Disruption of the blood-brain barrier in 22q11.2 deletion syndrome.

Neuroimmune dysregulation is implicated in neuropsychiatric disorders including schizophrenia. As the blood-brain barrier is the immunological interface between the brain and the periphery, we investigated whether this vascular phenotype is intrinsically compromised in the most common genetic risk factor for schizophrenia, the 22q11.2 deletion syndrome (22qDS). Blood-brain barrier like endothelium differentiated from human 22qDS+schizophrenia-induced pluripotent stem cells exhibited impaired barrier integrity, a phenotype substantiated in a mouse model of 22qDS. The proinflammatory intercellular adhesion molecule-1 was upregulated in 22qDS+schizophrenia-induced blood-brain barrier and in 22qDS mice, indicating compromise of the blood-brain barrier immune privilege. This immune imbalance resulted in increased migration/activation of leucocytes crossing the 22qDS+schizophrenia blood-brain barrier. We also found heightened astrocyte activation in murine 22qDS, suggesting that the blood-brain barrier promotes astrocyte-mediated neuroinflammation. Finally, we substantiated these findings in post-mortem 22qDS brain tissue. Overall, the barrier-promoting and immune privilege properties of the 22qDS blood-brain barrier are compromised, and this might increase the risk for neuropsychiatric disease.

Prioritizing Genetic Contributors to Cortical Alterations in 22q11.2 Deletion Syndrome Using Imaging Transcriptomics.

22q11.2 deletion syndrome (22q11DS) results from a hemizygous deletion that typically spans 46 protein-coding genes and is associated with widespread alterations in brain morphology. The specific genetic mechanisms underlying these alterations remain unclear. In the 22q11.2 ENIGMA Working Group, we characterized cortical alterations in individuals with 22q11DS (n = 232) versus healthy individuals (n = 290) and conducted spatial convergence analyses using gene expression data from the Allen Human Brain Atlas to prioritize individual genes that may contribute to altered surface area (SA) and cortical thickness (CT) in 22q11DS. Total SA was reduced in 22q11DS (Z-score deviance = -1.04), with prominent reductions in midline posterior and lateral association regions. Mean CT was thicker in 22q11DS (Z-score deviance = +0.64), with focal thinning in a subset of regions. Regional expression of DGCR8 was robustly associated with regional severity of SA deviance in 22q11DS; AIFM3 was also associated with SA deviance. Conversely, P2RX6 was associated with CT deviance. Exploratory analysis of gene targets of microRNAs previously identified as down-regulated due to DGCR8 deficiency suggested that DGCR8 haploinsufficiency may contribute to altered corticogenesis in 22q11DS by disrupting cell cycle modulation. These findings demonstrate the utility of combining neuroanatomic and transcriptomic datasets to derive molecular insights into complex, multigene copy number variants.

[Child psychiatry interventions in patients with 22q11 deletion syndrome: From treatment to prevention]. / Prise en charge pédopsychiatrique des patients présentant un syndrome microdélétionnel 22q11.2 : du soin à la prévention.

22q11.2DS is one of the more frequent genetic syndromes associated to psychiatric symptoms. It has been associated to an increased risk to develop schizophrenia in adolescence or early adulthood. However, psychiatric symptoms appear early on, and should be recognized as soon as possible by child psychiatrists in order to improve the present well-being of children and their family, and to prevent further risks of developing severe and chronic psychiatric diseases later on. In this paper, we present a review of the recent literature concerning the 22q11.2DS syndrome focused on the risk factors that may be associated to an increased risk of psychotic transition. We advocate for the development of systematic specialized child psychiatry consultations for these patients, included in networks with geneticists, adult psychiatrists, and family associations, in order to improve their psychiatric prognosis and to support the development of translational research.

Mapping 22q11.2 Gene Dosage Effects on Brain Morphometry.

