited the der(8) from their mother and hence were partially trisomic for 9q32----9qter and partially monosomic for 8p23----8pter (46,XX,der(8),t(8;9)(p23;q32)mat). The clinical features of the three cases were comparable to those reported in the literature.     

Anatomical studies of a boy trisomic for the distal portion of 13q

A boy trisomic for the distal portion of 13q was dissected in detail and compared to 8 cases of complete trisomy 13 previously studied in our laboratory. The comparison shows that the partial trisomy 13q case did not correspond well to a muscle phenotype based on 6 variations common trisomy 13, but rather to a larger muscle phenotype that included variations less frequently observed in complete trisomy 13. Additional cases of partial trisomy 13 must be studied before these findings can be related to specific portions of chromosome 13.     

Subtelomeric familial translocation t(2;7)(q37;q35) leading to partial trisomy 7q35-->qter: molecular cytogenetic analysis and clinical phenotype in two generations

Few patients with trisomy of the most distal region of chromosome 7q have been described. We report on a familial translocation t(2;7)(q37;q35) leading to trisomy 7q35-->7qter in a child and her paternal uncle and a minimal deletion of distal 2q as demonstrated by FISH with probes located in the chromosome 2q subtelomeric region. The clinical phenotype included macrocephaly and low-set ears, also found in other reported patients trisomic for the distal part of chromosome 7q. Phenotypic findings probably useful for the clinical diagnosis include normal size at birth, large head with frontal bossing, low-set ears of normal shape, small nose and low nasal bridge, feeding difficulties in infancy, and severe neurodevelopmental delay.     

Trisomy 6qter

A previously reported patient with trisomy for the distal part of 6q was shown by R-banding to be trisomic for 6q26qter, due to a t(6;22)(q26;p12) mat. Altogether nine patients with 6qter trisomy have been reported. The main features of the 6qter trisomy syndrome are: severe mental and growth retardation; acrocephaly and brachycephaly; a carp-shaped mouth; micrognathia; a very short neck with unusual anterior webbing; joint contractures; the absence of severe inner organ malformations; and survival into adulthood.     

Mirror‐symmetric duplicated chromosome 21q with minor proximal deletion,and with neocentromere in a child without the classical Down syndrome phenotype

We report on a mentally retarded child with multiple minor anomalies and an unusually rearranged chromosome 21. This der(21) chromosome has a deletion of 21p and of proximal 21q, whereas the main portion of 21q is duplicated leading to a mirror‐symmetric appearance with the mirror axis at the breakpoint. The centromere is only characterized by a secondary constriction (with a centromeric index of a G chromosome) at an unexpected distal position, but fluorescence in situ hybridization (FISH) with either chromosome specific or with all human centromeres alpha satellite DNA shows no cross hybridization. Thus, the marker chromosome represents a further example of an “analphoid marker with neocentromere.” Molecular analysis using polymorphic markers on chromosome 21 verified a very small monosomic segment of the proximal long arm of chromosome 21, and additionally trisomy of the remaining distal segment. Although trisomic for almost the entire 21q arm, our patient shows no classical Down syndrome phenotype, but only a few minor anomalies found in trisomy 21 and in monosomy of proximal 21q, respectively. Am. J. Med. Genet. 91:116–122, 2000. © 2000 Wiley‐Liss, Inc.     

A summary of 7q interstitial deletions and exclusion mapping of the gene for beta-glucuronidase.

Three patients are described with different phenotypes and differing de novo interstitial deletions of the long arm of a chromosome 7. The first patient has a deletion with loss of the proximal 7q11.23 band. Only three other cases have been reported with this particular deletion. Our second case shows mild dysmorphism similar to the other four patients reported with deletion of bands 7q21.12----21.3. Our third patient has a deletion of the 7q22.1----32.2 segment and has many of the phenotypic features of the other reported cases of del 7q22----32. GUSB, the gene for beta-glucuronidase, has been localised to the 7cen----q22 region. Analysis of beta-glucuronidase levels in blood leucocytes of our patients has helped more precisely to assign this gene locus to 7q21.11 or 7q22.1.     

Subtelomeric familial translocation t(2;7)(q37;q35) leading to partial trisomy 7q35→qter: Molecular cytogenetic analysis and clinical phenotype in two generations

Few patients with trisomy of the most distal region of chromosome 7q have been described. We report on a familial translocation t(2;7)(q37;q35) leading to trisomy 7q35→7qter in a child and her paternal uncle and a minimal deletion of distal 2q as demonstrated by FISH with probes located in the chromosome 2q subtelomeric region. The clinical phenotype included macrocephaly and low‐set ears, also found in other reported patients trisomic for the distal part of chromosome 7q. Phenotypic findings probably useful for the clinical diagnosis include normal size at birth, large head with frontal bossing, low‐set ears of normal shape, small nose and low nasal bridge, feeding difficulties in infancy, and severe neurodevelopmental delay. Am. J. Med. Genet. 93:349–354, 2000. © 2000 Wiley‐Liss, Inc.     

