Partial trisomy 12q: a clinically recognisable syndrome. Genetic risks associated with translocations of chromosome 12q

Familial Congenital Facial Synkinesis Due to 12q Duplication: A Case Report and Literature Review

Inverse Marcus Gunn phenomenon is a rare form of congenital facial synkinesis in which jaw movement temporarily elicits ptosis, either unilateral or bilateral. This phenomenon is presumed to result from dysinnervation of facial muscles during development of the nervous system. We describe 2 brothers, both with inverse Marcus Gunn phenomenon in the context of multiple other congenital anomalies, all presumed secondary to a chromosomal abnormality involving 12q duplication and 1p36 deletion. Although a handful of familial cases of congenital facial synkinesis have been previously described, this is the first in which a genetic abnormality has been identified. Of the 4 genetic abnormalities previously described in association with congenital facial synkinesis (based on isolated case reports), 1 also involved duplication at the long arm of chromosome 12. We conclude that duplication of ≥1 of the roughly 44 protein-coding genes in the ∼6.3-Mb overlap region between the previously published case and our 2 patients is a likely genetic cause of congenital facial synkinesis.

Clinical delineation of a patient with trisomy 12q23q24

Trisomies of 12q23q24 have been described rarely in literature. Only a few case-reports have been published so far almost exclusively reporting on neonates or young infants. We present a 16-year-old patient with a trisomy of 12q23.3q24.3. Full phenotypic evaluation at this age comprised: severe growth retardation, developmental delay, intellectual disability and characteristic facial dysmorphisms. Initially, in the proband an insertion was cytogenetically mapped at chromosome 16: der(16)dir ins(16; 12)(q12.1; q24.11q24.31). The mother appeared carrier of a balanced insertion. Subsequent SNP-array analysis in the proband revealed a 16.3 Mb gain of 12q23.3 → 12q24.31. The clinical and molecular findings in this patient are compared with previous literature on cases with overlapping isolated 12q trisomies. The common phenotype observed consists of severe growth retardation, intellectual disability and characteristic facial features with hypertelorism, flat nasal bridge, down-turned mouth and poorly lobulated/low set ears. In addition, pediatric follow up into adolescence showed feeding difficulties requiring gastric tube feeding, recurrent otitis media, progressive contractures of joints and genito-renal problems, speech, communication and behavioral problems. These symptoms should be taken into account in the care and management of children with this condition.

Another patient with 12q13 microduplication

Interstitial duplication of the long arm of chromosome 12 is a rare cytogenetic condition. While several reports describe distal 12q duplication, only one case report of homogeneous, non-mosaic interstitial 12q13 duplication has been documented to date. The authors of that observation proposed that the associated phenotype represented a phenocopy of Wolf-Hirschhorn syndrome [Dallapiccola et al., 2009]. Only a few other recorded patients with deletion 12q13 → 12q21 involved mosaicism. We describe a new patient with homogeneous 12q13 duplication in a 6-year-old girl who, in early infancy, presented with dysmorphic features suggesting Wolf-Hirschhorn syndrome. What is potentially significant about this patient is that her facial phenotype evolved with age, suggesting a different gestalt in older patients.

TBX5 intragenic duplication: a family with an atypical Holt-Oram syndrome phenotype