Reciprocal chromosomal rearrangements at the 22q11.2 locus are associated with elevated risk of neurodevelopmental disorders. The 22q11.2 deletion confers the highest known genetic risk for schizophrenia, but a duplication in the same region is strongly associated with autism and is less common in schizophrenia cases than in the general population. Here we conducted the first study of 22q11.2 gene dosage effects on brain structure in a sample of 143 human subjects: 66 with 22q11.2 deletions (22q-del; 32 males), 21 with 22q11.2 duplications (22q-dup; 14 males), and 56 age- and sex-matched controls (31 males). 22q11.2 gene dosage varied positively with intracranial volume, gray and white matter volume, and cortical surface area (deletion < control < duplication). In contrast, gene dosage varied negatively with mean cortical thickness (deletion > control > duplication). Widespread differences were observed for cortical surface area with more localized effects on cortical thickness. These diametric patterns extended into subcortical regions: 22q-dup carriers had a significantly larger right hippocampus, on average, but lower right caudate and corpus callosum volume, relative to 22q-del carriers. Novel subcortical shape analysis revealed greater radial distance (thickness) of the right amygdala and left thalamus, and localized increases and decreases in subregions of the caudate, putamen, and hippocampus in 22q-dup relative to 22q-del carriers. This study provides the first evidence that 22q11.2 is a genomic region associated with gene-dose-dependent brain phenotypes. Pervasive effects on cortical surface area imply that this copy number variant affects brain structure early in the course of development.SIGNIFICANCE STATEMENT Probing naturally occurring reciprocal copy number variation in the genome may help us understand mechanisms underlying deviations from typical brain and cognitive development. The 22q11.2 genomic region is particularly susceptible to chromosomal rearrangements and contains many genes crucial for neuronal development and migration. Not surprisingly, reciprocal genomic imbalances at this locus confer some of the highest known genetic risks for developmental neuropsychiatric disorders. Here we provide the first evidence that brain morphology differs meaningfully as a function of reciprocal genomic variation at the 22q11.2 locus. Cortical thickness and surface area were affected in opposite directions with more widespread effects of gene dosage on cortical surface area.

Isolation of right internal carotid artery, persistent proatlantal 1 artery and rete mirabile in a child with 22q11 deletion syndrome.

We report a case of a 2-year-old girl with 22q11 deletion syndrome who underwent studies for cardiac murmur. Ultrasound, computed tomography angiography and digital subtraction angiography revealed an aberrant right subclavian artery and an isolated right internal carotid artery (ICA) originating from the right pulmonary artery. A right carotid rete mirabile (CRM) and a proatlantal (Pa) type 1 artery were also found. We hypothesize that Pa type 1 persistence and CRM development are secondary to the reversal of flow of the isolated ICA.

Confined placental mosaicism for 22q11.2 deletion as the etiology for discordant positive NIPT results.

22q11.2 deletion, the most common microdeletion syndrome within the general population, is estimated to have a prevalence of 1 in 3000 to 6000. Non-invasive prenatal testing has recently expanded to include screening for several microdeletions including 22q11.2. Given the expansion of prenatal screening options to include microdeletions, it is important to understand the limits of this technology and the variety of reasons that a discordant positive result can occur. Here, we describe a case of a pregnant woman who received a positive non-invasive prenatal maternal plasma screen for 22q11.2 deletion. Maternal and postnatal neonatal peripheral blood cytogenetic, PCR, and fluorescence in situ hybridization studies were normal, but the placenta was mosaic for 22q11.2 deletion in two of three biopsy sites. This case illustrates both the complexities of pre- and post-test counseling for microdeletion screening and the potential for a discordant positive microdeletion result because of confined placental mosaicism. © 2017 John Wiley & Sons, Ltd.

Cognitive ability is associated with altered medial frontal cortical circuits in the LgDel mouse model of 22q11.2DS.

We established a relationship between cognitive deficits and cortical circuits in the LgDel model of 22q11 Deletion Syndrome (22q11DS)-a genetic syndrome with one of the most significant risks for schizophrenia and autism. In the LgDel mouse, optimal acquisition, execution, and reversal of a visually guided discrimination task, comparable to executive function tasks in primates including humans, are compromised; however, there is significant individual variation in degree of impairment. The task relies critically on the integrity of circuits in medial anterior frontal cortical regions. Accordingly, we analyzed neuronal changes that reflect previously defined 22q11DS-related alterations of cortical development in the medial anterior frontal cortex of the behaviorally characterized LgDel mice. Interneuron placement, synapse distribution, and projection neuron frequency are altered in this region. The magnitude of one of these changes, layer 2/3 projection neuron frequency, is a robust predictor of behavioral performance: it is substantially and selectively lower in animals with the most significant behavioral deficits. These results parallel correlations of volume reduction and altered connectivity in comparable cortical regions with diminished executive function in 22q11DS patients. Apparently, 22q11 deletion alters behaviorally relevant circuits in a distinct cortical region that are essential for cognitive function.

