Intellectual characteristics of Prader–Willi syndrome: comparison of genetic subtypes

Advances in genetics have led to an increased understanding of the role of the genotype on behavioural functioning. The purpose of the present study was to examine differences in intellectual functioning in individuals with Prader–Willi syndrome (PWS) with a paternal 15q11–q13 deletion versus maternal uniparental disomy (UPD) of chromosome 15. Measures of intelligence and academic achievement were administered to 38 individuals with PWS (24 with deletion and 14 with UPD). The subjects with UPD had significantly higher verbal IQ scores than those with deletion (P0.01). The magnitude of the difference in verbal IQ was 9.1 points (69.9 versus 60.8 for UPD and deletion PWS subjects, respectively). Only 17% of subjects with the 15q11–q13 deletion had a verbal IQ≥70, while 50% of those with UPD had a verbal IQ≥70. Performance IQ scores did not differ between the two PWS genetic subtype groups. This is the first report to document the difference between verbal and performance IQ score patterns among subjects with PWS of the deletion versus the UPD subtype.     

Sleep disturbances and behavioural problems in adults with Prader–Willi syndrome

Background Individuals with Prader–Willi syndrome (PWS) are at risk of sleep disturbances, such as excessive daytime sleepiness (EDS) and sleep apnoea, and behavioural problems. Sleep disturbances and their relationship with other variables had not been researched extensively in adults with PWS. Method Sleep disturbances and behavioural problems were investigated in adults with genetically confirmed PWS using standardised questionnaires. Results of adults with paternal deletion (n = 45) were compared with those of adults with maternal uniparental disomy (n = 33). Results Eleven adults with PWS (i.e. 15%) had a current sleep problem, mostly night waking problems. Twenty‐six adults with PWS (i.e. 33%) suffered from severe EDS. No differences in prevalence of sleep disturbances between genetic subtypes were found. Seventeen adults with deletion (i.e. 38%) and 17 adults with maternal uniparental disomy (i.e. 52%) had behavioural problems. No significant relationships were found between sleep disturbances and behavioural problems. Conclusions In adults with PWS, EDS is the most common type of sleep disturbance. Men and individuals with relative high body mass index are at increased risk for EDS. More research, aimed at developing a suitable screening instrument for sleep apnoea in adults with PWS, is necessary. Clinical implications of the findings are discussed.     

Differences in behavioural phenotype between parental deletion and maternal uniparental disomy in Prader-Willi syndrome: an ERP study.

OBJECTIVE: Paternal deletion and maternal uniparental disomy are the principal genetic subtypes associated with Prader-Willi syndrome (PWS). Recent clinical findings suggest differences in phenotype between these subtypes. The present experimental study addresses this issue using a cognitive psycho-physiological setup. METHODS: Behaviour and event-related brain activity (ERP) was recorded by a continuous performance response inhibition task (CPT-AX) in adults with paternal deletion PWS (n=11), maternal uniparental disomy PWS (n=11) and normal controls (n=11). The dependent behavioural variables of the CPT-AX task were reaction time and correct scores. For the ERPs the N200 and P300 components were included which are related to early modality-specific inhibition and late general inhibition, respectively. RESULTS: The disomy group had fewer correct scores and increased reaction times as compared to the CPT-AX task than the control and deletion group. Both PWS subgroups differed significantly from the control group for the N200 amplitude. Only the control group showed the typical task modulation for the N200 amplitude. The amplitude of the P300 component was considerably smaller in the uniparental disomy group than in the deletion and control groups. CONCLUSIONS: The ERP results suggest that early modality specific inhibition is impaired in both PWS genetic subtypes. Late general inhibition is impaired in the uniparental disomy group only. Thus, although the ERP data suggests a common impairment in early visual inhibition processing, uniparental disomy and parental deletion genetic PWS subtypes clearly differ in their behavioural and brain activation phenotypes. SIGNIFICANCE: The present study is the first experimental demonstration which explains the two principal genetic mechanisms that hinder the expression of the genes at 15q11-q13g in PWS result in different behavioural phenotype.     

