Identification of two novel heterozygous variants of SMC3 with Cornelia de Lange syndrome.

BACKGROUND: Cornelia de Lange syndrome (CdLS) is a multisystem genetic disorder, and cases caused by variants in the structural maintenance of chromosomes protein 3 (SMC3) gene are uncommon. Here, we report two cases of CdLS associated with novel pathogenic variants in SMC3 from two Chinese families. METHODS: Clinical presentations of two patients with CdLS were evaluated, and specimens from the patients and other family members were collected for Trio-based whole-exome sequencing. Pyrosequencing, chip-based digital PCR, minigene splicing assay, and in silico analysis were carried out to elucidate the impact of novel variants. RESULTS: Novel heterozygous variants in SMC3 were identified in each proband. One harbored a novel splicing and mosaic variant (c.2535+1G>A) in SMC3. The mutated allele G>A conversion was approximately 23.1% by digital PCR, which indicated that 46.2% of peripheral blood cells had this variant. Additionally, in vitro minigene splicing analysis validated that the c.2535+1G>A variant led to an exon skipping in messenger RNA splicing. The other carried a heterozygous variant (c.435C>A), which was predicted to be pathogenic as well as significantly altered in local electrical potential. The former showed multiple abnormalities and marked clinical severity, and the latter mainly exhibited a speech developmental disorder and slightly facial anomalies. CONCLUSION: Both patients were clinically diagnosed with Cornelia de Lange syndrome 3 (CdLS3). The newly identified SMC3 gene variants can expand the understanding of CdLS3 and provide reliable evidence for genetic counseling to the affected family.

Mutation profiling in South African patients with Cornelia de Lange syndrome phenotype.

BACKGROUND: Cornelia de Lange Syndrome (CdLS) presents with a variable multi-systemic phenotype and pathogenic variants have been identified in five main genes. This condition has been understudied in African populations with little phenotypic and molecular information available. METHODS AND RESULTS: We present a cohort of 14 patients with clinical features suggestive of CdLS. Clinical phenotyping was carried out and cases were classified according to the international consensus criteria. According to this criteria, nine patients had classical CdLS, one had non-classical CdLS and four presented with a phenotype that suggested molecular testing for CdLS. Each patient underwent mutation profiling using a targeted next generation sequencing panel of 18 genes comprising known and suspected CdLS causal genes. Of the 14 patients tested, pathogenic and likely pathogenic variants were identified in nine: eight variants in the NIPBL gene and one in the STAG1 gene. CONCLUSIONS: We present the first molecular data for a cohort of South African patients with CdLS. Eight of the nine variants identified were in the NIPBL gene, the most commonly involved gene in cases of CdLS. This is also the first report of a patient of African ancestry presenting with STAG1-related CdLS.

Novel PUF60 variant suggesting an interaction between Verheij and Cornelia de Lange syndrome: phenotype description and review of the literature.

Verheij syndrome [VRJS; OMIM 615583] is a rare autosomal dominant neurodevelopmental disorder characterized by distinct clinical features, including growth retardation, intellectual disability, cardiac, and renal anomalies. VRJS is caused by deletions of chromosome 8q24.3 or pathogenic variants in the PUF60 gene. Recently, pathogenic PUF60 variants have been reported in some individuals with VRJS, contributing to the variability in the clinical presentation and severity of the condition. PUF60 encodes a protein involved in regulating gene expression and cellular growth. In this report, we describe a new case of VRJS with developmental delay, cardiac-, and renal abnormalities, caused by a heterozygous pathogenic PUF60 variant. Surprisingly, DNA methylation analysis revealed a pattern resembling the Cornelia de Lange syndrome (CdLS) episignature, suggesting a potential connection between PUF60 and CdLS-related genes. This case report further delineates the clinical and molecular spectrum of VRJS and supports further research to validate the interaction between VRJS and CdLS.

Cornelia de Lange Syndrome Caused by an Intragenic Heterozygous Deletion in RAD21 Detected through Very-High-Resolution Chromosomal Microarray Analysis.

