Smallest terminal deletion of the long arm of chromosome 2 in a mildly affected boy

A rare case of 2q37 deletion syndrome presented with patent foramen ovale

This case report presents a 3-year-old female child diagnosed with 2q37 deletion syndrome and patent foramen ovale, and the improvement in hypotonia and gross motor delay after 1 year of physical therapy. This case highlights the importance of thorough examination and diagnostic testing in identifying underlying causes of developmental delays.

Genotype and phenotype correlation in 103 individuals with 2q37 deletion syndrome reveals incomplete penetrance and supports HDAC4 as the primary genetic contributor

The 2q37 deletion syndrome, also described in the literature as brachydactyly-mental retardation syndrome (MIM 600430), is caused by deletion or haploinsufficiency of the HDAC4 gene, which encodes the histone deacetylase 4 protein. Although the most commonly described hallmark features of the 2q37 deletion syndrome include brachydactyly type E, developmental delay, obesity, autistic features, and craniofacial or skeletal dysmorphism, a literature review of 101 published cases plus two newly reported individuals indicates that there is a high degree of variability in the presence of some of the features that are considered the most characteristic of the syndrome: overweight and obesity (34%), cognitive-behavioral issues (79%), dysmorphic craniofacial features (86%), and type E brachydactyly (48%). These features overlap with other neurodevelopmental conditions, including Smith-Magenis syndrome (SMS), and may be incompletely penetrant or demonstrate variable expressivity, depending on the specific chromosomal anomaly. With the advent of fluorescence in situ hybridization (FISH), array-based comparative genomic hybridization, and next-generation DNA sequencing, more detailed molecular diagnoses are possible than in years past, enabling refined characterization of the genotype-phenotype correlation for subjects with 2q37 deletions. In addition, investigations into molecular and gene expression networks are expanding in neurodevelopmental conditions, and we surveyed HDAC4 downstream gene expression by quantitative real-time polymerase chain reaction, further implicating HDAC4 in its role in the regulation of RAI1. Correlation of clinical data defining the impact on downstream gene expression and the potential clinical associations across neurodevelopment will improve our understanding of these complex conditions and potentially lead to common therapeutic approaches.

Prenatal diagnosis of microdeletion 16p13.11 combination with partial monosomy of 2q37.1-qter and partial trisomy of 7p15.3-pter in a fetus with bilateral ventriculomegaly, agenesis of corpus callosum, and polydactyly

OBJECTIVE

To present a prenatal diagnosis of microdeletion 16p13.11 with partial monosomy of 2q37.1-qter and partial trisomy of 7p15.3-pter in a fetus with bilateral ventriculomegaly, agenesis of corpus callosum, and polydactyly.

CASE REPORT

A 41-year-old well-being Taiwanese, nulligravida woman received amniocentesis at a gestational age of 18 weeks for advanced maternal age. The fetus' karyotype showed 46,XY,der(2)t(2;7)(q36.2;p15.1). Both parents also received cytogenetic examinations and the mother's karyotype revealed 46,XX,t(2;7)(2q36.2;p15.1). High-resolution ultrasound showed the fetus had bilateral ventriculomegaly, agenesis of corpus callosum, and polydactyly of the right hand. After the termination of this pregnancy, the whole genome oligonucleotide-base array comparative genomic hybridization (CGH) by using fetal skin cells demonstrated a 8.44-Mb deletion at 2q37.1 (234602276-243041305), a 22.8-Mb duplication (65558-22869338) at 7p15.3, and an additional 1.32-Mb deletion (14968855-16292235) at 16p13.11.

CONCLUSION

Array CGH is a useful tool not only to discover the genomic imbalance at the breakpoints as well as to detect unexpectedly complex rearrangements in other chromosomes. Our case also provided evidence that genomic aberration at chromosome 16p13.11 involves in the formation of polydactyly.

Deletion 2q37: an identifiable clinical syndrome with mental retardation and autism

Terminal deletion of the long arm of chromosome 2 is a rare chromosomal disorder characterized by low birth weight, delayed somatic and mental development, craniofacial defects, short neck, heart and lung congenital defects, and autistic features. We report on a girl with 46,XX.ish del(2)(q37.1) de novo karyotype, mental retardation, dysmorphic features, gastrointestinal anomalies, and autistic traits and compare her clinical manifestations with patients with the same deletion previously described in literature.

