Prader-Willi syndrome: A primer for clinicians

Examination of sensory reception and integration abilities in children with and without Prader-Willi syndrome

BACKGROUND

Good postural stability control is dependent upon the complex integration of incoming sensory information (visual, somatosensory, vestibular) with neuromotor responses that are constructed in advance of a voluntary action or in response to an unexpected perturbation.

AIMS

To examine whether differences exist in how sensory inputs are used to control standing balance in children with and without Prader-Willi syndrome (PWS).

METHODS AND PROCEDURES

In this cross-sectional study, 18 children with PWS and 51 children categorized as obese but without PWS (without PWS) ages 8-11 completed the Sensory Organization Test®. This test measures the relative contributions of vision, somatosensory, and vestibular inputs to the control of standing balance. The composite equilibrium score (CES) derived from performance in all sensory conditions, in addition to equilibrium scores (EQs) and falls per condition were compared between groups.

OUTCOMES AND RESULTS

The CES was lower for children with PWS compared to children without PWS (M=53.93, SD=14.56 vs. M=66.17, SD=9.89, p = .001) while EQs declined in both groups between conditions 1 and 4 (F (1.305, 66.577) = 71.381, p < .001). No group differences in the percent of falls were evident in condition 5 but more children with PWS fell in condition 6 (χ2 (1) = 7.468, p = .006). Group differences in frequency of repeated falls also approached significance in conditions 5 (χ2 (3) = 4.630, p = .099) and 6 (χ2 (3) = 5.167, p = .076).

CONCLUSIONS AND IMPLICATIONS

Children with PWS demonstrated a lower overall level of postural control and increased sway when compared to children with obesity. Both the higher incidence and repeated nature of falls in children with PWS in conditions 5 and 6 suggest an inability to adapt to sensory conditions in which vestibular input must be prioritized. Postural control training programs in this population should include activities that improve their ability to appropriately weight sensory information in changing sensory environments, with a particular focus on the vestibular system. WHAT DOES THIS STUDY ADD?: This study shows that children with PWS demonstrate a lower level of postural stability. The results suggest that children with PWS show inability to adapt to sensory conditions that require prioritizing vestibular information to maintain postural control. This information can be used to help guide training programs in this population.

Hormonal Imbalances in Prader-Willi and Schaaf-Yang Syndromes Imply the Evolution of Specific Regulation of Hypothalamic Neuroendocrine Function in Mammals

The hypothalamus regulates fundamental aspects of physiological homeostasis and behavior, including stress response, reproduction, growth, sleep, and feeding, several of which are affected in patients with Prader-Willi (PWS) and Schaaf-Yang syndrome (SYS). PWS is caused by paternal deletion, maternal uniparental disomy, or imprinting defects that lead to loss of expression of a maternally imprinted region of chromosome 15 encompassing non-coding RNAs and five protein-coding genes; SYS patients have a mutation in one of them, MAGEL2. Throughout life, PWS and SYS patients suffer from musculoskeletal deficiencies, intellectual disabilities, and hormonal abnormalities, which lead to compulsive behaviors like hyperphagia and temper outbursts. Management of PWS and SYS is mostly symptomatic and cures for these debilitating disorders do not exist, highlighting a clear, unmet medical need. Research over several decades into the molecular and cellular roles of PWS genes has uncovered that several impinge on the neuroendocrine system. In this review, we will discuss the expression and molecular functions of PWS genes, connecting them with hormonal imbalances in patients and animal models. Besides the observed hormonal imbalances, we will describe the recent findings about how the loss of individual genes, particularly MAGEL2, affects the molecular mechanisms of hormone secretion. These results suggest that MAGEL2 evolved as a mammalian-specific regulator of hypothalamic neuroendocrine function.

Hospital outcomes in pediatric patients with Prader-Willi syndrome (PWS) undergoing orthopedic surgery: A 12-year analysis of national trends in surgical management and inpatient hospital outcomes

BACKGROUND

The incidence of orthopedic disorders amongst patients with Prader-Willi Syndrome (PWS) is high when compared to the general pediatric population. The purpose of this retrospective study was to define the most commonly performed orthopedic procedures in pediatric patients with PWS and to characterize the peri-operative outcomes of these patients.