An increased prevalence of thyroid disease in children with 22q11.2 deletion syndrome.

We reviewed the health records of pediatric patients with 22q11.2 deletion syndrome (22q11.2 DS) seen over a 5-year period in our 22q11.2 DS multidisciplinary clinic. We determined the prevalence of thyroid dysfunction in this population, in comparison to general population data. Statistical tests were applied to investigate trends in gender differences, thyroid disease subtype and co-morbid conditions in the patients identified with thyroid disease. Of 169 subjects (92 male, 77 female) 9.5% had overt thyroid disease; of these, 1.8% had hyperthyroidism and 7.7% had hypothyroidism; 42% of patients with subclinical or prodromal thyroid disease progressed to overt disease. Our data indicate that thyroid disease prevalence in the 22q11DS pediatric population is significantly higher than that in the general pediatric population Furthermore, over 1/3 of patients in our study population who presented with subclinical thyroid disease progressed to overt disease, requiring medical therapy. Thyroid disease screening should be incorporated into routine medical management of children with 22q11.2 DS. Guidelines for screening individuals with 22q11.2 DS are presented.

[Catch-22? Wide variety of phenotypes associated with the chromosome 22q11 deletion syndrome in two patients]. / A 22-es csapdája? A 22q11 kromoszóma deletiós szindróma változatos klinikai megjelenése két eset kapcsán.

The chromosome 22q11 deletion syndrome may present with a variety of phenotypes. Its symptoms generally include a characteristic facial dysmorphisms and multiplex developmental disorders. Fluorescence in situ hybridization is the current method of choice for the diagnosis if typical multiple defects and/or symptoms are present. The authors present the history of two patients who were followed-up for minor anomalies and various developmental disorders for several years in the genetic counseling office of the authors, but definitive diagnosis was not established. However, when DNA samples of the two patients were recently tested with array comparative genome hybridization, a diagnostic method which has already been used in their institute for several years, the results indicated deletion of the 11.2 region on the long arm of chromosome 22 in both patients. The authors draw attention to the incidence and wide phenotypic spectrum of the chromosome 22q11 deletion syndrome, and show that its identification can be aided with the novel molecular cytogenetic method available in their laboratory.

[NEGATIVE IMPACT OF CHROMOSOME 22Q11 MICRODELETION ON RESULTS OF TREATMENT IN PATIENTS, SUFFERING CONONTRUNCAL FAILURES OF HEART AND MAIN AORTO-PULMONARY COLLATERAL ARTERIES].

Dependence of results of surgical treatment in 42 patients, suffering conotruncal failures and main aorto-pulmonary collateral arteries from presence of the chromosome 22q11 deletion syndrome, was analyzed. While presence of the chromosome 22q11 deletion syndrome duration of treatment of patients in intensive therapy unit and artificial pulmonary ventilation are longer, pressure in a pulmonary artery system after radical operative failures correction is higher, general lethality is bigger, than while the chromosome 22q11 deletion syndrome absence. The data obtained must be taken into account while determining tactics of treatment in patients with confirmed diagnosis of the chromosome 22q11 deletion syndrome.

Retrospective analysis of TREC based newborn screening results and clinical phenotypes in infants with the 22q11 deletion syndrome.

PURPOSE: Population-based newborn screening using T-cell receptor excision circles (TREC) identifies infants with severe T-lymphopenia, seen in severe combined immunodeficiencies (SCID), but also infants with the 22q11 deletion syndrome (22q11DS). Methods for analysis of kappa-deleting recombination excision circles (KREC) help identifying infants with B-lymphopenia. We aimed to evaluate the occurrence of abnormal TREC or KREC newborn screening results in 22q11DS patients and assessed the clinical relevance of abnormal screening reports. METHODS: Simultaneous TREC and KREC analysis was performed on stored original Guthrie cards. Patients with abnormal screening reports were compared to patients with normal reports, regarding lymphocyte counts and clinical severity, obtained by retrospective analysis of medical charts. RESULTS: Of 48 included patients, nine (19 %) had abnormal TREC copy numbers. All 22q11DS patients with abnormal TRECs had CD3+ T-lymphopenia at the time of diagnosis, but only one patient had the complete DiGeorge syndrome. Identified 22q11DS patients with abnormal TREC copy numbers showed significantly lower CD8+ T-lymphocytes at time-of-diagnosis and were significantly more prone to viral infections, compared to 22q11DS patients with normal TREC copy numbers. All 22q11DS patients showed KREC copies within the normal range. CONCLUSIONS: In this retrospective study a high proportion of 22q11DS patients were identified by TREC-based newborn screening. Although only one of them had the complete DiGeorge syndrome with no T-lymphocytes, all of them had T-lymphopenia and most of them had recurrent viral infections, as well as other medical problems, warranting early recognition of the syndrome.