Chromosome 2q37 deletion: clinical and molecular aspects

Terminal deletions of chromosome 2 with breakpoints at or within band 2q37, ranging from visible abnormalities to cryptic, subtelomeric deletions, have been recognized with increasing frequency among children with mild-moderate mental retardation, characteristic facial appearance, and behavioral manifestations which often place them on the autism spectrum. The stereotypic facial characteristics include prominent forehead, thin, highly arched eyebrows, depressed nasal bridge, full cheeks, deficient nasal alae and prominent columella, thin upper lip, and various minor anomalies of the pinnae. Abnormal nipples, including inverted nipples, have been reported in a number of cases. CNS, ocular, cardiac, gastrointestinal, renal, and other GU anomalies have been noted in nearly one-third of patients. Of note, coarctation or hypoplasia of the aorta has been described in several affected children. Wilms tumor, renal dysplasia, and tracheomalacia have been reported only with the most proximal breakpoint at band 2q37.1 while a range of GI anomalies, pyloric stenosis, and diaphragmatic defects have been reported with breakpoints throughout the region. A subset of patients with the most distal deletion present phenotypic features which mimic Albright hereditary osteodystrophy (AHO). In addition to the AHO-like phenotype, later onset findings include seizures and cystic kidneys. Timely diagnosis of this recognizable syndrome provides a basis for genetic counseling, appropriate surveillance, and intervention, and avoids unnecessary and expensive diagnostic testing.

Molecular delineation of deletions on 2q37.3 in three cases with an Albright hereditary osteodystrophy-like phenotype

A minority of the reported cases of terminal 2q37 deletion clinically resemble Albright hereditary osteodystrophy (AHO)/pseudopseudohypoparathyroidism and have only mild-to-moderate mental retardation. Our molecular and cytogenetic fluorescence in situ hybridization (FISH) findings on an additional three patients further reduce the size of the minimal critical region deleted in this syndrome to about 3 Mb. This region includes the G-protein-coupled receptor 35 (GPR35), glypican 1 (GPC1), and serine/threonine protein kinase 25 (STK25) genes on 2q37.3. We have further defined several polymorphic variants within the coding region and flanking regions of GPR35 gene, which could potentially be useful for rapid detection of GPR35 gene deletion. We postulate that the absence of GPR35 may, at least partly, account for the phenotypic resemblance to the AHO. We also believe that the deletion of GPR35 could be responsible for the entity brachydactyly mental retardation syndrome (OMIM #600430), which was coined based on the above minority of patients with terminal 2q37 deletion. We recommend that every patient with AHO phenotype should undergo 2q subtelomeric FISH screen and subsequently a molecular study on the GPR35 gene. GPC1 and/or STK25 haploinsufficiency may also contribute to the AHO-like phenotype.

Molecular cytogenetic analysis of five 2q37 deletions: refining the brachydactyly candidate region

Deletions of the 2q37 region are associated with a recognizable pattern of MCA/MR so-called the AHO-like syndrome. Brachydactyly is a variable but characteristic feature of this clinical entity. Here we report on five cases of cytogenetically visible de novo deletions of this 2q37 chromosome region. Using FISH, we characterized at the molecular level the breakpoints of these deletions using a set of 15 BACs, PACs and YACs. In four patients, terminal deletions of variable size ranged between 6.2 and 10 Mb. The fifth patient had an interstitial deletion with an AHO-like phenotype including brachydactyly. These findings when compared to previous observations allowed us to narrow down the brachydactyly critical region between BACs RP11-585E12 and RP11-351E10. It contains HDAC4 and STK25 candidate genes loci.