Cornelia de Lange syndrome is a genetic and clinically heterogeneous entity, caused by at least five genes. It is characterized by short stature, gestalt facies, microcephaly, neurodevelopmental disorders, and other anomalies. In this report, we present a 13-year-old female patient with microcephaly, cleft palate, polydactyly, short stature, triangular facies, frontal bossing, a bulbous nose, an overfolded helix, limited pronosupination, and an anomalous uterus. No neurodevelopmental disorders were reported. A chromosomal microarray analysis of 6.5 million markers was performed in the proband and her parents. The results showed a de novo heterozygous microdeletion of exons 9-14 within RAD21, which confirmed the diagnosis of Cornelia de Lange syndrome type 4. Our patient did not show any neurologic phenotype (until the time of diagnosis), although neurodevelopmental disorders are frequently present in patients with Cornelia de Lange syndrome type 4, and despite carrying a deletion that was larger than previously reported. Therefore, unknown genetic modifiers or intrinsic mechanisms of RAD21 variants may exist and should be studied.

Manejo odontológico en paciente con síndrome de Cornelia de Lange / Dental treatment of a patient with Cornelia de Lange syndrome

El síndrome de Cornelia de Lange (SCdL) es un trastorno genético poco frecuente y se atribuye principalmente a mutaciones en los genes NIPBL, SMC3 y SMC1A. Sus principales características clínicas son múltiples anomalías congénitas, dimorfismo facial, hirsutismo, hipertricosis, retraso psicomotor, discapacidad intelectual, restricción del crecimiento prenatal y postnatal, anomalías de manos y pies, así como malformaciones congénitas que afectan a distintos órganos. En pacientes con SCdL es necesario hacer hincapié en la higiene oral debido a la discapacidad intelectual que puede presentarse y asegurarse de que se realiza una adecuada valoración y saneamiento dental de forma periódica con el fin de prevenir enfermedades bucodentales. El objetivo de este reporte de caso es describir el manejo odontológico de un paciente de 10 años con SCdL y revisar las características clínicas y hallazgos radiológicos presentes en la cavidad oral (AU)

Cornelia de Lange syndrome (CdLS) is a rare genetic disorder and is principally attributed to mutations in the NIPBL, SMC3 and SMC1A genes. The main clinical characteristics are multiple congenital anomalies, facial dimorphism, hirsutism, hypertrichosis, psychomotor retardation, intellectual disability, prenatal and postnatal growth restriction, hand and foot anomalies, as well as congenital malformations affecting different organs. In patients with CDLS, it is necessary to focus on oral hygiene due to the intellectual disability that may be present and to ensure that adequate dental valuation and hygiene is routinely performed in order to prevent oral diseases. The aim of this case report is to describe the dental management of a 10-year-old patient with CDLS and review the clinical characteristics and radiological findings that are present in the oral cavity (AU)

Genomic analyses in Cornelia de Lange Syndrome and related diagnoses: Novel candidate genes, genotype-phenotype correlations and common mechanisms.

Cornelia de Lange Syndrome (CdLS) is a rare, dominantly inherited multisystem developmental disorder characterized by highly variable manifestations of growth and developmental delays, upper limb involvement, hypertrichosis, cardiac, gastrointestinal, craniofacial, and other systemic features. Pathogenic variants in genes encoding cohesin complex structural subunits and regulatory proteins (NIPBL, SMC1A, SMC3, HDAC8, and RAD21) are the major pathogenic contributors to CdLS. Heterozygous or hemizygous variants in the genes encoding these five proteins have been found to be contributory to CdLS, with variants in NIPBL accounting for the majority (>60%) of cases, and the only gene identified to date that results in the severe or classic form of CdLS when mutated. Pathogenic variants in cohesin genes other than NIPBL tend to result in a less severe phenotype. Causative variants in additional genes, such as ANKRD11, EP300, AFF4, TAF1, and BRD4, can cause a CdLS-like phenotype. The common role that these genes, and others, play as critical regulators of developmental transcriptional control has led to the conditions they cause being referred to as disorders of transcriptional regulation (or "DTRs"). Here, we report the results of a comprehensive molecular analysis in a cohort of 716 probands with typical and atypical CdLS in order to delineate the genetic contribution of causative variants in cohesin complex genes as well as novel candidate genes, genotype-phenotype correlations, and the utility of genome sequencing in understanding the mutational landscape in this population.

Chung-Jansen syndrome can mimic Cornelia de Lange syndrome: Another player among chromatinopathies?