White matter microstructural abnormalities in girls with chromosome 22q11.2 deletion syndrome, Fragile X or Turner syndrome as evidenced by diffusion tensor imaging.

Children with chromosome 22q11.2 deletion syndrome (22q11.2DS), Fragile X syndrome (FXS), or Turner syndrome (TS) are considered to belong to distinct genetic groups, as each disorder is caused by separate genetic alterations. Even so, they have similar cognitive and behavioral dysfunctions, particularly in visuospatial and numerical abilities. To assess evidence for common underlying neural microstructural alterations, we set out to determine whether these groups have partially overlapping white matter abnormalities, relative to typically developing controls. We scanned 101 female children between 7 and 14years old: 25 with 22q11.2DS, 18 with FXS, 17 with TS, and 41 aged-matched controls using diffusion tensor imaging (DTI). Anisotropy and diffusivity measures were calculated and all brain scans were nonlinearly aligned to population and site-specific templates. We performed voxel-based statistical comparisons of the DTI-derived metrics between each disease group and the controls, while adjusting for age. Girls with 22q11.2DS showed lower fractional anisotropy (FA) than controls in the association fibers of the superior and inferior longitudinal fasciculi, the splenium of the corpus callosum, and the corticospinal tract. FA was abnormally lower in girls with FXS in the posterior limbs of the internal capsule, posterior thalami, and precentral gyrus. Girls with TS had lower FA in the inferior longitudinal fasciculus, right internal capsule and left cerebellar peduncle. Partially overlapping neurodevelopmental anomalies were detected in all three neurogenetic disorders. Altered white matter integrity in the superior and inferior longitudinal fasciculi and thalamic to frontal tracts may contribute to the behavioral characteristics of all of these disorders.

Immunological features of 22q11 deletion syndrome.

PURPOSE OF REVIEW: 22q11 deletion syndrome is the most common genetic abnormality. More patients are surviving cardiac surgery, and many do not have cardiac anomalies. Adult patients are now being described. It is important for paediatricians, and increasingly adult physicians, to be aware of the optimum management of these patients. RECENT FINDINGS: Three main immunological patterns are recognized, namely, athymic and incomplete 22q11 deletion syndrome and autoimmunity. Newborn screening for severe combined immunodeficiency detects athymic patients, although diagnosis may be complicated, and instructive cases are described. Incomplete 22q11 deletion syndrome is the most common presentation; new findings predict which patients are likely to experience significant infection. B lymphocyte deficiencies are often overlooked. Data regarding autoimmunity in adult patients is reported, as well as newly reported immunological findings. Finally, management guidelines are now published, and these are highlighted. SUMMARY: Newborn screening detects patients with athymic 22q11 deletion syndrome, but significant illness may complicate the picture, and dual diagnoses can confound treatment. Treatment options for these patients are becoming clearer. Hypoparathyroidism is associated with more severe infection, and immunoglobulin abnormalities are more common than previously recognized. Adult patients are symptomatic and management guidelines will help general physicians in managing these patients.

Atypical developmental trajectory of functionally significant cortical areas in children with chromosome 22q11.2 deletion syndrome.

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is a neurogenetic disorder associated with neurocognitive impairments. This article focuses on the cortical gyrification changes that are associated with the genetic disorder in 6-15-year-old children with 22q11.2DS, when compared with a group of age-matched typically developing (TD) children. Local gyrification index (lGI; Schaer et al. [2008]: IEEE Trans Med Imaging 27:161-170) was used to characterize the cortical gyrification at each vertex of the pial surface. Vertex-wise statistical analysis of lGI differences between the two groups revealed cortical areas of significant reduction in cortical gyrification in children with 22q11.2DS, which were mainly distributed along the medial aspect of each hemisphere. To gain further insight into the developmental trajectory of the cortical gyrification, we examined age as a factor in lGI changes over the 6-15 years of development, within and across the two groups of children. Our primary results pertaining to the developmental trajectory of cortical gyrification revealed cortical regions where the change in lGI over the 6-15 years of age was significantly modulated by diagnosis, implying an atypical development of cortical gyrification in children with 22q11.2DS, when compared with the TD children. Significantly, these cortical areas included parietal structures that are associated, in typical individuals, with visuospatial, attentional, and numerical cognition tasks in which children with 22q11.2DS show impairments.