Chromosome 2q terminal deletion: report of 6 new patients and review of phenotype-breakpoint correlations in 66 individuals

We report a new patient with terminal deletion of chromosome 2 with breakpoint at 2q36 and five additional new patients with 2q terminal deletion with breakpoint at 2q37. Hemidiaphragmatic hernia is a novel finding in one patient with a breakpoint at 2q37.1. In comparing these patients to 60 previously reported individuals with 2q terminal deletions, certain physical abnormalities are loosely associated with positions of breakpoint. For example, facial features (e.g., prominent forehead, depressed nasal bridge, and dysmorphic ears and nose), short stature, and short hands and feet were frequent in patients with breakpoints at or proximal to 2q37.3. Reports of horseshoe kidney and Wilms tumor were limited to patients with a breakpoint at 2q37.1, and structural brain anomalies and tracheal anomalies were reported only in patients with breakpoints at or proximal to 2q37.1. Cleft palate was reported only in patients with the most proximal breakpoints (2q36 or 2q35). Neurological effects including developmental delay, mental retardation, autistic-like behavior, and hypotonia were typical in this patient population but did not stratify in severity according to breakpoint. Terminal deletion of the long arm of chromosome 2 should be considered in the infant with marked hypotonia, poor feeding, gastroesophageal reflux, and growth delay, and the older child with developmental delay, autistic behavior, and the characteristic facial and integumentary features described herein. Assignment of clinical features to specific breakpoints and refinement of predictive value may be useful in counseling.

Molecular characterization of a cryptic 2q37 deletion in a patient with Albright hereditary osteodystrophy-like phenotype

The Albright hereditary osteodystrophy-like (AHO-like) syndrome was recently defined as a rare dysmorphic syndrome including brachymetaphalangism and mental retardation. This phenotype occurs in Albright hereditary osteodystrophy (AHO) but unlike it, the level of the Gs alpha protein activity is not reduced. To date 59 patients with these clinical and biochemical features have been reported, and for the majority of them (57/59) a cytogenetically visible 2q37 deletion has been observed. We report a new case of typical AHO-like syndrome with normal karyotype. Using the polymorphic marker D2S125 we found a loss of heterozygosity suggestive of a de novo 2q37 deletion of maternal origin. This hypothesis was confirmed by FISH analysis with a subtelomeric 2q probe containing the D2S90 marker. Genotypic analysis allowed us to map the proximal breakpoint of the subtelomeric deletion within an interval delimited by D2S2338 (present) and D2S2253 (deleted). This 2q subtelomeric deletion as small as 4 Mb is to date the smallest one observed in association with a typical AHO-like phenotype, and allows us to move the centromeric boundary of the AHO-like critical region by 750 kb towards the 2q telomere.

Familial cryptic translocation (2;17) ascertained through recurrent spontaneous abortions

We report a young woman who presented with a reproductive history of three recurrent spontaneous abortions (RSA) and two neonatal deaths. Comparative genomic hybridization (CGH) was used to determine the chromosomal composition of the patient's last miscarriage. It showed the presence of monosomy for the distal end of chromosome 2 long arm (segment 2q37.2 to qter) and trisomy for the distal end of chromosome 17 long arm (segment 17q25 to qter). The mother was found to be a carrier for a cryptic translocation between chromosomes 2 and 17 long arms by fluorescence in situ hybridization using a subtelomeric probe for 17q. Retrospective CGH analysis on one baby who died neonatally showed that he had inherited the maternal translocation in the same unbalanced state as the last pregnancy loss. His detailed postmortem examination is reported.

Characterization of terminal chromosome anomalies using multisubtelomere FISH

Telomeric repeat sequences (TTAGGG) are known to cap the termini of every human chromosome. Proximal to these repeat sequences are chromosome-specific repeat sequences, which in turn are distal to gene-rich regions. Submicroscopic, subtle, or cryptic abnormalities in these regions can now be investigated using commercial probe sets for all of the chromosome-specific subtelomeric regions of the human genome. Using this technology, previously unidentified genomic imbalance has been found in a proportion of patients with idiopathic developmental delay and learning difficulties. We have used these probe sets to investigate cases with apparently terminal anomalies detected on G-banded chromosome analysis. As a result of such investigations, we have found that 3 (19%) of 16 apparently terminal deletion cases were the result of more complex rearrangements involving other chromosome subtelomeres. The remaining 13 cases contained no chromosome-specific subtelomere repeats on the deleted arm, but in all 16 cases, the TTAGGG telomere repeat cap was present. A further case was investigated where extra material was found in the terminal region of the chromosome 12 short arm, found to represent a complex inversion/duplication/deletion rearrangement. Investigation of all cases with terminal anomalies, including apparently terminal deletions, is likely to uncover further cases involving complex rearrangements and should lead to a greater understanding of the mechanisms by which these abnormalities arise.