Cornelia de Lange syndrome (CdLS) is a rare multisystem congenital neurodevelopmental disorder (NDD) characterized by distinctive facial anomalies, short stature, developmental delay, hirsutism, gastrointestinal abnormalities and upper limb reduction defects. CdLS syndrome is associated with causative variants in genes encoding for the cohesin complex, a cellular machinery involved in chromatid pairing, DNA repair and gene-expression regulation. In this report, we describe a familial case of a syndromic presentation in a 4-year-old patient (P1) and in his mother (P2). Trio-based Whole Exome Sequencing (WES) performed on P1 was first negative. Since his phenotypic evolution during the follow-up was reminiscent of the CdLS spectrum, a reanalysis of WES data, focused on CdLS-related genes, was requested. Although no alterations in those genes was detected, we identified the likely pathogenetic variant c.40G > A (p.Glu14Lys) in the PHIP gene, in the meanwhile associated with Chung-Jansen syndrome. Reverse phenotyping carried out in both patients confirmed the molecular diagnosis. CHUJANS belongs to NDDs, featuring developmental delay, mild-to-moderate intellectual disability, behavioral problems, obesity and facial dysmorphisms. Moreover, as here described, CHUJANS shows a significant overlap with the CdLS spectrum, with specific regard to facial gestalt. On the basis of our findings, we suggest to include PHIP among genes routinely analyzed in patients belonging to the CdLS spectrum.

Pathogenic variants detected by RNA sequencing in Cornelia de Lange syndrome.

Recent studies suggest that transcript isoforms significantly overlap (approximately 60%) between brain tissue and Epstein-Barr virus-transformed lymphoblastoid cell lines (LCLs). Interestingly, 14 cohesion-related genes with variants that cause Cornelia de Lange Syndrome (CdLS) are highly expressed in the brain and LCLs. In this context, we first performed RNA sequencing of LCLs from 22 solved (with pathogenic variants) and 19 unsolved (with no confirmed variants) CdLS cases. Next, an RNA sequencing pipeline was developed using solved cases with two different methods: short variant analysis (for single-nucleotide and indel variants) and aberrant splicing detection analysis. Then, 19 unsolved cases were subsequently applied to our pipeline, and four pathogenic variants in NIPBL (one inframe deletion and three intronic variants) were newly identified. Two of three intronic variants were located at Alu elements in deep-intronic regions, creating cryptic exons. RNA sequencing with LCLs was useful for identifying hidden variants in exome-negative cases.

A Novel Intragenic Duplication in the HDAC8 Gene Underlying a Case of Cornelia de Lange Syndrome.

Cornelia de Lange syndrome (CdLS) is a multisystemic genetic disorder characterized by distinctive facial features, growth retardation, and intellectual disability, as well as various systemic conditions. It is caused by genetic variants in genes related to the cohesin complex. Single-nucleotide variations are the best-known genetic cause of CdLS; however, copy number variants (CNVs) clearly underlie a substantial proportion of cases of the syndrome. The NIPBL gene was thought to be the locus within which clinically relevant CNVs contributed to CdLS. However, in the last few years, pathogenic CNVs have been identified in other genes such as HDAC8, RAD21, and SMC1A. Here, we studied an affected girl presenting with a classic CdLS phenotype heterozygous for a de novo ~32 kbp intragenic duplication affecting exon 10 of HDAC8. Molecular analyses revealed an alteration in the physiological splicing that included a 96 bp insertion between exons 9 and 10 of the main transcript of HDAC8. The aberrant transcript was predicted to generate a truncated protein whose accessibility to the active center was restricted, showing reduced ease of substrate entry into the mutated enzyme. Lastly, we conclude that the duplication is responsible for the patient's phenotype, highlighting the contribution of CNVs as a molecular cause underlying CdLS.

Deep intronic NIPBL de novo mutations and differential diagnoses revealed by whole genome and RNA sequencing in Cornelia de Lange syndrome patients.

Cornelia de Lange syndrome (CdLS; MIM# 122470) is a rare developmental disorder. Pathogenic variants in 5 genes explain approximately 50% cases, leaving the other 50% unsolved. We performed whole genome sequencing (WGS) ± RNA sequencing (RNA-seq) in 5 unsolved trios fulfilling the following criteria: (i) clinical diagnosis of classic CdLS, (ii) negative gene panel sequencing from blood and saliva-isolated DNA, (iii) unaffected parents' DNA samples available and (iv) proband's blood-isolated RNA available. A pathogenic de novo mutation (DNM) was observed in a CdLS differential diagnosis gene in 3/5 patients, namely POU3F3, SPEN, and TAF1. In the other two, we identified two distinct deep intronic DNM in NIPBL predicted to create a novel splice site. RT-PCRs and RNA-Seq showed aberrant transcripts leading to the creation of a novel frameshift exon. Our findings suggest the relevance of WGS in unsolved suspected CdLS cases and that deep intronic variants may account for a proportion of them.