Prader–Willi syndrome: new insights in the behavioural and psychiatric spectrum

Prader–Willi syndrome (PWS) is a genetic disorder caused by the loss of the paternal contribution of the proximal part (15q11–q13) of the long arm of chromosome 15 (i.e. deletion, disomy and imprinting mutation). The syndrome is associated with distinct physical dysmorphism, as well as with specific behavioural and psychopathological characteristics. Psychiatric symptoms in adolescence and adulthood have been described, including acute cycloid psychosis, and obsessive compulsive, bipolar and pervasive developmental disorders. At the Centre for Human Genetics in Leuven, Belgium, 53 individuals (31 children and adolescents, and 22 adults) have been followed up for 15 years by a special multidisciplinary team. Attention was given to their medical, cognitive, behavioural and emotional development, and the evolution of psychiatric disorders in adolescence and adulthood. This study describes the psychiatric problems in four patients diagnosed with acute cycloid psychosis and traces their development from infancy to adolescence. Four other individuals needed psychiatric evaluation and treatment, and could be diagnosed as having unspecified bipolar disorder, also termed unstable mood disorder. Both groups were compared, and significant differences in early development and later evolution into adulthood were noted. The individuals with PWS who later developed psychotic episodes were described as active and extrovert toddlers, and showed autistic behaviour during their primary school education. Their intellectual functioning was in the moderate to severely retarded range. The individuals with PWS who later developed an unstable mood disorder were described as rather passive and introvert toddlers, and they presented less disturbed behaviour during their primary school education. The intellectual functioning of these subjects was in the normal to borderline range.     

Behavioural and cognitive abnormalities in an imprinting centre deletion mouse model for Prader–Willi syndrome

The genes in the imprinted cluster on human chromosome 15q11–q13 are known to contribute to psychiatric conditions such as schizophrenia and autism. Major disruptions of this interval leading to a lack of paternal allele expression give rise to Prader–Willi syndrome (PWS), a neurodevelopmental disorder with core symptoms of a failure to thrive in infancy and, on emergence from infancy, learning disabilities and over‐eating. Individuals with PWS also display a number of behavioural problems and an increased incidence of neuropsychiatric abnormalities, which recent work indicates involve aspects of frontal dysfunction. To begin to examine the contribution of genes in this interval to relevant psychological and behavioural phenotypes, we exploited the imprinting centre (IC) deletion mouse model for PWS (PWS‐IC^+/?) and the five‐choice serial reaction time task (5‐CSRTT), which is primarily an assay of visuospatial attention and response control that is highly sensitive to frontal manipulations. Locomotor activity, open‐field behaviour and sensorimotor gating were also assessed. PWS‐IC^+/? mice displayed reduced locomotor activity, increased acoustic startle responses and decreased prepulse inhibition of startle responses. In the 5‐CSRTT, the PWS‐IC^+/? mice showed deficits in discriminative response accuracy, increased correct reaction times and increased omissions. Task manipulations confirmed that these differences were likely to be due to impaired attention. Our data recapitulate several aspects of the PWS clinical condition, including findings consistent with frontal abnormalities, and may indicate novel contributions of the imprinted genes found in 15q11–q13 to behavioural and cognitive function generally.     