METHODS

The Kids Inpatient Database (KID) was queried to collect data and identify all pediatric patients with PWS who underwent orthopedic procedures from 2001 to 2012. A total of 3684 patients with PWS were identified, 334 of who underwent an orthopedic procedure. Population demographics, comorbidities, and specific procedures undergone were defined. The incidences of postoperative complications and length of associated hospital stay were additionally evaluated.

RESULTS

Mean age of patients in this sample was 10.33 years (SD 4.5). The most common comorbidities included obesity (18.1%), chronic pulmonary disease (14.1%), hypothyroidism (5.1%), hypertension (5.1%), and uncomplicated diabetes (4%). Common procedures were spinal fusion (165/334, 49%) and lower extremity procedures (50/334, 15%). Complications included acute blood loss anemia, device related complications, pneumonia, sepsis, and urinary tract infections. The overall complication rate was 35.6%. Average hospital lengths of stay for patients undergoing spinal fusion was 6.68 days (SD 4.13), lower extremity orthopedic procedure was 5.65 days (SD 7.4), and all other orthopedic procedures was 7.74 days (SD 16.3).

CONCLUSIONS

Orthopedic disorders are common in patients with PWS. Consequently, spinal fusions and lower extremity procedures are commonly performed in this patient population. Associated comorbid conditions may negatively impact surgical outcomes in these patients. This information should prove useful in the peri-operative management of patients with PWS undergoing orthopedic surgery and for shared decision making with families.

Hospital outcomes of scoliosis surgery in children with Prader-Willi Syndrome: comparison with adolescent idiopathic scoliosis

PURPOSE

The purpose of this study was to evaluate the peri-operative outcomes of patients with Prader-Willi Syndrome (PWS) undergoing spinal deformity correction and compare the outcomes to patients with adolescent idiopathic scoliosis (AIS).

METHODS

A retrospective review of the Kid's Inpatient Database was performed from 2000 to 2012 to identify all pediatric patients with scoliosis undergoing spinal fusion. Cohorts were created on the basis of PWS diagnosis and adolescent idiopathic scoliosis. Statistical analysis was performed for differences in post-operative outcomes between these two patient cohorts.

RESULTS

Between 2000 and 2012, the number of spinal fusions performed increased by 24.6 and 32.2% in the PWS and adolescent idiopathic scoliosis populations, respectively. There was no difference between the incidence of major complications in PWS patients when compared to AIS (1.7% vs. 1.0% in idiopathic scoliosis; p = 0.362). Although there was no significant difference in the rate of overall minor complications, PWS patients were demonstrated to be more likely to experience post-operative pneumonia (p < 0.0001) and implant complications (p < 0.001).

CONCLUSION

Patients with scoliosis associated with PWS do not have any increased risk of major complications following spinal deformity correction when compared to patients with adolescent idiopathic scoliosis. Two important minor complications to keep in mind when surgically treating scoliosis in PWS patients include pulmonary and implant-related complications.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Obesity in Prader-Willi syndrome: physiopathological mechanisms, nutritional and pharmacological approaches

Prader-Willi syndrome (PWS) is a genetic disorder caused by the lack of expression of genes on the paternally inherited chromosome 15q11.2-q13 region. The three main genetic subtypes are represented by paternal 15q11-q13 deletion, maternal uniparental disomy 15, and imprinting defect. Clinical picture of PWS changes across life stages. The main clinical characteristics are represented by short stature, developmental delay, cognitive disability and behavioral diseases. Hypotonia and poor suck resulting in failure to thrive are typical of infancy. As the subjects with PWS age, clinical manifestations such as hyperphagia, temperature instability, high pain threshold, hypersomnia and multiple endocrine abnormalities including growth hormone and thyroid-stimulating hormone deficiencies, hypogonadism and central adrenal insufficiency due to hypothalamic dysfunction occur. Obesity and its complications are the most common causes of morbidity and mortality in PWS. Several mechanisms for the aetiology of obesity in PWS have been hypothesized, which include aberration in hypothalamic pathways of satiety control resulting in hyperphagia, disruption in hormones regulating appetite and satiety and reduced energy expenditure. However, despite the advancement in the research field of the genetic basis of obesity in PWS, there are contradictory data on the management. Although it is mandatory to adopt obesity strategy prevention from infancy, there is promising evidence regarding the management of obesity in adulthood with current obesity drugs along with lifestyle interventions, although the data are limited. Therefore, the current manuscript provides a review of the current evidence on obesity and PWS, covering physiopathological aspects, obesity-related complications and conservative management.

