Two patients with chromosome 6q terminal deletions with breakpoints at q24.3 and q25.3

We report on 2 patients with de novo terminal deletion of 6q. The first was a 4-month-old boy whose karyotype was 46, XY, del(6)(q24.3); the second a 2-year-old girl whose karyotype was 46, XX, del(6)(q25.3). The main anomalies in both patients included mental retardation, minor craniofacial and cerebral anomalies, and cardiac defects. The characteristic manifestations were imperforate anus in the first patient, and retinitis proliferans and a triatrial heart in the other. Comparison of clinical findings of our 2 patients with those of 18 previously reported patients with similar phenotypes suggests that terminal deletion of the 6q23 or 6q25 band is critical in producing the main anomalies of del(6q) syndrome. © 1992 Wiley-Liss, Inc.     

Two patients with chromosome 6q terminal deletions with breakpoints at q24.3 and q25.3.

We report on 2 patients with de novo terminal deletion of 6q. The first was a 4-month-old boy whose karyotype was 46,XY,del(6)(q24.3); the second a 2-year-old girl whose karyotype was 46, XX, del(6)(q25.3). The main anomalies in both patients included mental retardation, minor craniofacial and cerebral anomalies, and cardiac defects. The characteristic manifestations were imperforate anus in the first patient, and retinitis proliferans and a triatrial heart in the other. Comparison of clinical findings of our 2 patients with those of 18 previously reported patients with similar phenotypes suggests that terminal deletion of the 6q23 or 6q25 band is critical in producing the main anomalies of del(6q) syndrome.     

Clinical phenotype and molecular characterization of 6q terminal deletion syndrome: Five new cases

Mental retardation, facial dysmorphisms, seizures, and brain abnormalities are features of 6q terminal deletions. We have ascertained five patients with 6q subtelomere deletions (four de novo, one as a result of an unbalanced translocation) and determined the size of the deletion ranging from 3 to 13 Mb. Our patients showed a recognizable phenotype including mental retardation, characteristic facial appearance, and a distinctive clinico-neuroradiological picture. Focal epilepsy with consistent electroencephalographic features and with certain brain anomalies on neuroimaging studies should suggest 6q terminal deletion. The awareness of the distinctive clinical picture will help in the diagnosis of this chromosomal abnormality.     

An emerging phenotype of proximal 11q deletions

Few reports of small interstitial chromosome 11q deletions are reported in the literature and no clear genotype–phenotype correlation has been demonstrated.We describe a five years old boy who was referred to our attention because of the presence of ptosis of the left eyelid, iris coloboma and developmental delay.Clinical examination also revealed the presence of dysmorphic features including: low frontal hairline, flat profile, round face, full cheeks, periorbital fullness, hypertelorism, broad nasal bridge, down-turned corners of the mouth.Cytogenetic analysis, performed by array-CGH (resolution 1 Mb), revealed a deletion of chromosome 11q13.5q14.2.The present case represents a further patient described in the literature with a small interstitial deletion of chromosome 11q. Our patient shares the dysmorphic features and the presence of developmental delay with the previously reported patients with overlapping proximal 11q deletion.Considering these clinical and cytogenetic similarities, we suggest the existence of an emerging syndrome associated to proximal 11q deletions.     

A phenotype map for 14q32.3 terminal deletions

Detailed molecular-cytogenetic studies combined with thorough clinical characterization are needed to establish genotype-phenotype correlations for specific chromosome deletion syndromes. Although many patients with subtelomeric deletions have been reported, the phenotype maps for many of the corresponding syndromes, including the terminal deletion 14q syndrome, are only slowly emerging. Here, we report on five patients with terminal partial monosomy of 14q32.3 and characteristic features of terminal deletion 14q syndrome. Four of the patients carry de novo terminal deletions of 14q, three of which have not yet been reported. One patient carries an unbalanced translocation der(14)t(9;14)(q34.3;q32.3). Minimum deletion sizes as determined by molecular karyotyping and FISH are 5.82, 5.56, 4.17, 3.54, and 3.29?Mb, respectively. Based on our findings and a comprehensive review of the literature, we refine the phenotype map for typical clinical findings of the terminal deletion 14q syndrome (i.e., intellectual disability/developmental delay, muscular hypotonia, postnatal growth retardation, microcephaly, congenital heart defects, genitourinary malformations, ocular coloboma, and several dysmorphic signs). Combining this phenotype map with benign copy-number variation data available from the Database of Genomic Variants, we propose a small region critical for certain features of the terminal deletion 14q syndrome which contains only seven RefSeq genes.     