Water intake and risk of hyponatraemia in Prader–Willi syndrome

Background and Methods Unusual water intake and drinking behaviour has occasionally been observed in individuals with Prader–Willi syndrome (PWS). The aim of this study is to explore whether this observation is a part of the PWS phenotype and what the consequences may be. The parents of 51 individuals with PWS (age range 2–40 years) were asked by questionnaire to answer on past and present water intake, drinking behaviour, fluid preferences and medical treatment in their PWS‐affected and unaffected children. Questionnaires with information on 47 PWS individuals and 17 without PWS were returned for analysis. The questionnaire information was complemented with information from the individual's medical records. Siblings to PWS individuals made up the control group. The study was approved by the regional medical research ethics committee. Results During infancy, 36 (76%) individuals with PWS disliked water without any flavouring and had an extremely small daily intake of water. Seven individuals (15%) increased the daily water intake to unusually high amounts. In 45 the clinical PWS diagnosis was confirmed by molecular (genetic) testing: nine of them with a confirmed PWS diagnosis had a deletion of chromosome 15q11‐13, in nine individuals no deletion was identified. The majority of individuals who increased their water consumption to extreme values belonged to the non‐deletion group. Two in the non‐deletion group developed hyponatraemia while receiving psychiatric medication. Conclusions Infants with PWS seem to be predisposed to unusual drinking behaviour. They dislike and have an unusually small intake of pure water without flavouring, and most of them continue this even after infancy. Some individuals, especially those without deletion, increase their fluid intake and also accept pure water. They have an increased risk of developing water retention and severe hyponatraemia if exposed to medication known to cause side effects like the syndrome of inappropriate antidiuretic hormone secretion. Perhaps this behaviour is just secondary to overeating; perhaps it is a result of a dysfunction of the hypothalamic nuclei engaged in antidiuretic hormone production.     

'Hungry Eyes': visual processing of food images in adults with Prader-Willi syndrome

Background   Prader-Willi syndrome (PWS) is a genetic disorder associated with intellectual disabilities, compulsivity, hyperphagia and increased risks of life-threatening obesity. Food preferences in people with PWS are well documented, but research has yet to focus on other properties of food in PWS, including composition and suitability for consumption. It is also unclear how food perceptions differ across the two major genetic subtypes of PWS.
Methods   This study examined neural responses to food stimuli in 17 adults with PWS, nine with paternal deletions and eight with maternal uniparental disomy (UPD), and in nine age-matched typical controls. Visual event-related potentials (ERPs) were recorded in response to food images varying in food composition and suitability for consumption during a passive viewing paradigm.
Results   Group differences were observed for the N1 and P3 responses reflecting perceptual categorisation and motivational relevance respectively. The deletion group categorised food stimuli in terms of composition while the UPD group performed more similar to the controls, and focused on the suitability of food for consumption. Individual differences in N1 amplitude correlated with body mass index and scores on the Hyperphagia Questionnaire.
Conclusion   Differences are seen in how people with PWS because of deletion or UPD perceive visual food stimuli even within the first milliseconds of stimuli exposure. Implications are discussed for in vivo food behaviours and for future ERP or neuroimaging studies on hunger, satiety and food perception in PWS.     

Academic underachievement by people with Prader–Willi syndrome

Background Prader–Willi syndrome (PWS) is a genetically determined neurodevelopmental disorder that is associated with the under‐expression of maternally imprinted genes at the 15q11–q13 chromosomal locus. In addition to a characteristic physical and behavioural phenotype, those with the syndrome have impaired social cognition, literal mindedness and inflexibility. The present authors investigated the relationship between the PWS cognitive and behavioural phenotype, educational experience, and levels of attainment in reading, writing and arithmetic. Methods All subjects from a population‐based sample of people with PWS, augmented by those with PWS living in other regions together with a contrast group of people with learning disability (LD) of other aetiologies, are included in the present study. Those children over 3 years of age whose families consented or adults who themselves consented were assessed for ability and attainment (over 7 years of age), and information on functional ability was also obtained from an informant. Underachievement was defined as the difference between the score predicted from full‐scale IQ and the actual achievement score. Results Commonly, levels of achievement were lower than would have been predicted on the basis of IQ among those in the groups with PWS and LD. In the group with PWS, underachievement across academic domains was positively correlated with the percentage of time in education in a special school and negatively correlated with Vineland Socialization domain standard score. There were no across‐domain significant correlations in the group with LD. When using multiple regression analysis, the percentage of time in special school was the only predictor of underachievement and only in the group with PWS. However, some children with PWS in special schools did achieve as expected in at least one academic domain. Conclusions Children with PWS may be placed in special schools largely because of their behavioural problems or physical disabilities, or expectations based on their PWS status. Their intellectual abilities may well be masked by their immature social behaviour. The present authors propose that a failure to recognize and address the specific educational needs which follow from this combination of poor socialization skills and complex maladaptive behaviours, in the context of relatively mild LD, may explain their findings.     