The Interplay Between Pituitary Health and Diabetes Mellitus - The Need for 'Hypophyseo-Vigilance'

The anterior and posterior hypophyseal hormones alter glucose metabolism in health and disease. Secondary diabetes may occur due to hypersecretion of anterior pituitary hormones like adrenocorticotrophic hormone in Cushing's disease and growth hormone in acromegaly. Other hormones like prolactin, gonadotropins, oxytocin and vasopressin, though not overtly associated with causation of diabetes, have important physiological role in maintaining glucose homeostasis. Hypoglycaemia is not an unusual occurrence in hypopituitarism. Many of the medications that are used for treatment of hypophyseal diseases alter glucose metabolism. Agents like pasireotide should be used with caution in the setting of diabetes, whereas pegvisomant should be given preference. Diabetes mellitus itself, on the other hand, can alter the functioning of hypothalamic pituitary axis; this is documented in both type 1 and type 2 diabetes. This review focuses on the clinically relevant interplay of hypophyseal hormones and glucose homeostasis. The authors define 'hypophyseo-vigilance' as an approach which keeps the bidirectional, multifaceted interactions between the pituitary and glucose metabolism in mind while managing diabetes and pituitary disease.

Oral disorders in children with Prader-Willi syndrome: a case control study

INTRODUCTION

Prader-Willi Syndrome (PWS) is a genetic disorder caused by the lack of expression of certain paternal genes located on chromosome 15q11-q13. This anomaly causes cognitive, neurological and endocrine abnormalities, among which one of the most important is hyperphagia. The aim of this study was to assess the oral health of children with PWA and to establish preventive criteria.

RESULTS

Thirty patients with PWS (mean age 10.2 years) and 30 age- and gender-matched controls were included in the study. Twenty-six patients with PWS(86.6%) followed dietary treatment prescribed by their endocrinologist. Individuals with PWS had a mean caries index of 53.3% and Decayed Missing Filled teeth (DMFT) index 2.5, and 53.3% had gingivitis, in the control group the respective figures were 43.3%, 0.93, and 60%. Only the DMFT index (p 0.017) presented significant differences. Regarding stimulated salivary secretion, patients with PWS presented a mean of 0.475 ml/min with a pH of 6.15, while controls presented a mean of 0.848 ml/min with a pH of 7.53; the differences between the groups were statistically significant in both cases (p 0.032 and p 0.0001 respectively). The population with PWS presented a higher plaque index (> 2) than their healthy peers, but the differences were not significant.

CONCLUSION

Pediatric patients with Prader-Willi syndrome have an increased risk of caries and gingivitis. The children with this syndrome have a decreased salivary flow and a more acidic salivary pH. In these patients, dental care is an essential part of their multidisciplinary medical treatment.

Clitoral sizes and anogenital distances in term newborns in Nigeria

BACKGROUND

Previous studies suggest significant ethnic and racial differences in clitoral sizes and anogenital distances in the newborn. This study aimed to document normative data on clitoral sizes and anogenital distances of apparently normal term female infants in Sagamu.

METHODS

The study was a multi-center, cross-sectional descriptive research carried out among 317 female term infants within the first 72 h of life. Interviewer-based questionnaire was applied to obtain sociodemographic data, pregnancy and birth history. A sliding digital caliper was used for measurement. Data analysis was with SPSS version 20.0.

RESULTS

The mean clitoral length was 6.7 ± 1.6 mm while the mean clitoral width was 5.6 ± 0.8 mm. The mean fourchette-clitoris distance, anus-clitoris distance and anus-fourchette distance were 21.9 ± 2.1 mm, 35.5 ± 2.5 mm and 17.0 ± 2.6 mm respectively. The anus-clitoris and anus-fourchette distances significantly correlated with the anthropometric parameters while the clitoral measurements did not.

CONCLUSION

The mean values recorded in this study were higher than observed in most previous studies. This simple, affordable and non-invasive evaluation could aid early diagnosis and treatment of female infants with potentially harmful conditions such as congenital adrenal hyperplasia.

Profiles and trajectories of impaired social cognition in people with Prader-Willi syndrome

Introduction

People with Prader-Willi syndrome (PWS) have a distinctive behavioral phenotype that includes intellectual disability, compulsivity, inattention, inflexibility and insistence on sameness. Inflexibility and inattention are at odds with the cognitive flexibility and attention to social cues needed to accurately perceive the social world, and implicate problems in social cognition. This study assessed two social cognition domains in people with PWS; emotion recognition and social perception. We identified changes in social cognition over an approximate two-year time period (M = 2.23 years), relative strengths and weakness in social cognition, and correlates and predictors of social cognition.