A Novel de Novo Variant in 5' UTR of the NIPBL Associated with Cornelia de Lange Syndrome.

Background: Cornelia de Lange syndrome (CdLS) is a genetic syndrome characterized by intellectual disability, special facial features, growth retardation, feeding difficulties, and multiple organ system abnormalities. NIPBL variants occur in approximately 80% of CdLS cases. Aims: We report a novel de novo heterozygous pathogenic variant in the NIPBL and its association with CdLS. We also examined the key regulatory sequences of the 5' untranslated region in NIPBL mRNA. Few studies have reported mutation sites in the 5' untranslated region (UTR) of the NIPBL that result in CdLS. Methods: The patient's medical history, clinical manifestations, physical examination, laboratory examination, Griffiths development assessment scale­Chinese version, and cardiac B-ultrasound were examined. Mutation screening was conducted using trio whole exome sequencing (trio-WES) and Sanger sequencing. Quantitative PCR was performed to measure the NIPBL expression in peripheral blood mononuclear cells. A Dual-Luciferase reporter assay was conducted to evaluate the transcription of truncated mutants. Results: The proband showed characteristics of CdLS including thick eyebrows, a concave nasal ridge, long and smooth philtrum, downturned corners of the mouth, intellectual disability, postnatal growth retardation, and a short fifth toe. A novel de novo heterozygous pathogenic variant in the NIPBL (c.-467C > T) was identified. A Dual-Luciferase reporter gene assay showed that SPO1 (-490 bp to -360 bp) and SPO3 (-490 bp to -401 bp) induced the highest activity. Conclusions: We found a novel de novo heterozygous pathogenic variant (c.-467C > T) in the NIPBL resulting in CdLS. Our findings expand the spectrum of pathogenic mutations for CdLS. Our in vitro experiments elucidated important regulatory sequences in the 5' UTR of the NIPBL.

Understanding the new BRD4-related syndrome: Clinical and genomic delineation with an international cohort study.

BRD4 is part of a multiprotein complex involved in loading the cohesin complex onto DNA, a fundamental process required for cohesin-mediated loop extrusion and formation of Topologically Associating Domains. Pathogenic variations in this complex have been associated with a growing number of syndromes, collectively known as cohesinopathies, the most classic being Cornelia de Lange syndrome. However, no cohort study has been conducted to delineate the clinical and molecular spectrum of BRD4-related disorder. We formed an international collaborative study, and collected 14 new patients, including two fetuses. We performed phenotype and genotype analysis, integrated prenatal findings from fetopathological examinations, phenotypes of pediatric patients and adults. We report the first cohort of patients with BRD4-related disorder and delineate the dysmorphic features at different ages. This work extends the phenotypic spectrum of cohesinopathies and characterize a new clinically relevant and recognizable pattern, distinguishable from the other cohesinopathies.

A Chinese Case of Cornelia de Lange Syndrome Caused by a Pathogenic Variant in SMC3 and a Literature Review.

Purpose: Cornelia de Lange syndrome (CdLS) is a rare congenital developmental disorder, and cases caused by variants in SMC3 are infrequent. This article describes a case of CdLS related to a pathogenic variant in SMC3 and performs a literature review. Methods: We collected clinical data and biological samples from a 12-year-old boy with "short stature for 11 years". Gene variants in the proband were detected by whole-exome sequencing, and the variants in his parents were verified by Sanger sequencing. All SMC3-related CdLS patients from the PubMed and Web of Science databases were collected and summarized using the available data. Results: A pathogenic variant in SMC3 in the proband, c.1942A>G, was identified. Neither of his parents carried the same variant. Twenty-eight patients were diagnosed with CdLS with variants in SMC3, including the cases in this study and those reported in the literature, where half of the variant types were missense, followed by 32% (9/28) with a deletion and 11% (3/28) with a duplication. All patients showed symptoms of verbal development delay and intellectual disability to different degrees, and 90% patients had long eyelashes while 89% patients had arched eyebrows. Conclusion: This study summarized different gene variants in SMC3 and the frequencies of the various clinical manifestations according to the reported literature. For CdLS caused by SMC3 variants, short stature and facial dysmorphic features are the two most important clinical clues. Definite diagnosis of this rare disease may be challenging clinically; thus, it is significant to use molecular diagnosis.