Recurrent interstitial deletions of proximal 18q: a new syndrome involving expressive speech delay

Most deletions of the long arm of chromosome 18 involve some part of the most distal 30 Mb. We have identified five individuals with cytogenetically diagnosed interstitial deletions that are all proximal to this commonly deleted region. The extent of their deletions was characterized using molecular and molecular cytogenetic techniques. Each participant was assessed under the comprehensive clinical evaluation protocol of the Chromosome 18 Clinical Research Center. Three of the five individuals were found to have apparently identical interstitial deletions between positions of 37.5 and 42.5 Mb (18q12.3-->18q21.1). One individual's deletion was much larger and extended from a more proximal breakpoint position of 23 Mb (18q11.2) to a more distal breakpoint at 43 Mb (18q21.1). The fifth individual had a proximal breakpoint identical to the other three, but a distal breakpoint at 43.5 Mb (18q21.1). The clinical findings were of interest because the three individuals with the smaller deletions lacked major anomalies. All five individuals were developmentally delayed; however, the discrepancy between their expressive and receptive language abilities was striking, with expressive language being much more severely affected. This leads us to hypothesize that there are genes in this region of chromosome 18 that are specific to the neural and motor planning domains necessary for speech. Additionally, this may represent a previously underappreciated syndrome since these children do not have the typical clinical abnormalities that would lead to a chromosome analysis.     

Patient with terminal duplication 3q and terminal deletion 5q: comparison with the 3q duplication syndrome and distal 5q deletion syndrome

Partial duplication of chromosome 3q is a well-described condition of multiple congenital anomalies and developmental delay that resembles the Brachmann-de Lange syndrome. Similarly, an emerging phenotype of a distal 5q deletion syndrome has recently been described. The combination of both chromosome abnormalities has not been previously described. We report on a child with both a de novo duplication of distal 3q (q27 --> qter) and terminal deletion of 5q (q35.2 --> qter). The patient had facial anomalies, hypoplastic toenails, lymphedema of the dorsum of the feet, type I Chiari malformation, a seizure disorder, and moderate developmental delays. The phenotype is compared and contrasted to the few reports of patients with similar terminal 3q duplications and 5q deletions. Our patient did not have the characteristic phenotype of the 3q duplication syndrome, suggesting that the chromosome region responsible for this phenotype is more proximal than the terminal 3q27 region. In addition, comparison with three other reported cases of terminal 5q35 deletions suggests a possible association of terminal 5q deletions with central nervous system (CNS) structural abnormalities.     

Subtle overlapping deletions in the terminal region of chromosome 6q24.2-q26: Three cases studied using FISH

Interstitial deletions in the terminal region of chromosome 6 are rare. We describe three new cases with subtle interstitial deletions in the q24-q26 region of the long arm of chromosome 6. The karyotypes were analyzed at a 550 band level. Patient1 is a 9-month-old boy with an interstitial deletion, del(6)(q24.2q25.1), developmental delay, low birth weight, hypotonia, heart murmur, respiratory distress, craniofacial and genital anomalies. This is the first report of a case with deletion del(6)(q24.2q25.1). Patient 2 is a 17-year-old young man with an interstitial deletion del(6)(q25.1q25.3), developmental delay, short stature, mental retardation, autism, head, face, chest, hand and feet anomalies and a history of seizures. For the first time autism was described as a manifestation in 6q deletions. Patient 3 is baby boy with a de novo interstitial deletion, del(6)(q25.1q26), anomalies of the brain, genital organs, limbs and feet. This is the first report of a case with deletion, del(6)(q25.1q26). In all three patients, fluorescence in situ hybridization (FISH) using chromosome 6 painting probe ruled out an insertion. The ESR (6q25.1) and TBP (6q27) probes were used to confirm the breakpoints. Since TBP signal is present in all cases, it confirmed an interstitial deletion proximal to this probe. Patient 1 has a deletion of the ESR locus; Patient 2 and 3 have signals for the ESR locus on both chromosomes 6. Therefore the deletion in Patients 2 and 3 are between ESR and TBP loci distal to that of Patient 1. FISH validated the deletion breakpoints assessed by conventional cytogenetics. Am. J. Med. Genet. 87:17–22, 1999. © 1999 Wiley-Liss, Inc.     