Holt-Oram syndrome (HOS) is a rare autosomal dominant heart-hand syndrome due to mutations in the TBX5 transcription factor. Affected individuals can have structural cardiac defects and/or conduction abnormalities, and exclusively upper limb defects (typically bilateral, asymmetrical radial ray defects). TBX5 mutations reported include nonsense, missense, splicing mutations and exon deletions. Most result in a null allele and haploinsufficiency, but some impair nuclear localisation of TBX5 protein or disrupt its interaction with co-factors and downstream targets. We present a five generation family of nine affected individuals with an atypical HOS phenotype, consisting of ulnar ray defects (ulnar hypoplasia, short fifth fingers with clinodactyly) and very mild radial ray defects (short thumbs, bowing of the radius and dislocation of the radial head). The cardiac defects seen are those more rarely reported in HOS (atrioventricular septal defect, hypoplastic left heart syndrome, mitral valve disease and pulmonary stenosis). Conduction abnormalities include atrial fibrillation, atrial flutter and sick sinus syndrome. TBX5 mutation screening (exons 3-10) identified no mutations. Array comparative genomic hybridisation (CGH) revealed a 48 kb duplication at 12q24.21, encompassing exons 2-9 of the TBX5 gene, with breakpoints within introns 1-2 and 9-10. The duplication segregates with the phenotype in the family, and is likely to be pathogenic. This is the first known report of an intragenic duplication of TBX5 and its clinical effects; an atypical HOS phenotype. Further functional studies are needed to establish the effects of the duplication and pathogenic mechanism. All typical/atypical HOS cases should be screened for TBX5 exon duplications.

Cryptic duplication of 12q24.33 --> qter in a child with Angelman syndrome-simultaneous occurrence of two unrelated cytogenetic events

Simultaneous occurrence of two unrelated cytogenetic events is rare. We present a case of Angelman Syndrome (AS) deletion and 12q duplication in a child with a history of developmental delay, microcephaly, cerebral palsy, and seizures. Traditional cytogenetic studies showed a normal 46,XY karyotype. Fluorescence in situ hybridization (FISH) using probe D15S10 (AS region/15q11.2) revealed a deletion. In addition, we serendipitously detected 12q24.3 duplication by FISH with 12q subtelomere probe. He inherited this duplication from the mother who presented with a balanced translocation karyotype 46,XX,add(12)(q24.3).ish t(12;13)(q24.3;p11.2)(12qtel-;12qtel+,D13Z1/D21Z1+,RB1+). Array comparative genomic hybridization (array-CGH) revealed a duplication of three bacterial artificial chromosome (BAC) clones (RP11-46H11, RP11-386I8, and RP11-309H3) covering about 423 Kb of DNA sequence. The published 12q terminal duplication cases had a detectable segment by classical banded cytogenetics techniques. To our knowledge, this is the smallest 12q cryptic rearrangement characterized by array-CGH and confirmed by BAC-clone FISH analysis. Based on these findings, we attempted to separate the clinical features associated with AS deletion and those features that are probably due to partial 12q duplication. We then reviewed the genes mapped in the duplicated region using the human genome database to understand the clinical significance. A subsequent pregnancy in the mother revealed an apparently balanced t(12;13) karyotype. We compare our case with the published cases, and discuss the implications of our findings and its relevance in addressing genetic counseling issues.

Pure direct duplication (12)(q24.1 → q24.2) in a child with Marcus Gunn phenomenon and multiple congenital anomalies

Partial trisomy of the region 12q24.1-->q24.2 is rare and usually associated with other rearrangements. We report on the clinical and cytogenetic findings in a girl with a pure de novo direct duplication dup(12)(q24.1-->q24.2). She had developmental and growth retardation, facial dysmorphism with upslanting palpebral fissures, wide downturned mouth, short neck, and Marcus Gunn phenomenon. She also had single transverse creases, hypoplasia of the corpus callosum, and cardiac malformations consisting of a bicuspid aortic valve, multiple ventricular septal defects, and kinking of the aorta. The size of the duplication was characterized by molecular cytogenetics and comparative genomic hybridization (CGH) to be 11.5 Mb in size and extended from the BAC probe RP11-256L11 loci (108.2 Mb) +/- 1 Mb to the BAC probe RP11-665J20 loci (119.7 Mb) +/- 1 Mb. No such pure 12q24 duplication was detected out of the 23 patients reported in the literature with duplications in 12q region. Comparison with these reported 12q trisomies suggests the duplication dup(12)(q24.1-->q24.2) is associated with a recognizable phenotype consisting of characteristic facial dysmorphism, growth retardation, and cardiac malformation.