A measure of food seeking in individuals with Prader–Willi syndrome

Background Individuals with Prader–Willi syndrome (PWS), a chromosome 15 genetic disorder, often have a significant preoccupation with food and problem behaviour related to food seeking is often prevalent. Methods In the present study, we compared how individuals with PWS responded on a survey regarding the acceptability of food in various locations that varied according to degree of appropriateness for human consumption (e.g. food on a plate, food in a garbage can). For a subgroup of participants, we observed how they actually responded when placed in a room with food items placed in the same locations depicted in the survey. In the first part of the study, three groups (25 typically developing individuals, 7 individuals with intellectual disability (ID), and 19 individuals with PWS) responded to a visual survey to determine the degree of acceptability of food items in various locations (e.g. on a table near a hairbrush, on the floor behind a toy box, in a trash can). In the second part of the study, these food items (popcorn, jelly beans) were placed in the 12 locations described above. Nine individuals diagnosed with PWS (deletion type) and three individuals with ID were given some break time in the room for 15 min. The amount of food consumed, the time spent food seeking, and time spent interacting with materials were measured. Results Results of the survey indicated that the PWS group differed significantly with regard to how they responded on the survey from the typically developing group, but did not differ significantly from the ID group. Results of the food seeking observations indicated that only three individuals with PWS ate a significant number of items. The three individuals did not differ from the rest of the group according to IQ or compulsivity score; however, they had significantly lower body mass index (BMI) scores and were younger than the other participants. Conclusions The findings from the survey indicate that individuals with PWS are able to discriminate the appropriateness of eating items in more or less contaminated areas; however, the amount of time spent seeking food and the amount of food covertly consumed appeared to depend more directly on age and BMI.     

Cognitive abilities and genotype in a population-based sample of people with Prader–Willi syndrome

Background Prader–Willi syndrome (PWS) is characterized by extreme floppiness at birth, impaired sexual development, short stature, severe over‐eating, characteristic physical features and learning disabilities (LD). Impaired social cognition, literal mindedness and cognitive inflexibility are also present. The syndrome has two main genetic subtypes that both result in the failure of expression of maternally imprinted genes on chromosome 15 at the locus q11‐13. Methods Through multiple sources, we attempted to identify all people with PWS living in one health region in the UK. Additional people with PWS identified in other regions were also recruited to augment the study sample. A comparison group of people with LD as a result of aetiologies other than PWS was also identified. All people from these three groups, over age three, who gave their consent, were assessed using tests of ability and attainment. In addition, their main carers were interviewed using a semistructured interview. Blood samples for genetic diagnosis were obtained from all consenting participants. Findings The IQ distribution of the population sample was approximately normal with a mean IQ 40 points below that of the general population. There were systematic differences between the two main genetic subtypes. Those with disomies differed in cognitive profiles from both those with deletions and the comparison LD group (the latter two groups were very similar) in terms of better verbal abilities and impaired coding ability. Some people with PWS deletions had strong visuospatial skills. Interpretation We propose that the normal distribution of IQ, shifted downwards relative to that of the general population, is the result of a global effect on IQ of the PWS gene(s), and that the different cognitive profile seen in those with chromosome 15 maternal disomies is a specific effect of a gene, or genes, on chromosome 15 which is differentially either expressed or not expressed in those with disomies relative to those with deletions. One hypothesis is that these subtle cognitive differences are a manifestation of the genetic influences of gender‐specific imprinted genes on cerebral lateralization. This requires further investigation.     

