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Deletions of the long arm of chromosome 20 (20q) are rare, with only 16 reported patients displaying a proximal interstitial 20q deletion. A 1.62 Mb minimal critical region at 20q11.2, encompassing three genes GDF5, EPB41L1, and SAMHD1, is proposed to be responsible for this syndrome. The leading clinical features include growth retardation, intractable feeding difficulties with gastroesophageal reflux, hypotonia and psychomotor developmental delay. Common facial dysmorphisms including triangular face, hypertelorism, and hypoplastic alae nasi were additionally reported. Here, we present the clinical and molecular findings of five new patients with proximal interstitial 20q deletions. We analyzed the phenotype and molecular data of all previously reported patients with 20q11.2q12 microdeletions, along with our five new cases. Copy number variation analysis of patients in our cohort has enabled us to identify the second critical region in the 20q11.2q12 region and redefine the first region that is initially identified. The first critical region spans 359 kb at 20q11.2, containing six MIM genes, including two disease-causing genes, GDF5 and CEP250. The second critical region spans 706 kb at 20q12, encompassing four MIM genes, including two disease-causing genes, MAFB and TOP1. We propose GDF5 to be the primary candidate gene generating the phenotype of patients with 20q11.2 deletions. Moreover, we hypothesize TOP1 as a potential candidate gene for the second critical region at 20q12. Of note, we cannot exclude the possibility of a synergistic role of other genes involved in the deletion, including a contiguous gene deletion syndrome or position effect affecting both critical regions. Further studies focusing on patients with proximal 20q deletions are required to support our hypothesis., (© 2024 The Authors. American Journal of Medical Genetics Part A published by Wiley Periodicals LLC.)

Background: Since the establishment of chromosomal microarrays in clinical practice, many new microdeletion/microduplication syndromes have been identified, including 18q11.2 microdeletion. Chromosome 18q deletion syndrome is commonly classified into distal deletion and a much rarer proximal interstitial deletion spanning the 18q11.2-q21.1 region., Methods: We report two new patients and review 27 additional cases in DECIPHER/ClinGen databases and four cases from the literature, with more proximal 18q deletions involving 18q11-q12 (band 1 only; 17.2-43.5 Mb position) deletion., Results: Common presentations of 18q11-q12 deletions include developmental delay/intellectual disability (DD/ID) (82%); speech delay/autism/attention deficit and hyperactivity/other behavioral problems (30%); conotruncal heart defects (15%); and subtle/non-specific facial dysmorphism. The deletion in four out of five cases with cardiac defect was distal to GATA6, suggesting an alternative mechanism other than haploinsufficiency of GATA6 as an underlying cause of cardiac malformations. Precocious puberty with advanced skeletal age was first observed in one patient, suggesting a unique and expanded phenotype of proximal 18q deletion. When comparing genotype-phenotype correlations from the present study with previous reports, the critical regions for selected phenotypes of 18q11-q12 deletion syndrome could be narrowed down as follows: 38.8-43.5 Mb for moderate to severe DD/ID, 19.6-24.4 Mb and 26.9-28.6 Mb for conotruncal heart defect., Conclusion: The detailed clinical delineation of the proximal 18q deletions identified in this study should contribute to better understanding of the genotype-phenotype correlations and better long-term care of patients with this rare syndrome., (© 2019 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc.)

Only a few individuals with 12q15 deletion have been described, presenting with a disorder characterized by learning disability, developmental delay, nasal speech, and hypothyroidism. The smallest region of overlap for this syndrome was included in a genomic segment spanning CNOT2, KCNMB4, and PTPRB genes. We report on an additional patient harboring a 12q15 microdeletion encompassing only part of CNOT2 gene, presenting with a spectrum of clinical features overlapping the 12q15 deletion syndrome phenotype. We propose CNOT2 as the phenocritical gene for 12q15 deletion syndrome and its haploinsufficiency being associated with an autosomal dominant disorder, presenting with developmental delay, hypotonia, feeding problems, learning difficulties, nasal speech, skeletal anomalies, and facial dysmorphisms., (© 2019 Wiley Periodicals, Inc.)