Prenatal findings and molecular cytogenetic analyses of partial trisomy 12q (12q24.32→qter) and partial monosomy 21q (21q22.2→qter)

OBJECTIVES

To present the prenatal findings and molecular cytogenetic analyses of partial trisomy 12q and partial monosomy 21q, and a review of the literature.

METHODS

Amniocentesis was performed at 23 gestational weeks in a 33-year-old woman because of abnormal sonographic findings. Amniocentesis revealed a derivative chromosome 21, or der(21), with a deletion on the region of 21q22.2 and an addendum of a small chromosomal segment of unknown origin. The maternal karyotype was subsequently found to be 46,XX,t(12;21)(q24.32;q22.2). Level II ultrasound showed microcephaly, micrognathia, a ventricular septal defect, and rocker-bottom feet. The pregnancy was terminated. A malformed infant was delivered without the phenotype of holoprosencephaly (HPE). Fluorescence in situ hybridization (FISH) and polymorphic DNA markers were used to investigate the involved chromosomal segments.

RESULTS

FISH study showed the absence of the signal of 21q subtelomeric probe and the presence of the signal of 12q subtelomeric probe in the der(21). The fetal karyotype was 46,XY,der(21) t(12;21)(q24.32;q22.2)mat. Genetic marker analysis showed a deletion at 21q22.2 and a breakpoint between D21S156 (present) and D21S1245 (absent). The deleted segment was measured about 4.5 Mb encompassing the HPE critical region.

CONCLUSIONS

Molecular genetic analyses help in determining the prenatally detected unbalanced cryptic translocation as well as parental balanced subtle translocation. A duplication of 12q24.32-->qter and a deletion of 21q22.2-->qter may be associated with prenatal sonographic findings of microcephaly, borderline ventriculomegaly and cerebellar hypoplasia, micrognathia, a ventricular septal defect, and rocker-bottom feet. Haploinsufficiency of the HPE critical region at 21q22.3 may not cause an HPE phenotype.

A girl with partial trisomy 12q24.31 inherited from her father and a possible novel syndrome transmitted from her mother

We report on a familial partial trisomy 12q in a girl and her father both of whom have an unbalanced translocation, der(16)t(12;16)(q24.31;q24.3), resulting in trisomy 12q24.31 --> qter and 16q subtelomere deletion. By comparing phenotypes of the girl and the father, we suggest that clinical features related to trisomy 12q24.31 --> qter are mild development delays, mild mental retardation, broad forehead, simplified ear helices, small mouth, and thin lips. The mother who has a normal karyotype has moderate mental retardation and a facial appearance similar to the girl. Both the girl and the mother have distinctive short, curly, and kinky hair. We suspect a possible new syndrome in the maternal family with mental retardation and curly, kinky hair. Thus, this patient likely inherited two discreet conditions causing mental retardation.

Prenatal diagnosis of partial trisomy 12q: clinical presentations and outcome

We present a pregnant woman with a fetus prenatally diagnosed as 46, XY,der(4) t(4;12) (q35.1; q21.2). This defect resulted from the unbalanced segregation of a paternal balanced translocation, t(4;12) (q35.1; q21.2). Prenatal ultrasound revealed borderline ventriculomegaly, a thick nuchal fold, pericardial effusion, arthrogryposis, a single umbilical artery, and micropenis. Fluorescence in situ hybridization (FISH) with whole chromosome painting probe and microarray-based comparative genomic hybridization analysis further confirmed chromosomal gain of terminal 12q. The woman had her pregnancy terminated at 20 weeks of gestational age. When compared with previously reported cases, the proband had characteristics common to the phenotypes of partial trisomy 12q, including an abnormal facial appearance and multiple anomalies. Additionally, this case had previously unreported phenotypes, such as arthrogryposis, a single umbilical artery, and a micropenis. Regarding the outcome of partial trisomy 12q, the fetuses carrying trisomies distal to 12q24 have a good chance of extended postnatal survival. In contrast, the cases with trisomies involving a larger amount of 12q likely die prenatally or within a few days after birth.