Methods

Emotion recognition and social perception were examined at two time points in 94 individuals with PWS aged 5 to 62 years (M = 13.81, SD = 10.69). Tasks administered included: standardized IQ testing; parent-completed measures of inattention and inflexibility; standard emotion recognition photos (fear, sadness, anger, happy); and videotaped social perception vignettes depicting negative events with either sincere/benign or insincere/hostile interactions between peers.

Results

An atypical trajectory of negative emotion recognition emerged, marked by similar levels of poor performances across age, and confusion between sad and anger that is typically resolved in early childhood. Recognition of sad and fear were positively correlated with IQ. Participants made gains over time detecting social cues, but not in forming correct conclusions about the intentions of others. Accurately judging sincere intentions remained a significant weakness over time. Relative to sincere intentions, participant’s performed significantly better in detecting negative social cues, and correctly judging trickery, deceit and lying. Age, IQ, inattention, and recognition of happy and sad accounted for 29% of variance in social perception.

Conclusion

Many people with PWS have deficits in recognizing sad, anger and fear, and accurately perceiving the sincere intentions of other people. The impact of these deficits on social behavior and relationships need to be better understood.

Requirements for improving health and well-being of children with Prader-Willi syndrome and their families

Prader-Willi syndrome (PWS) is a rare genetic condition with multi-system involvement. The literature was reviewed to describe neurodevelopment and the behavioural phenotype, endocrine and metabolic disorders and respiratory and sleep functioning. Implications for child and family quality of life were explored. Challenging behaviours contribute to poorer well-being and quality of life for both the child and caregiver. Recent evidence indicates healthy outcomes of weight and height can be achieved with growth hormone therapy and dietary restriction and should be the current target for all individuals with PWS. Gaps in the literature included therapies to manage challenging behaviours, as well as understanding the effects of growth hormone on respiratory and sleep function. New knowledge regarding the transition of children and families from schooling and paediatric health services to employment, accommodation and adult health services is also needed. Developing a national population-based registry could address these knowledge gaps and inform advocacy for support services that improve the well-being of individuals with PWS and their families.

Magel2 Modulates Bone Remodeling and Mass in Prader-Willi Syndrome by Affecting Oleoyl Serine Levels and Activity

Among a multitude of hormonal and metabolic complications, individuals with Prader-Willi syndrome (PWS) exhibit significant bone abnormalities, including decreased BMD, osteoporosis, and subsequent increased fracture risk. Here we show in mice that loss of Magel2, a maternally imprinted gene in the PWS critical region, results in reduced bone mass, density, and strength, corresponding to that observed in humans with PWS, as well as in individuals suffering from Schaaf-Yang syndrome (SYS), a genetic disorder caused by a disruption of the MAGEL2 gene. The low bone mass phenotype in Magel2^-/- mice was attributed to reduced bone formation rate, increased osteoclastogenesis and osteoclast activity, and enhanced trans-differentiation of osteoblasts to adipocytes. The absence of Magel2 in humans and mice resulted in reduction in the fatty acid amide bone homeostasis regulator, N-oleoyl serine (OS), whose levels were positively linked with BMD in humans and mice as well as osteoblast activity. Attenuating the skeletal abnormalities in Magel2^-/- mice was achieved with chronic administration of a novel synthetic derivative of OS. Taken together, Magel2 plays a key role in modulating bone remodeling and mass in PWS by affecting OS levels and activity. The use of potent synthetic analogs of OS should be further tested clinically as bone therapeutics for treating bone loss. © 2018 American Society for Bone and Mineral Research.

Hippocampal deficits in neurodevelopmental disorders

Neurodevelopmental disorders result from impaired development or maturation of the central nervous system. Both genetic and environmental factors can contribute to the pathogenesis of these disorders; however, the exact causes are frequently complex and unclear. Individuals with neurodevelopmental disorders may have deficits with diverse manifestations, including challenges with sensory function, motor function, learning, memory, executive function, emotion, anxiety, and social ability. Although these functions are mediated by multiple brain regions, many of them are dependent on the hippocampus. Extensive research supports important roles of the mammalian hippocampus in learning and cognition. In addition, with its high levels of activity-dependent synaptic plasticity and lifelong neurogenesis, the hippocampus is sensitive to experience and exposure and susceptible to disease and injury. In this review, we first summarize hippocampal deficits seen in several human neurodevelopmental disorders, and then discuss hippocampal impairment including hippocampus-dependent behavioral deficits found in animal models of these neurodevelopmental disorders.