Compulsive behavior in Prader-Willi syndrome: examining severity in early childhood

Prader-Willi syndrome (PWS) is a genetic disorder characterized by hyperphagia and food preoccupations. Researchers indicate that individuals with PWS, including young children, exhibit food and non-food-related compulsions. Normative rituals are also often present among typically developing preschoolers. However, it is unclear how these behaviors affect the child. Although preschoolers with PWS exhibit more types of rituals than other populations, it is uncertain if the severity of these behaviors differs from the rituals experienced during normative development. Thus, the purpose of this research was to determine whether the ritualistic behaviors exhibited by preschoolers with PWS differ in severity from those exhibited during normative development. We also sought to identify whether non-food ritualistic behavior was related to the hyperphagia in PWS. Parents of 68 children with PWS, 86 typically developing children, and 57 children with developmental delays completed questionnaires on rituals and eating behavior. Children with PWS exhibited more severe ritualistic behavior than typically developing children but not other children with developmental delays. However, the severity of non-food-related rituals was related to the severity of eating behavior in PWS. We hypothesize that this link between hyperphagia and non-food-related compulsivity may share a common underlying neurobiological mechanism.     

Cognitive profile in a large french cohort of adults with Prader–Willi syndrome: differences between genotypes

Background Prader–Willi syndrome (PWS) is a rare genetic disorder characterised by developmental abnormalities leading to somatic and psychological symptoms. These include dysmorphic features, impaired growth and sexual maturation, hyperphagia, intellectual delay, learning disabilities and maladaptive behaviours. PWS is caused by a lack of expression of maternally imprinted genes situated in the 15q11‐13 chromosome region. The origin is a ‘de novo’ deletion in the paternal chromosome in 70% of the cases and a maternal uniparental disomy in 25%. The two main genotypes show differences, notably regarding cognitive and behavioural features, but the mechanisms are not clear. This study assessed cognitive impairment in a cohort of adults with genetically confirmed PWS, analysed their profiles of cognitive strengths and weaknesses, and compared the profiles in terms of genotype. Methods Ninety‐nine male and female adults participated, all inpatients on a specialised unit for the multidisciplinary care of PWS. The Wechsler Adult Intelligence Scale (WAIS‐III) was administered to all patients in identical conditions by the same psychologist. Eighty‐five patients were able to cope with the test situation. Their scores were analysed with non‐parametric statistical tools. The correlations with sex, age and body mass index were explored. Two genotype groups were compared: deletion (n = 57) and non‐deletion (n = 27). Results The distribution of intelligence quotients in the total cohort was non‐normal, with the following values (medians): Full Scale Intelligence Quotient (FSIQ): 52.0 (Q1:46.0; Q3:60.0), Verbal Intellectual Quotient (VIQ): 53.0 (Q1:48; Q3:62) and Performance Intellectual Quotient (PIQ): 52.5 (Q1:48; Q3:61). No correlation was found with sex, age or body mass index. Comparison between groups showed no significant difference in FSIQ or VIQ. PIQ scores were significantly better in the deletion group. The total cohort and the deletion group showed the VIQ = PIQ profile, whereas VIQ > PIQ was observed in the non‐deletion group. The subtest scores in the two groups showed significant differences, with the deletion group scoring better in three subtests: object assembly, picture arrangement and digit symbol coding. Some relative strengths and weaknesses concerned the total cohort, but others concerned only one genotype. Discussion We documented a global impairment in the intellectual abilities of a large sample of French PWS patients. The scores were slightly lower than those reported in most other studies. Our data confirmed the previously published differences in the cognitive profiles of the two main PWS genotypes and offer new evidence to support this hypothesis. These results could guide future neuropsychological studies to determine the cognitive processing in PWS. This knowledge is essential to improve our understanding of gene‐brain‐behaviour relationships and to open new perspectives on therapeutic and educational programmes.     