Recombinants of intrachromosomal transposition of subtelomeres in chromosomes 1 and 2: a cause of minute terminal chromosomal imbalances

Two cases of submicroscopic recombinants of intrachromosomal transposition of telomeres, one each from chromosome 1 and 2 are described. Meiotic crossing-over would generate the recombinants from these reciprocal rearrangements. In both cases, which were detected by FISH with subtelomeric probes, there is a minute deletion of the qter region and a second presence of the pter subtelomeric region on the respective qter, i.e., a duplication of 1pter or 2pter respectively. The deletion on 2qter (case 2) was confirmed by microsatellite inheritance and was of paternal origin, but in case 1 there was no detectable 1q deletion other than of the subtelomeric probe, and parental origin could not be determined. The present case 2 with del(2qter)/dup(2pter) shares many features with reported cases of simple deletion (2qter) but did not have features of Albright hereditary osteodystrophy, which are seen in half of such deletion patients. The clinical features present in case 1 were similar to those of the previously reported case of a submicroscopic 1qter deletion but also to cases with microscopically visible 1qter deletions, presumably because of gene enrichment in subtelomeric regions. Recombinants of such intrachromosomal subtelomere transpositions detected by subtelomeric probes may comprise up to 10% of submicroscopic pter or qter deletion cases. Other cases of this unusual mechanism may be detected with more common use of subtelomeric probes. It is suggested the bouquet associations of telomeres in early meiosis may facilitate such unusual rearrangements.

Deletion of 2q37 and duplication of 10q24: two cases in the same family and review of the literature

We describe two patients (first cousins, once removed) with an unusual head shape, high arched palate, flat nasal bridge, abnormal ears, hand and feet abnormalities and other anomalies. The patients were ascertained independently and it was initially unknown that they were related to each other. Cytogenetic and fluorescent in situ hybridization (FISH) analysis identified a der(2)t(2;10)(q37.3;q24.1) unbalanced translocation resulting in loss of 2q37.3-qter and duplication 10q24.1-qter. The clinical features of these two patients are compared with previously described cases of 2q deletion and 10q duplication. These patients also emphasize the difficulty in some families of understanding and sharing genetic information and in the difficulties in obtaining an accurate pedigree in a genetics clinic.

Microdeletion of chromosome sub-band 2q37.3 in two patients with abnormal situs viscerum

We report on two cases of microdeletion of chromosome sub-band 2q37.3 with abnormal situs viscerum. The first patient had dextrocardia, duodenal and jejunal atresia, and an abdominal hernia. The liver was in the left upper quadrant, stomach in the right upper quadrant. In contrast anema the ascending colon was in the left, and descending colon on the right, with an area of atresia in the mid-jejunum. The second patient had malrotation and malposition of large and small bowel, with most of the bowels positioned above the liver and spleen. There was incomplete rotation of the cecum. The right kidney was malrotated and mal-positioned. The finding of 2q37.3 deletion in both patients implies that a locus or loci involved in the development of normal body situs lies within this chromosome region. Molecular cytogenetic evaluation for a possible 2q37.3 deletion should be considered in patients with abnormal situs viscerum.

Deletion of chromosome 2q37 and autism: a distinct subtype?

Several reports have described the occurrence of chromosome abnormalities in autism, a neuro-developmental disorder characterized by social deficits, communication impairment, and a restricted range of interests. These include the fragile X abnormality and 15q duplications. In this report, we describe two cases of chromosome 2q37 and review the literature on this topic. We propose that deletion of the distal portion of the long arm of chromosome 2 (2q37) may be associated with some cases of autism and with a distinct phenotype. Increased awareness of the dysmorphic features associated with 2q37 deletions may aid in the molecular genetic analysis of this chromosome anomaly and clarify its relationship with autism.