Two cousins with partial trisomy 12q and monosomy 12p recombinants of a familial pericentric inversion of the chromosome 12

Partial trisomy 12q and monosomy 12p lead to multiple malformation syndromes. Instead of trisomy 12q that has been reported as a clinically identifiable syndrome, monosomy 12p is characterized by a wide phenotypic spectrum. We report two cousins suffering from severe mental retardation, seizures, and dysmorphic features related to a trisomy 12q24.3-->qter and a monosomy 12p13-->pter resulting from a familial pericentric inversion of chromosome 12. In an attempt to improve the clinical delineation of these two syndromes, we compared our two patients with previous reports of these aneusomies. This review emphasizes the high frequency of familial translocations, including a breakpoint at 12q24 involved in trisomy 12q whereas monosomy 12p occurs most frequently de novo. Despite the poor specificity of the signs, this comparison allowed us to determine the clinical features present in more than 20% of patients with trisomy 12q or monosomy 12p. We particularly emphasize some consistent leading features of monosomy 12p, including microcephaly, dental, cardio-vascular, extremity, and sensorial abnormalities, initially not reported as recurrent in this syndrome.

Nonmosaic smallest duplication of 12q24.31-qter: The first reported case

Duplication of the terminal region of the long arm of chromosome 12 is not common. In 13 previous cases, duplication of this region was generally associated with deletions of the derivative chromosomes, larger sized duplications or mosaicism. We have studied a young man with a nonmosaic duplication of 12q24.31-qter translocated to chromosome 5pter. This is the first reported case of pure subtle duplication involving less than two terminal subbands of 12q24.31 to qter. The origin of this genetic material was confirmed by whole chromosome paints and subtelomere specific FISH probes. As both the subtelomere signals for 5p and 12q were present in the der(5) chromosome, it is unlikely that there was any loss of unique DNA sequences from the terminal region of chromosome 5p. This case is compared with 13 other reported cases with a duplication of the 12q terminal segment.

Subtle trisomy 12q24.3 and subtle monosomy 22q13.3: three new cases and review

The high resolution G-bands (850 bands) karyotype have made it possible to identify small chromosome anomalies (5 megabases) which are now microscopically visible. New techniques have been improved, such as the Fluorescent in situ hybridization (FISH) with subtelomeric probes, which can be employed to detect cryptic chromosome alterations not visible microscopically. We present three cases which had been remitted for a high resolution karyotype. The high resolution G-band karyotype and the FISH techniques led us to conclude that the three cases were carriers of a similar subtle chromosomal alteration. Case I is a new born female with developmental and psychomotor delay, hypotonia, and long limbs with arachnodactily. A high resolution G-band karyotype showed an abnormal chromosome 22. FISH techniques confirmed a der(22)t(12;22)(q24.31;q13.3). Case II is a 12-year-old girl, with growth retardation, long shaped face with thick eyebrows, smooth philtrum, and thin upper lip with severe mental retardation (still no language), with a phenotype very similar to that of his sister: long shaped face, thick eyebrows, smooth philtrum, and thin upper lip. A high resolution G-band karyotype also showed in Case II and III an abnormal chromosome 22, studied by FISH techniques which confirmed a der(22)t(12;22)(q24.3;q13.3) in both cases.

Neuroblastoma in a boy with MCA/MR syndrome, deletion 11q, and duplication 12q

Deletion 11q23-->qter and duplication 12q23-->qter are described in a boy with neuroblastoma, multiple congenital anomalies, and mental retardation. The patient has clinical manifestations of 11q deletion and 12q duplication syndromes. The possible involvement of the segment 11q23-->24 in the cause of the neuroblastoma is discussed.