Virilization of the external genitalia and severe mental retardation in a girl with an unbalanced translocation 1;18

A female infant with dysmorphic facial features, psychomotor retardation, and clitoris hypertrophy is described. Molecular cytogenetic analyses revealed a de novo unbalanced translocation, causing partial monosomy 1p36 and partial trisomy 18q22. Monosomy 1p was confirmed by FISH, and trisomy of the distal part of chromosome 18q was demonstrated by microFISH. Gene copy number changes in these chromosomal regions were determined by array-CGH. The absence of a number of facial dysmorphic signs, and the presence of clitoris hypertrophy indicate that the combination of a del(1p36->pter) with a dup(18q22->qter) may lead to a unique phenotypic constellation. The findings at birth and at age 12 years in our patient are compared with genotype-phenotype correlations discussed in the literature.     

Trisomy 2q35-q37 due to insertion of 2q material into 17q25: clinical, cytogenetic, and molecular cytogenetic characterization

We present a 7-year-old boy with growth retardation, developmental and mental delay, and minor physical abnormalities. The patient had a male karyotype with duplicated material of unknown origin in the long arm of chromosome 17. The origin of the duplicated material was clarified by fluorescence in situ hybridization. Forward chromosome painting showed that the extra material originated from chromosome 2, which was inserted into 17q25. Further characterization of the aberrant chromosome 17 by microdissection and reverse chromosome painting revealed a duplication of bands 2q35 to q37.1. To our knowledge, no other individual with a duplication of this small segment has been described so far. The clinical findings of 13 cases with isolated trisomy 2q are reviewed in relation to the size of the duplicated region. Functional analysis of the duplicated 2q region suggests that critical loci for visceral and central nervous system development in distal trisomy 2q are proximal to 2q33.     

Molecular cytogenetic characterisation of partial trisomy 9q in a case with pyloric stenosis and a review

Partial trisomy 9q represents a rare and heterogeneous group of chromosomal aberrations characterised by various clinical features including pyloric stenosis. Here, we describe the case of a 1 year old female patient with different dysmorphic features including pyloric stenosis and prenatally detected partial trisomy 9q. This partial trisomy 9q has been analysed in detail to determine the size of the duplication and to characterise the chromosomal breakpoints. According to the data gained by different molecular cytogenetic techniques, such as fluorescence in situ hybridisation (FISH) with whole and partial chromosome painting probes, yeast artificial chromosome (YAC) probes, and comparative genomic hybridisation (CGH), the derivative chromosome 9 can be described as dup(9)(pter→q22.1::q31.1→q22.1::q31.1→ q22.1::q31.1→qter). Four breakpoint spanning YACs have been identified (y806f02, y906g6, y945f5, and y747b3) for the proximal breakpoint. According to this new case and previously published data, the recently postulated putative critical region for pyloric stenosis can be narrowed down to the subbands 9q22.1-q31.1 and is the result of either partial trisomy of gene(s) located in this region or a gene disrupted in 9q31.


Keywords: partial trisomy 9q; pyloric stenosis; FISH; CGH     

Trisomy 10qter confirmed by in situ hybridisation.

We report a boy with multiple congenital anomalies compatible with trisomy for the distal region of the long arm of chromosome 10 and a male karyotype with one 18p+. In situ hybridisation with a cDNA for ornithine aminotransferase (OAT), whose locus maps to 10q26, confirmed the clinical suspicion of distal trisomy 10q. Subterminal localisation of the labelling signals on chromosome 10 and on the der(18) indicated the localisation of the OAT locus in the proximal part of 10q26. Two clusters of labelling signals were also found on the pericentromeric and proximal portion of the X chromosome short arm, thus confirming the presence in this region of two non-adjacent OAT pseudogenes. The phenotypic similarities of this patient to previously reported cases provide further support for the delineation of trisomy 10qter as a specific, clinically recognisable syndrome.     

Karyotype/phenotype correlation in partial trisomies of the long arm of chromosome 16: case report and review of literature

Trisomy 16q is a clinically recognizable entity presenting with a wide spectrum of abnormalities. Only five infants with a diagnosis of partial trisomy 16q13?→?qter have been previously reported, and all died during the first year of life. We report the clinical and molecular cytogenetic findings in a patient with trisomy 16q13?→?qter due to the presence of a supernumerary marker chromosome (SMC). The child presented with microcephaly, ambiguous genitalia, cardiac malformations and dysmorphic features. Cytogenetic investigation using GTG-banding, spectral karyotyping (SKY) and fluorescence in situ hybridization analyses revealed an SMC of maternal origin with karyotype der(15)t(15;16)(q13;q13). Specific genotype-phenotype correlations among different segments of the 16q region cannot yet be defined. We suggest that the involvement of the entire region spanning from 16q11 to 16q22 is necessary for the characteristic phenotype of the trisomy 16q.     

Partial trisomy 14q24 leads to qter.

A newborn male with partial trisomy for the distal part of the long arm of chromosome 14 (14q24 leads to qter) is described. The anomaly arose as an adjacent 1 meiotic segregation product from a balanced translocation t(11;14) (q25;q24) in the mother (figure). To our knowledge only one previous case involving the same segment has been reported. The karyotype was confirmed as 46,XY,der(11),t(11;14)(q25;q24) mat.     

A child with a recombinant of chromosome 8 inherited from her carrier mother.

A female child with mental retardation and dysmorphic features was found to have a duplication deficiency of chromosome 8: rec(8)dup q,inv(8)(p23q24), a recombinant product derived from a familial pericentric inversion, inv(8)(p23q24)mat. Clinical features of this previously undescribed inversion product are compared with other reported cases of partial trisomy for the distal long arm of chromosome 8, since this segment is thought to be primarily responsible for the phenotypic features of the trisomy 8 syndrome.