A novel de novo HDAC8 missense mutation causing Cornelia de Lange syndrome.

BACKGROUND: Cornelia de Lange syndrome (CdLS) is a rare and clinically variable syndrome characterized by growth impairment, multi-organ anomalies, and a typical set of facial dysmorphisms. Here we describe a 2-year-old female child harboring a novel de novo missense variant in HDAC8, whose phenotypical score, according to the recent consensus on CdLS clinical diagnostic criteria, allowed the diagnosis of a non-classic CdLS. METHODS: Clinical exome sequencing was performed on the trio, identifying a de novo heterozygous variant in HDAC8 (NM_018486; c. 356C>G p.Thr119Arg). Molecular modeling was performed to evaluate putative functional consequence of the HDAC8 protein. RESULTS: The variant HDAC8 c.356C>G is classified as pathogenic following the ACMG (American College of Medical Genetics and Genomics)/AMP (Association for Molecular Pathology) guidelines. By molecular modeling, we confirmed the deleterious effect of this variant, since the amino acid change compromises the conformational flexibility of the HDAC8 loop required for optimal catalytic function. CONCLUSION: We described a novel Thr119Arg mutation in HDAC8 in a patient displaying the major phenotypic traits of the CdLS. Our results suggest that a modest change outside an active site is capable of triggering global structural changes that propagate through the protein scaffold to the catalytic site, creating de facto haploinsufficiency.

PDS5A and PDS5B in Cohesin Function and Human Disease.

Precocious dissociation of sisters 5 (PDS5) is an associate protein of cohesin that is conserved from yeast to humans. It acts as a regulator of the cohesin complex and plays important roles in various cellular processes, such as sister chromatid cohesion, DNA damage repair, gene transcription, and DNA replication. Vertebrates have two paralogs of PDS5, PDS5A and PDS5B, which have redundant and unique roles in regulating cohesin functions. Herein, we discuss the molecular characteristics and functions of PDS5, as well as the effects of its mutations in the development of diseases and their relevance for novel therapeutic strategies.

[Phenotypic and mutation analysis of a fetus with Cornelia de Lange syndrome â ].

OBJECTIVE: To carry out genetic testing for an abortus suspected with Cornelia de Lange syndrome (CdLS). METHODS: History of gestation and the family was taken. Combined with prenatal ultrasonography and the phenotype of the abortus, a diagnosis was made for the proband. Fetal tissue and peripheral blood samples of its parents were collected for the extraction of genomic DNA. Whole exome sequencing was carried out to detect mutations related to the phenotype. Suspected mutations were verified in the parents through Sanger sequencing. RESULTS: Prenatal ultrasound found that the forearms and hands of the fetus were anomalous, in addition with poorly formed vermis cerebellum, slight micrognathia, and increased echo of bilateral renal parenchyma. Examination of the abortus has noted upper limb and facial malformations. Whole exome sequencing revealed that the fetus carried a heterozygous c.2118delG (p.Lys706fs) frameshift mutation of the NIPBL gene. The same mutation was not found in either parent. CONCLUSION: The heterozygous c.2118delG (p.Lys706fs) frameshift mutation of the NIPBL gene probably underlies the CdLS in the fetus. Above finding has provided a basis for the genetic counseling for the family.

Phenotypic and mutation analysis of a fetus with Cornelia de Lange syndrome Ⅰ / 中华医学遗传学杂志

OBJECTIVE@#To carry out genetic testing for an abortus suspected with Cornelia de Lange syndrome (CdLS).@*METHODS@#History of gestation and the family was taken. Combined with prenatal ultrasonography and the phenotype of the abortus, a diagnosis was made for the proband. Fetal tissue and peripheral blood samples of its parents were collected for the extraction of genomic DNA. Whole exome sequencing was carried out to detect mutations related to the phenotype. Suspected mutations were verified in the parents through Sanger sequencing.@*RESULTS@#Prenatal ultrasound found that the forearms and hands of the fetus were anomalous, in addition with poorly formed vermis cerebellum, slight micrognathia, and increased echo of bilateral renal parenchyma. Examination of the abortus has noted upper limb and facial malformations. Whole exome sequencing revealed that the fetus carried a heterozygous c.2118delG (p.Lys706fs) frameshift mutation of the NIPBL gene. The same mutation was not found in either parent.@*CONCLUSION@#The heterozygous c.2118delG (p.Lys706fs) frameshift mutation of the NIPBL gene probably underlies the CdLS in the fetus. Above finding has provided a basis for the genetic counseling for the family.