ADHD symptoms and insistence on sameness in Prader-Willi syndrome

Background Apart from a pervasive eating disorder, the Prader-Willi (PWS) syndrome is characterized by a distinct behavioural profile comprising maladaptive behaviours, obsessive-compulsive traits and skin picking, all included in the PWS behavioural phenotype. In this study, we present a further delineation of this characteristic behavioural profile by screening for indices of executive dysfunctions related to attention-deficit/hyperactivity disorder (ADHD), immature compulsive-like adherence to sameness and skin picking, and how these features aggregate into symptom constellations in children and adolescents with PWS. Method Parents of 58 individuals with PWS (aged 5–18 years) participated by completing Childhood Routines Inventory (CRI) and Conners’ Parent Rating Scale (CPRS-48). Results Results showed that indices of ADHD and excessive insistence on sameness were common, comorbid and of early onset. They were both associated with conduct problems. Skin picking, appearing as a single and comorbid symptom, was less associated with childlike compulsions and ADHD-related problems. Conclusions Findings are discussed in terms of further research in executive dysfunctions in PWS.     

Prader-Willi syndrome: Diagnostic strategy with a cytogenetic and molecular approach

Prader-Willi syndrome (PWS) is a disorder characterized by neonatal hypotonia with poor suck, mild to moderate mental retardation, obesity beginning after 3 yr of age, hypogonadism and characteristic facial features. High resolution cytogenetic studies showed a deletion of the proximal chromosome 15q(q11–q13) region in approximately 50%. Interestingly, the same deletion was described in another distinct mental disorder: the Angelman syndrome (AS). This deletion was confirmed by molecular analyses, and a new mechanism was reported: uniparental disomy (maternal in PWS and paternal in AS) strongly implicate genomic imprinting in this chromosomal region. The principal aim of our group is to apply cytogenetic and molecular biology techniques to perform diagnosis and genetic counselling. Patient studies were usually based on high resolution cytogenetic analysis, quantitative Southern blotting (with D15S9, D15S11, D15S10, D15S12 loci) and dinucleotide repeat polymorphism assay by polymerase chain reaction (PCR) (IR4. 3R and GABARB3). The combination of these different methods allowed us to propose a diagnostic strategy for PWS.     

An investigation of executive function abilities in adults with Prader–Willi syndrome

Background Prader–Willi syndrome (PWS) is a genetic disorder caused by the absence of expression of maternally imprinted genes on the long arm of chromosome 15 (15q 11-13). There are two main genetic sub-types: (1) deletion, caused by the absence of paternally derived genetic material; and (2) uniparental disomy (UPD), where two copies of maternally derived chromosome 15 are present. In addition to generally mild/borderline intellectual disability (ID) and the almost universal feature of hyperphagia, PWS is associated with high rates of behaviour problems including temper tantrums, compulsive behaviour, perseverative speech, skin picking and rigid thinking. The present study seeks to explore whether these behaviours are associated with relative deficits in executive function (EF), which comprises the set of non-automatic processes utilized by an individual when faced with a novel situation. Methods Eighteen adult participants with a clinical diagnosis of PWS (12 with deletion sub-type, 6 with UPD) were recruited from a UK Health Service PWS clinic, and compared with 15 participants of similar age and verbal ability on a series of EF tasks and also Digit Span Forwards. An informant completed two ratings of behaviour, the Aberrant Behavior Checklist (ABC) and the Dysexecutive Questionnaire (DEX). Results The PWS group had significantly higher scores on the ABC but not on the DEX. There were no significant differences between the whole PWS group and the comparison group on any of the EF tasks. The deletion sub-type group was significantly poorer at a non-executive task, Digit Span Forwards. There was an unexpected trend for the deletion sub-type group to show more efficient performance on a visuospatial planning task, the Tower of London (TOL), but this trend did not reach significance. Conclusions The lack of relative deficits in EF task performance does not support the hypothesis that EF differences could account for the high levels of behaviour problems found in PWS. Applying the Baddeley and Hitch model of working memory it is suggested that the PWS group have a relatively intact central executive and visuospatial sketchpad but a relative impairment in the phonological loop, perhaps relating to the capacity of the phonological store. This latter finding seems to be particularly salient for those with a deletion. As differences in EF ability were not found, it is suggested that a region of the brain involved in the modulation of emotion but not particularly with EF, the orbitofrontal cortex (OFC), may be implicated in the behaviour problems reported in PWS.     