Functional outcomes of adults with 22q11.2 deletion syndrome.

PURPOSE: The 22q11.2 deletion syndrome is a common multisystem genomic disorder with congenital and later-onset manifestations, including congenital heart disease, intellectual disability, and psychiatric illness, that may affect long-term functioning. There are limited data on adult functioning in 22q11.2 deletion syndrome. METHODS: We used the Vineland Adaptive Behavior Scales to assess functioning in 100 adults with 22q11.2 deletion syndrome (n = 46 male; mean age = 28.8 (standard deviation = 9.7) years) where intellect ranged from average to borderline (n = 57) to mild intellectual disability (n = 43). RESULTS: More than 75% of the subjects scored in the functional deficit range. Although personal, vocational, and financial demographics confirmed widespread functional impairment, daily living skills and employment were relative strengths. Intelligence quotient was a significant predictor (P < 0.001) of overall and domain-specific adaptive functioning skills. A diagnosis of schizophrenia was a significant predictor (P < 0.05) of overall adaptive functioning, daily living skills, and socialization scores. Notably, congenital heart disease, history of mood/anxiety disorders, sex, and age were not significant predictors of functioning. CONCLUSION: Despite functional impairment in adulthood that is primarily mediated by cognitive and psychiatric phenotypes, relative strengths in activities of daily living and employment have important implications for services and long-term planning. These results may help to inform expectations about outcomes for patients with 22q11.2 deletion syndrome.

Neural substrates of psychosis revealed by altered dependencies between brain activity and white-matter architecture in individuals with 22q11 deletion syndrome.

BACKGROUND: Dysconnectivity has been consistently proposed as a major key mechanism in psychosis. Indeed, disruptions in large-scale structural and functional brain networks have been associated with psychotic symptoms. However, brain activity is largely constrained by underlying white matter pathways and the study of function-structure dependency, compared to conventional unimodal analysis, allows a biologically relevant assessment of neural mechanisms. The 22q11.2 deletion syndrome (22q11DS) constitutes a remarkable opportunity to study the pathophysiological processes of psychosis. METHODS: 58 healthy controls and 57 deletion carriers, aged from 16 to 32 years old,underwent resting-state functional and diffusion-weighted magnetic resonance imaging. Deletion carriers were additionally fully assessed for psychotic symptoms. Firstly, we used a graph signal processing method to combine brain activity and structural connectivity measures to obtain regional structural decoupling indexes (SDIs). We use SDI to assess the differences of functional structural dependency (FSD) across the groups. Subsequently we investigated how alterations in FSDs are associated with the severity of positive psychotic symptoms in participants with 22q11DS. RESULTS: In line with previous findings, participants in both groups showed a spatial gradient of FSD ranging from sensory-motor regions (stronger FSD) to regions involved in higher-order function (weaker FSD). Compared to controls, in participants with 22q11DS, and further in deletion carriers with more severe positive psychotic symptoms, the functional activity was more strongly dependent on the structure in parahippocampal gyrus and subcortical dopaminergic regions, while it was less dependent within the cingulate cortex. This analysis revealed group differences not otherwise detected when assessing the structural and functional nodal measures separately. CONCLUSIONS: Our findings point toward a disrupted modulation of functional activity on the underlying structure, which was further associated to psychopathology for candidate critical regions in 22q11DS. This study provides the first evidence for the clinical relevance of function-structure dependency and its contribution to the emergence of psychosis.

Neuroanatomy in adolescents and young adults with 22q11 deletion syndrome: comparison to an IQ-matched group.