Analysis of clinical and genetic characteristics in 10 Chinese individuals with Cornelia de Lange syndrome and literature review.

BACKGROUND: Cornelia de Lange syndrome (CdLS) is a rare congenital developmental disorder with variable multisystem involvement and genetic heterogeneity. We aimed to analyze the clinical and genetic characteristics of Chinese individuals with CdLS. METHODS: We collected data regarding the neonatal period, maternal status, clinical manifestation, including facial dimorphisms and development, and follow-up treatment for individuals diagnosed with CdLS. In individuals with suspected CdLS, high-throughput sequencing, Sanger sequencing, and real-time qualitative PCR were used to verify the diagnosis. RESULTS: Variants, including six that were novel, were concentrated in the NIPBL (70%), HDAC8 (20%), and SMC3 (10%) genes. We found two nonsense, three splicing, and two deletion variants in NIPBL; a missense variant and an absence variant in HDAC8; and a missense variant in SMC3. Eleven cardinal features of CdLS were present in more than 80% of Chinese individuals. Compared with non-Chinese individuals of diverse ancestry, there were significant differences in the clinical characteristics of eight of these features. CONCLUSION: Six novel pathological variants were identified; thus, the study expanded the gene variant spectrum. Furthermore, most cardinal features of CdLS found in Chinese individuals were also found in individuals from other countries. However, there were significant differences in eight clinical features.

Complex nutritional deficiencies in a large cohort of Italian patients with Cornelia de Lange syndrome spectrum.

Cornelia de Lange syndrome Spectrum (CdLSp) is characterized by intellectual disability, facial dysmorphisms, and growth impairment. Although eating difficulties are a well-known feature of the disease, there is no data regarding the nutritional deficiencies of these patients. The food intake was tracked using a dietary transcription provided by the family/caregivers, biochemical nutritional parameters were measured with laboratory tests and through an accurate clinical evaluation of the incidence of qualitative and quantitative imbalances in a cohort of 73 patients with CdLSp ware determined. Of these 73, 62 (85%) subjects provided a complete and detailed dietary transcription. In the studied population, a quantitative caloric imbalance in 47/62 (76%) subjects was observed. The caloric intake was low in 27/62 (43%) subjects whereas excessive in 20/62 (33%). Only 15/62 (24%) had an optimum caloric intake. Regarding micronutrients, a calcium intake deficiency in 32% of the patients (20/62) was observed. Blood tests revealed a low iron level in 22/73 (30%) of the patients and 25(OH)D deficiency in 49/73 (67%). Serum hypocalcemia was not evidenced. Qualitative and quantitative imbalances resulted in more frequent than expected in CdLSp patients. A qualitative imbalance was more prevalent in younger patients while in older patients prevailed mainly a quantitative disproportion. We found no statistically meaningful correlation between dietary imbalances, genetic, or clinical parameters. Our findings highlight the need for further studies to evaluate the basal metabolic rate of CdLSp patients and find a correlation with their growth impairment.

Delineation of phenotypes and genotypes related to cohesin structural protein RAD21.

RAD21 encodes a key component of the cohesin complex, and variants in RAD21 have been associated with Cornelia de Lange Syndrome (CdLS). Limited information on phenotypes attributable to RAD21 variants and genotype-phenotype relationships is currently published. We gathered a series of 49 individuals from 33 families with RAD21 alterations [24 different intragenic sequence variants (2 recurrent), 7 unique microdeletions], including 24 hitherto unpublished cases. We evaluated consequences of 12 intragenic variants by protein modelling and molecular dynamic studies. Full clinical information was available for 29 individuals. Their phenotype is an attenuated CdLS phenotype compared to that caused by variants in NIPBL or SMC1A for facial morphology, limb anomalies, and especially for cognition and behavior. In the 20 individuals with limited clinical information, additional phenotypes include Mungan syndrome (in patients with biallelic variants) and holoprosencephaly, with or without CdLS characteristics. We describe several additional cases with phenotypes including sclerocornea, in which involvement of the RAD21 variant is uncertain. Variants were frequently familial, and genotype-phenotype analyses demonstrated striking interfamilial and intrafamilial variability. Careful phenotyping is essential in interpreting consequences of RAD21 variants, and protein modeling and dynamics can be helpful in determining pathogenicity. The current study should be helpful when counseling families with a RAD21 variation.