Kinetic form discrimination in Prader–Willi syndrome

Discrimination of the shape of motion‐produced forms generated by random elements (i.e. second‐order stimuli varying in element density and temporal correlation) was tested in four groups: (1) subjects with Prader–Willi syndrome (PWS), chromosome 15q deletion subtype; (2) subjects with PWS, uniparental maternal disomy (UPD) subtype; (3) equivalent non‐PWS controls; and (4) normal controls. The performance of the normal controls exceeded that of all other groups (78% correct, P < 0.009). The PWS deletion (66%) and the equivalent control groups (59%) did not differ (P < 0.95). The UPD group performed significantly less well (38%, P < 0.04) than all the other groups. The performance of the PWS deletion and equivalent control groups is consistent with other data indicating that these populations encounter difficulty meeting the processing demands posed by second‐order stimuli. The inferior performance of the UPD group may be attributed to receiving two active alleles of a maternally expressed gene influencing neural development. One candidate is the ubiquitin protein ligase gene (UBE3A), which is maternally expressed only and localized to the 15q region. Other possibilities include the requirement of a paternally expressed gene, residual mosaic trisomy 15 in the brain tissue or complex interactions including specific ratios of differentially spliced gene products.     

Social Responsiveness and Competence in Prader-Willi Syndrome: Direct Comparison to Autism Spectrum Disorder

Prader-Willi syndrome (PWS), a neurodevelopmental disorder primarily characterized by hyperphagia and food preoccupations, is caused by the absence of expression of the paternally active genes in the proximal arm of chromosome 15. Although maladaptive behavior and the cognitive profile in PWS have been well characterized, social functioning has only more recently been systematically examined. Findings to date indicate the social impairment exhibited may reflect specific difficulty interpreting and using social information effectively. In addition, evidence suggests that there is an increased risk of social deficits in people with the maternally-derived uniparental disomy (mUPD) subtype of PWS in comparison to those with 15q11–13 paternal deletion (DEL). Using the Social Responsiveness Scale (SRS) and the Social Competence Inventory, our goal was to compare social functioning in PWS to individuals with autism spectrum disorder (ASD). Participants with mUPD scored similarly to the ASD group across most SRS domains. All groups had difficulty with social competence, although the DEL group scored highest on prosocial behavior. Findings suggest further characterization of social behavior in PWS is necessary to aid in advancing the understanding of the contributions of genes in the 15q11–13 critical region to ASD susceptibility, particularly with respect to the overexpression of maternally expressed genes in this region, as well as aiding in awareness and development/implementation of interventions.     

Subtypes in 22q11.2 deletion syndrome associated with behaviour and neurofacial morphology

22q11.2 deletion syndrome (22q11DS) has a complex phenotype with more than 180 characteristics, including cardiac anomalies, cleft palate, intellectual disabilities, a typical facial morphology, and mental health problems. However, the variable phenotype makes it difficult to predict clinical outcome, such as the high prevalence of psychosis among adults with 22q11DS (～25–30% vs. ～1% in the general population). The purpose of this study was to investigate whether subtypes exist among people with 22q11DS, with a similar phenotype and an increased risk of developing mental health problems. Physical, cognitive and behavioural data from 50 children and adolescents with 22q11DS were included in a k-means cluster analysis. Two distinct phenotypes were identified: Type-1 presented with a more severe phenotype including significantly impaired verbal memory, lower intellectual and academic ability, as well as statistically significant reduced total brain volume. In addition, we identified a trend effect for reduced temporal grey matter. Type-1 also presented with autism-spectrum traits, whereas Type-2 could be described as having more 22q11DS-typical face morphology, being predominately affected by executive function deficits, but otherwise being relatively high functioning with regard to cognition and behaviour. The confirmation of well-defined subtypes in 22q11DS can lead to better prognostic information enabling early identification of people with 22q11DS at high risk of psychiatric disorders. The identification of subtypes in a group of people with a relatively homogenous genetic deletion such as 22q11DS is also valuable to understand clinical outcomes.