Interstitial deletions of the long arm of chromosome 12 are rare and only few cases have been reported in literature so far, with different phenotypic features related to size and gene content of deleted regions. Five patients reported a 12q15-q21 deletion, sharing a 1.3 Mb small region of overlap (SRO) and presenting with developmental delay, nasal speech and mild dysmorphic features. We identified by microarray analysis a new case of 12q15 deletion. Our patient clinical features allow the refinement of the SRO to CNOT2, KCNMB4, and PTPRB genes, improving genotype-phenotype correlations., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Background: The Dandy-Walker malformation (DWM) is one of the commonest congenital cerebellar defects, and can be associated with multiple congenital anomalies and chromosomal syndromes. The occurrence of overlapping 3q deletions including the ZIC1 and ZIC4 genes in few patients, along with data from mouse models, have implicated both genes in the pathogenesis of DWM., Methods and Results: Using a SNP-array approach, we recently identified three novel patients carrying heterozygous 3q deletions encompassing ZIC1 and ZIC4. Magnetic resonance imaging showed that only two had a typical DWM, while the third did not present any defect of the DWM spectrum. SNP-array analysis in further eleven children diagnosed with DWM failed to identify deletions of ZIC1-ZIC4. The clinical phenotype of the three 3q deleted patients included multiple congenital anomalies and peculiar facial appearance, related to the localization and extension of each deletion. In particular, phenotypes resulted from the variable combination of three recognizable patterns: DWM (with incomplete penetrance); blepharophimosis, ptosis, and epicanthus inversus syndrome; and Wisconsin syndrome (WS), recently mapped to 3q., Conclusions: Our data indicate that the 3q deletion is a rare defect associated with DWM, and suggest that the hemizygosity of ZIC1-ZIC4 genes is neither necessary nor sufficient per se to cause this condition. Furthermore, based on a detailed comparison of clinical features and molecular data from 3q deleted patients, we propose clinical diagnostic criteria and refine the critical region for WS.

Turner syndrome is a condition caused by numeric and structural abnormalities of the X chromosome, and is characterized by a series of clinical features, the most common being short stature and gonadal dysgenesis. An increased frequency of autoimmune diseases as well as an elevated incidence of autoantibodies has been observed in Turner patients. We present a unique case of mosaic Turner syndrome with a complex rearrangement consisting of a partial deletion of chromosome 2q and duplication of chromosome 10p {[46],XX,der(2)t(2;10)(2pter→2q37::10p13→10pter)[127]/45,X,der(2)t(2;10)(2pter→2q37::10p13→10pter)[23]}. The patient is affected by partial empty sella, in association with a group of multiorgan autoimmunity-related manifestations including Hashimoto's thyroiditis, celiac disease, insulin-dependent diabetes mellitus (Type 1 diabetes, T1D), possible autoimmune inner ear disease with sensorineural deficit, preclinical Addison disease and alopecia universalis. The patient was previously described at the age of 2.4 years and now re-evaluated at the age of 14 years after she developed autoimmune conditions. AIRE gene screening revealed heterozygous c.834 C>G polymorphism (p.Ser278Arg) and IVS9+6G>A variation, thus likely excluding autoimmune polyendocrine syndrome Type 1 (APECED). Heterozygous R620W polymorphism of the protein tyrosine phosphatase non receptor type 22 (PTPN22) gene was detected in patient's DNA. SNP-array analysis revealed that autoimmunity-related genes could be affected by the partial monosomy 2q and trisomy 10p. These data suggest that early genetic analysis in TS patients with complex associations of multiorgan autoimmune manifestations would permit a precise diagnostic classification and also be an indicator for undiscovered pathogenetic mechanisms., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Two 1p36 contiguous gene deletion syndromes are known so far: the terminal 1p36 deletion syndrome and a 1p36 deletion syndrome with a critical region located more proximal at 1p36.23‐1p36.22. We present even more proximally located overlapping deletions from seven individuals, with the smallest region of overlap comprising 1 Mb at 1p36.13‐1p36.12 (chr1:19077793‐20081292 (GRCh37/hg19)) defining a new contiguous gene deletion syndrome. The characteristic features of this new syndrome are learning disability or mild intellectual disability, speech delay, behavioral abnormalities, and ptosis. The genes UBR4 and CAPZB are considered the most likely candidate genes for the features of this new syndrome. [ABSTRACT FROM AUTHOR]