Wilms tumor incidence in children with 2q terminal deletions: a cohort study

Three individuals with chromosome 2q terminal deletions have been reported in the medical literature to have developed Wilms tumor. By looking at a UK national cohort, we aimed to ascertain the chance of an individual with a 2q terminal deletion developing a Wilms tumor. The objective was to clarify screening recommendations. All individuals over a 40-year period with chromosome 2q terminal deletions were ascertained from the Chromosome Abnormality Database. The names and dates of birth of these individuals were obtained from the Regional Cytogenetic Departments where the original chromosome analyses were performed. These data were collated and compared with the National Registry of Childhood Tumors. One hundred twenty-nine subjects were identified over a 40-year study period. Only a single individual in our national cohort was affected by Wilms tumor. This individual had an add(2)(q35) karyotype. We conclude that the incidence of Wilms tumor in the majority of individuals with a 2q terminal deletion is low, and is below the recommended threshold for surveillance for tumor development.     

Analysis of clinical variation seen in patients with 18q terminal deletions

Twenty-six patients with deletions of 18q were analyzed at the clinical and molecular levels in an attempt to delineate regions of chromosome 18 important to the 18q– syndrome phenotype. Molecular cytogenetic analysis was carried out using fluorescence in situ hybridization (FISH), and deletions ranging from 18q21.1–qter to 18q22.3–qter were detected. The parental origin of the deletions was determined by the analysis of inheritance of microsatellite markers. No correlation between size, parental origin, or severity of the resulting phenotype was found. The results suggest that a critical region for the 18q– syndrome lies in the most distal portion of 18q and that it confers susceptibility for the various clinical manifestations of the 18q– syndrome when present in one copy. © 1995 Wiley-Liss, Inc.     

New insights into the phenotypes of 6q deletions

Deletions of chromosome 6q are rare. We report 3 new patients with 6q deletions. Case 1 is a male with an interstitial deletion [del(6)(q13q14.2)], hypotonia, speech delays, and minor anomalies. Case 2 is a male with an interstitial deletion [del(6)(q16.2q22.32)] and malformations, including truncus arteriosus and bilateral oligodactyly. Case 3 is a male with a terminal deletion [del(6)(q25.2)] with retinal pits, hydrocephalus, atrioventricular canal, and hydronephrosis. The findings in our patients and those from 57 previously reported cases demonstrated 3 phenotypic groups associated with 6q deletions. Group A [del(6)(q11–q16)] had a high incidence of hernias, upslanting palpebral fissures, and thin lips with lower frequency of microcephaly, micrognathia, and heart malformations. Group B [del(6)(q15–q25)] was associated with increased intrauterine growth retardation, abnormal respiration, hypertelorism, and upper limb malformations. Group C [del(6)(q25-qter)] was associated with retinal abnormalities, cleft palate, and genital hypoplasia. The only universal finding among all patients with 6q deletions was mental retardation. Other findings common to all 3 groups included ear anomalies (90%), hypotonia (82%), and postnatal growth retardation (68%). Am. J. Med. Genet. 70:377–386, 1997. © 1997 Wiley-Liss, Inc.     

Velo-cardio-facial syndrome: Frequency and extent of 22q1l deletions

Velo-cardio-facial. (VCFS) or Shprintzen syndrome is associated with deletions in a region of chromosome 22q11.2 also deleted in DiGeorge anomaly and some forms of congenital heart disease. Due to the variability of phonotype, the evaluation of the incidence of deletions has been hampered by uncertainty of diagnosis. In this study, 54 patients were diagnosed with VCFS by a single group of clinicians using homogeneous clinical criteria independent of the deletion status. Cell lines of these patients were established and the deletion status evaluated for three loci within the commonly deleted region at 22q11.2 using fluorescence in situ hybridization (FISH). In 81% of the patients all three loci were hemizygous. In one patient we observed a smaller interstitial deletion than that defined by the three loci. The phenotype of this patient was not different from that observed in patients with larger deletions. © 1995 Wiley-Liss, Inc.     