RDCI, the vasoactive intestinal peptide receptor: a candidate gene for the features of Albright hereditary osteodystrophy associated with deletion of 2q37

Albright hereditary osteodystrophy (AHO) is an autosomal dominant disorder characterised by the presence of brachymetaphalangism, short stature, obesity, and mental retardation. Variable biochemical changes many represent either pseudohypoparathyroidism (PHP) owing to resistance to parathormone (PTH) or pseudopseudohypoparathyroidism (PPHP) with no hormone resistance. In most cases of AHO, reduced levels of Gs alpha have been found and a number of deactivating mutations in the gene for Gs alpha located on chromosome 20q13 have been described. Recently a number of people with an AHO-like phenotype have been reported in whom a deletion of chromosomal region 2q37 has been found in the absence of biochemical abnormalities or a reduction in Gs alpha activity. We present a further female patient with a cytogenetically visible deletion of 2q37, an AHO-like phenotype, and unusual biochemistry suggesting moderate PTH resistance. The vasoactive intestinal peptide receptor (RDCI) has recently been mapped to 2q37 and we propose that this is a candidate gene, hemizygosity of which affects signal transduction and leads to the AHO-like phenotype found in patients with 2q37 deletions.

Deletion or triplication of the alpha 3 (VI) collagen gene in three patients with 2q37 chromosome aberrations and symptoms of collagen-related disorders

Two new cases of del(2)(q37.1) and one case of partial trp(2)(q37) are studied by FISH with cosmid probes from the COL6A3 and PAX3 genes mapped in 2q37.3 and 2q36, respectively. While the PAX3 gene dosage appeared unaffected, the COL6A3 gene was found to be deleted and triplicated, respectively. This finding could explain features of connective tissue disorders such as joint laxity and hypotonia or joint stiffness and epiphyseal dysplasia, particularly documented by congenital dislocation of the radial head. Karyotype-phenotype correlations with reference to published cases are discussed.

Clinical phenotype associated with terminal 2q37 deletion

Three children with deletions of the terminal portion of the long arm of chromosome 2 [del (2) (q37)] are described and their clinical findings compared to published cases of 2q terminal deletions. Common clinical findings include development delay, macrocephaly, frontal bossing, depressed nasal bridge and cardiac anomaly. Hypotonia and repetitive behavior are also seen during different times of development. The facial characteristics of children with 2q terminal deletions are not uniform, but development delay is a constant finding. Chromosomal analysis of such children using high resolution banding may uncover the diagnosis of a small chromosomal deletion.

Albright hereditary osteodystrophy and del(2) (q37.3) in four unrelated individuals

Albright hereditary osteodystrophy (AHO) is a condition with characteristic physical findings (short stature, obesity, round face, brachydactyly) but variable biochemical changes (pseudohypoparathyroidism, pseudopseudohypoparathyroidism). Most patients with AHO have decreased activity of the guanine nucleotide-binding protein (GS protein) that stimulates adenylyl cyclase. The gene encoding the alpha subunit of the GS protein (GNAS1) has been mapped to the long arm of chromosome 20. We describe 4 unrelated individuals with apparent AHO, associated with small terminal deletions of chromosome 2. All 4 patients had normal serum calcium levels consistent with pseudopseudohypoparathyroidism. Del(2) (q37) is the first consistent karyotypic abnormality that has been documented in AHO [Phelan et al., 1993: Am J Hum Genet 53:484]. The finding of the same small terminal deletion in 4 unrelated individuals with a similar phenotype suggests that a gene locus in the 2q37 region is important in the pathogenesis of Albright syndrome. The association of Albright syndrome and the GNAS1 locus on chromosome 20 is well documented. The observation of a second potential disease locus on chromosome 2 may help explain the heterogeneity observed in this disorder.

Deletion of chromosome 2q24-q31 causes characteristic digital anomalies: case report and review

We describe a newborn boy with multiple anomalies, including bilateral split foot and an interstitial deletion of chromosome 2 (q24.2-q31.1). Four additional cases in 2 families involving similar deletions have been reported. Bilateral digital anomalies of hands and feet were seen in all 5 cases, including a wide cleft between the first and second toes, wide halluces, brachysyndactyly of the toes, and camptodactyly of the fingers. Other common manifestations have included postnatal growth and mental retardation, microcephaly, down-slanting palpebral fissures, micrognathia, and apparently low-set ears. Bilateral digital anomalies were reported in 22 of 24 cases with deletions including at least part of region 2q24-q31. Digital anomalies were not prevalent in 18 patients with deletions of chromosome 2q not overlapping 2q24-q31. 2q31.1 appears to be the common deleted segment in all cases with significant digital anomalies, which implies the existence of one or more genes involved in distal limb morphogenesis in this region. HOXD13 and EVX2, located in the proximity of 2q31, were not deleted in our patient by Southern analysis. Bilateral digital malformations of the hands and feet associated with other anomalies should be evaluated by chromosome analysis focused at the 2q24-q31 region.