Mosaicism for duplication 12q (12q13-->q24.2) in a dysmorphic male infant

We report the clinical findings in a boy with mosaicism for a duplication of chromosome 12q13.1-->q24.2. His clinical characteristics are very similar to previously reported mosaic duplications of the distal long arm of 12, as well as several cases with non-mosaic duplications. It is proposed that this represents a clinically distinguishable syndrome for 12q duplication, in mosaic or non-mosaic form.

Reassessment of a chromosome 12q+ marker by fluorescent in situ hybridization (FISH)

We present a case previously described by Jenkins et al. (1983) as atypical Down syndrome (DS). The initial diagnosis was first made on the basis of phenotypic and cytogenetic data. This analysis was supported by studies of superoxide dismutase (SOD1) activity that maps to band 21q22.1. Results from phenotypic, chromosome banding and SOD1 studies suggested a karyotype of 46,XX,-12,+t(12pter to 12qter::21q21 to 21q22.?2). Using fluorescent in situ hybridization (FISH) for chromosome painting with DNA libraries derived from sorted human chromosomes to stain selectively the chromosomes No. 21 and No. 12, we demonstrate that the marker chromosome 12q+ has no chromosome 21 content but it is derived from chromosome 12.

Eleven new cases of del(9p) and features from 80 cases

We report 11 cases of del(9p) and review 69 previously published ones. Of the 80 cases, 39 have a del(9p) as the sole anomaly. The symptoms are typical and diagnosis should be suspected at birth. The sex ratio does not appear to be unbalanced. A cardiac murmur is often present but surgery is rarely necessary. Mean IQ is 48. The number of reported cases with an associated trisomy has previously been underestimated. Death in infancy, owing mainly to gross visceral malformations, occurs more often in cases of del(9p) with another unbalanced chromosome segment (16/41) than in cases of del(9p) as the sole anomaly (1/39).

Duplication (12q) syndrome in female cousins, resulting from maternal (11;12) (p15.5;q24.2) translocations

We have studied female cousins with partial duplication of 12q. The cousins' mothers (who are sisters) and the maternal grandmother and great grandmother carried a balanced translocation between chromosomes 11 and 12. We have compared our patients with eight other reported cases of partial duplication of the same chromosome segment (12q24----12qter). Placement of the extra material seems to have little effect on the anomalies present; (only two other cases involved chromosome 11). We propose that our patients provide further evidence that duplication of 12q leads to a clinically identifiable syndrome.

Partial trisomy 12q: clinical and cytogenetic observations

High resolution chromosome banding showed a male infant with profound mental retardation, hypertonia and multiple congenital anomalies to have the karyotype 46,XY,-der (2),t(2;12)(q37.3;q24.13)pat. Most of the clinical findings were compatible with those of the previously described cases with partial trisomy 12q. Some of the clinical features seem to disappear with increasing age.

Partial trisomy 12q24.31----qter

Clinical details of a male child with the karyotype 46,XY,-4,+der(4),t(4;12) (p16;q24.31)mat are reported and compared with those of other known cases of partial trisomy of the distal region of 12q. This condition is apparently associated with mental and psychomotor retardation, widely spaced eyes, flat nasal bridge, low set ears, down-turned mouth, micrognathia, loose skin at the nape, widely spaced nipples, simian creases, clinodactyly, abnormalities of the genitourinary system, alterations in the sacrococcygeal region, and deformities of the lower limbs. In the majority of the reported cases, the break-point was in the 12q24 region and resulted from adjacent 1 segregation of a maternal balanced translocation.

Syndromes with lissencephaly. I: Miller-Dieker and Norman-Roberts syndromes and isolated lissencephaly

Lissencephaly (smooth-brain) is an abnormality of brain development characterized by incomplete neuronal migration and a smooth cerebral surface. At least 2, and possibly more, distinct pathological types occur, each associated with several distinct syndromes. In this paper, the manifestations of 3 disorders associated with type I (classical) lissencephaly are discussed, including the Miller-Dieker syndrome with or without deficiency of 17p13, Norman-Roberts syndrome, and isolated lissencephaly sequence.