Interstitial deletions of chromosome 6q: genotype-phenotype correlation utilizing array CGH

Interstitial deletions of the long arm of chromosome 6 are relatively rare, with fewer than 100 cases reported. Phenotypic variation is in large part due to differences in size and location of the segmental aneuploidy. We report three new patients with interstitial deletions of chromosome 6q defined at the molecular level by array comparative genomic hybridization (array CGH). In two of three cases, the molecular breakpoints differed from those indicated by conventional karyotyping, demonstrating the enhanced resolution of array CGH. Two patients had minimal deletions of 6 and 8.8 Mb involving 6q16.2-->q21, and the third patient had a deletion of 11.3 Mb spanning 6q15-->q21. All three had developmental delay, craniofacial dysmorphology, and functional eye disorders, suggesting that genes affecting brain and craniofacial development are located in 6q16.2-->q21, the deleted region common to all three patients. Furthermore, gene(s) for discordant phenotypic features, such as central diabetes insipidus, may reside at 6q15, the monosomic region unique to patient 3. All three cases described here showed loss of paternal alleles within the deleted segment, providing further evidence of the predominantly paternal origin for 6q deletions and rearrangements.     

Delineation of candidate genes responsible for structural brain abnormalities in patients with terminal deletions of chromosome 6q27

Patients with terminal deletions of chromosome 6q present with structural brain abnormalities including agenesis of corpus callosum, hydrocephalus, periventricular nodular heterotopia, and cerebellar malformations. The 6q27 region harbors genes that are important for the normal development of brain and delineation of a critical deletion region for structural brain abnormalities may lead to a better genotype–phenotype correlation. We conducted a detailed clinical and molecular characterization of seven unrelated patients with deletions involving chromosome 6q27. All patients had structural brain abnormalities. Using array comparative genomic hybridization, we mapped the size, extent, and genomic content of these deletions. The smallest region of overlap spans 1.7 Mb and contains DLL1, THBS2, PHF10, and C6orf70 (ERMARD) that are plausible candidates for the causation of structural brain abnormalities. Our study reiterates the importance of 6q27 region in normal development of brain and helps identify putative genes in causation of structural brain anomalies.     

Three patients with terminal deletions within the subtelomeric region of chromosome 9q

We report on three male infants with de novo terminal deletions of chromosome 9q34.3. The clinical features are compared to the nine cases described in the literature. Case 1 and 3 were ascertained following the use of subtelomeric FISH to screen for a chromosomal anomaly, case 2 was confirmed by FISH probe following detection of a 9q deletion on standard karyotyping. Deletions in this region result in severe developmental delay, a distinct facial phenotype, cardiac anomalies, obesity, and respiratory failure, which may result in premature death. The delineation of the 9q deletion phenotype will aid diagnosis and genetic counseling as subtelomere FISH screening becomes more widely available.     

Clinical and molecular characterization of an emerging chromosome 22q13.31 microdeletion syndrome

Microdeletion of chromosome 22q13.31 is a very rare condition. Fourteen patients have been annotated in public databases but, to date, a clinical comparison has not been done and, consequently, a specific phenotype has not been delineated yet. We describe a patient showing neurodevelopmental disorders, dysmorphic features, and multiple congenital anomalies in which SNP array analysis revealed an interstitial 3.15 Mb de novo microdeletion in the 22q13.31 region encompassing 21 RefSeq genes and seven non‐coding microRNAs. To perform an accurate phenotype characterization, clinical features observed in previously reported cases of 22q13.31 microdeletions were reviewed and compared to those observed in our patient. To the best of our knowledge, this is the first time that a comparison between patients carrying overlapping 22q13.31 deletions has been done. This comparison allowed us to identify a distinct spectrum of clinical manifestations suggesting that patients with a de novo interstitial microdeletion involving 22q13.31 have an emerging syndrome characterized by developmental delay/intellectual disability, speech delay/language disorders, behavioral problems, hypotonia, urogenital, and hands/feet anomalies. The microdeletion identified in our patient is the smallest reported so far and, for this reason, useful to perform a detailed genotype‐phenotype correlation. In particular, we propose the CELSR1, ATXN10, FBLN1, and UPK3A as candidate genes in the onset of the main clinical features of this contiguous gene syndrome. Thus, the patient reported here broadens our knowledge of the phenotypic consequences of 22q13.31 microdeletions facilitating genotype‐phenotype correlations. Additional cases are needed to corroborate our hypothesis and confirm genotype–phenotype correlations of this emerging syndrome.