Small terminal deletions of the long arm of chromosome 2: two new cases

We report on 2 girls with small de novo terminal deletions of the long arm of chromosome 2 and breakpoints within q37. Four cases with similar or more extensive deletions have been previously reported in full. Hypotonia and psychomotor retardation were the only manifestations common to all 6 cases. The phenotype associated with small terminal 2q deletions is variable and clearly not always as mild as indicated in previous reports. The abnormality may also be more common than has been assumed.

Deletion (2)(q37)

We report on a 5-month-old girl with widely spaced nipples, redundant nuchal skin, coarctation of the aorta, anal atresia with distal fistula, postnatal growth retardation, hypotonia, and sparse scalp hair. Initial clinical assessment suggested the diagnosis of Ullrich-Turner syndrome. Chromosome analysis showed a 46,XX,del(2)(q37) karyotype in peripheral lymphocytes. We compare her findings to those of other reported patients with terminal deletions of 2q.

The human vigilin gene: identification, chromosomal localization and expression pattern

Chick vigilin cRNA clones were used to isolate the cognate human gene, by screening a pWE15 genomic library. Three independent cosmid clones were isolated and characterized by restriction mapping. The gene was identified by sequencing an internal EcoRI fragment containing two exons homologous to exon 24 and 25 of the chicken vigilin gene and corresponding to nucleotides 1973-2104 of the human HBP-cDNA. The homology between the chicken and human sequences was 77% and 82% at the cDNA level, and 91% and 100% at the amino acid level. In addition, the analyzed intron/exon boundaries were invariantly conserved. The 5' and 3' regions of the human gene were mapped by Southern analysis of the respective clones with synthetic oligonucleotides. The entire vigilin gene spans a region of about 50 kb and has been assigned to chromosome 2q36-q37.2 (FL-pter value of 0.96 +/- 0.03) by fluorescence in situ hybridization to metaphase spreads from normal peripheral blood lymphocytes. The vigilin gene is localized in a chromosomal region comprising a cluster of collagen genes (COLIVA3, COLVIA3) and the locus of the Waardenburg syndrome I. Only one mRNA species of 4.4 kb is transcribed from the human vigilin gene. In accordance with previous observations on chicken mRNA, the expression of the human vigilin mRNA depends on the stage of cytodifferentiation both in vitro and in situ.

Terminal deletion of the long arm of chromosome 2 in a premature infant with karyotype: 46,XY,del(2)(q37)

We present a premature newborn boy with multiple congenital anomalies, including craniofacial anomalies, syndactyly, cardiac defects, and a horseshoe kidney associated with terminal deletion of 2q. The infant's karyotype was 46,XY,del(2)(q37). Clinical, cytogenetic, and autopsy findings are presented in this report. Clinical manifestations in this infant are compared with those four other known patients with terminal deletion of chromosome 2.

Autopsy findings in a severely affected infant with a 2q terminal deletion

We describe a 37-week gestation female infant who was born with a terminal 2q deletion. Both of her parents had normal chromosomes. This infant had multiple anomalies, including hypertelorism, short palpebral fissures, microphthalmia, cleft lip/cleft palate, and abnormal ears. Autopsy documented Dandy-Walker malformation with severe hydrocephalus, aortopulmonary window, secundum atrial septal defect, duodenal atresia, incomplete rotation of the bowel, gonadal dysgenesis, uterus didelphys, and musculoskeletal defects. Compared with the other 6 children with 2q terminal deletion documented in the literature, this patient is the most severely affected. This patient is also the only one documented to have died and undergone autopsy examination. The findings in this case provide more data for the eventual description of a "terminal 2q deletion syndrome" and suggest that some abnormalities, such as gonadal dysgenesis, may be present in living children with this chromosome abnormality.