22q11 deletion syndrome (22q11DS) is a common genetic condition associated with learning disability and high risk for psychiatric illness, in particular schizophrenia. Previous neuroimaging studies in children and adults with 22q11DS have uncovered a number of abnormalities, but have not differentiated between features relating to cognitive impairment and features relating to risk for schizophrenia. This structural MRI study compares adolescents with 22q11DS (n=14) to adolescents with idiopathic learning disability (n=13) and to typically-developing controls (n=14). Voxel-based morphometry and region-of-interest volumetric analyses were employed to test specific hypotheses based on prior studies of 22q11DS. Features that differentiated 22q11DS participants from both matched-IQ and higher-IQ controls were total white matter volume reduction, occipito-parietal and anterior temporal grey matter reduction, frontal and insula grey matter enlargement, and corpus callosum enlargement. On the other hand, hippocampal volume and cerebellar hemisphere reductions differed between 22q11DS and higher-IQ controls only. The neuroanatomical substrates for cognitive impairment and psychiatric illness in 22q11DS are at least partially separable. Correlations between regional volumetric abnormalities and age suggest that exaggerated processes of normal adolescent brain maturation contribute to psychosis-risk in 22q11DS, consistent with previous findings in childhood-onset schizophrenia.

COMT Val(158) met genotype and striatal D(2/3) receptor binding in adults with 22q11 deletion syndrome.

Although catechol-O-methyltransferase (COMT) activity evidently affects dopamine function in prefrontal cortex, the contribution is assumed less significant in striatum. We studied whether a functional polymorphism in the COMT gene (Val(158) Met) influences striatal D(2/3) R binding ratios (D(2/3) R BP(ND) ) in 15 adults with 22q11 deletion syndrome and hemizygous for this gene, using single photon emission computed tomography and the selective D(2/3) radioligand [(123) I]IBZM. Met hemizygotes had significantly lower mean D(2/3) R BPND than Val hemizygotes. These preliminary data suggest that low COMT activity may affect dopamine levels in striatum in humans and this may have implications for understanding the contribution of COMT activity to psychiatric disorders.

Abnormal nodal and global network organization in resting state functional MRI from subjects with the 22q11 deletion syndrome.

The 22q11 deletion syndrome is a genetic disorder associated with a high risk of developing psychosis, and is therefore considered a neurodevelopmental model for studying the pathogenesis of schizophrenia. Studies have shown that localized abnormal functional brain connectivity is present in 22q11 deletion syndrome like in schizophrenia. However, it is less clear whether these abnormal cortical interactions lead to global or regional network disorganization as seen in schizophrenia. We analyzed from a graph-theory perspective fMRI data from 40 22q11 deletion syndrome patients and 67 healthy controls, and reconstructed functional networks from 105 brain regions. Between-group differences were examined by evaluating edge-wise strength and graph theoretical metrics of local (weighted degree, nodal efficiency, nodal local efficiency) and global topological properties (modularity, local and global efficiency). Connectivity strength was globally reduced in patients, driven by a large network comprising 147 reduced connections. The 22q11 deletion syndrome network presented with abnormal local topological properties, with decreased local efficiency and reductions in weighted degree particularly in hub nodes. We found evidence for abnormal integration but intact segregation of the 22q11 deletion syndrome network. Results suggest that 22q11 deletion syndrome patients present with similar aberrant local network organization as seen in schizophrenia, and this network configuration might represent a vulnerability factor to psychosis.

Quantitative facial phenotyping for Koolen-de Vries and 22q11.2 deletion syndrome.

The Koolen-de Vries syndrome (KdVS) is a multisystem syndrome with variable facial features caused by a 17q21.31 microdeletion or KANSL1 truncating variant. As the facial gestalt of KdVS has resemblance with the gestalt of the 22q11.2 deletion syndrome (22q11.2DS), we assessed whether our previously described hybrid quantitative facial phenotyping algorithm could distinguish between these two syndromes, and whether there is a facial difference between the molecular KdVS subtypes. We applied our algorithm to 2D photographs of 97 patients with KdVS (78 microdeletions, 19 truncating variants (likely) causing KdVS) and 48 patients with 22q11.2DS as well as age, gender and ethnicity matched controls with intellectual disability (n = 145). The facial gestalts of KdVS and 22q11.2DS were both recognisable through significant clustering by the hybrid model, yet different from one another (p = 7.5 × 10-10 and p = 0.0052, respectively). Furthermore, the facial gestalts of KdVS caused by a 17q21.31 microdeletion and KANSL1 truncating variant (likely) causing KdVS were indistinguishable (p = 0.981 and p = 0.130). Further application to three patients with a variant of unknown significance in KANSL1 showed that these faces do not match KdVS. Our data highlight quantitative facial phenotyping not only as a powerful tool to distinguish syndromes with overlapping facial dysmorphisms but also to establish pathogenicity of variants of unknown clinical significance.