Ventilatory Responses During Submaximal Exercise in Children With Prader-Willi Syndrome

PURPOSE

Prader-Willi syndrome (PWS) is a genetic neurobehavioral disorder presenting hypothalamic dysfunction and adiposity. At rest, PWS exhibits hypoventilation with hypercapnia. We characterized ventilatory responses in children with PWS during exercise.

METHODS

Participants were children aged 7-12 years with PWS (n = 8) and without PWS with normal weight (NW; n = 9, body mass index ≤ 85th percentile) or obesity (n = 9, body mass index ≥ 95th percentile). Participants completed three 5-minute ambulatory bouts at 3.2, 4.0, and 4.8 km/h. Oxygen uptake, carbon dioxide output, ventilation, breathing frequency, and tidal volume were recorded.

RESULTS

PWS had slightly higher oxygen uptake (L/min) at 3.2 km/h [0.65 (0.46-1.01) vs 0.49 (0.34-0.83)] and at 4.8 km/h [0.89 (0.62-1.20) vs 0.63 (0.45-0.97)] than NW. PWS had higher ventilation (L/min) at 3.2 km/h [16.2 (13.0-26.5) vs 11.5 (8.4-17.5)], at 4.0 km/h [16.4 (13.9-27.9) vs 12.7 (10.3-19.5)], and at 4.8 km/h [19.7 (17.4-31.8) vs 15.2 (9.5-21.6)] than NW. PWS had greater breathing frequency (breaths/min) at 3.2 km/h [38 (29-53) vs 29 (22-35)], at 4.0 km/h [39 (29-58) vs 29 (23-39)], and at 4.8 km/h [39 (33-58) vs 32 (23-42)], but similar tidal volume and ventilation/carbon dioxide output to NW.

CONCLUSION

PWS did not show impaired ventilatory responses to exercise. Hyperventilation in PWS may relate to excessive neural stimulation and metabolic cost.

Orchidopexy in children with Prader-Willi syndrome: Results of a long-term follow-up study

INTRODUCTION

Prader-Willi syndrome (PWS) is a rare (1:20.000) genetic condition affecting both males and females. Among other features, in boys, the syndrome is characterized by cryptorchidism in 86-100% of cases, hypogonadism, delayed puberty and infertility. The aim of the present study is to appraise the results of orchidopexy in this selected population of children.

STUDY DESIGN

A follow-up study of children with PWS treated for undescended testes at a single institution over a 20-year period was performed. Patients were identified from a National PWS registry and reviewed at a special follow-up clinic. Data were collected from electronic and hard copies records and reported as median (range).

RESULTS

Thirty-three children (1-17 years) were identified. Co-morbidities were present in 22 (66%) and 15 (45%) were on growth-hormone therapy. Six patients (19%) had normal testes palpable in the scrotum; twenty-seven (81%) had undescended testes and required orchidopexy. Thirteen (48%) underwent a bilateral procedure for a total of 40 procedures. A 2-stage Fowler-Stephens orchidopexy was required in 2 (7%) testes. At surgery hypotrophic testes were documented in 6 (22%) patients. Age at orchidopexy was 1.4 years (0.5-5.5). Age at FU was 7.2 years (1.7-17). Length of follow-up is 3.5 years (0.4-14). At follow-up 16 (40%) testes were of normal size and palpable in the scrotum; 7 (17.5%) testes required redo-orchidopexy. All patients (6/33) over 16 years of age that had testosterone levels tested had values below normal limits after successful orchidopexy.

CONCLUSIONS

This study evaluates the results of orchidopexy in a large population of children with PWS. At follow-up, only 40% of testes were of normal size and in the scrotum. This information should be taken into consideration for patients' management and pre-operative parents' counseling.

Pilot study: Sensory integration processing disorders in children with optic nerve hypoplasia spectrum

This study aimed to explore the sensory processing profiles of children with the spectrum of optic nerve hypoplasia (ONH). Caregivers completed the Short Sensory Profile (SSP), the Social Communication Questionnaire (SCQ), and the Vineland Adaptive Behaviour Scale (VABS) interview. The study demonstrated that children with ONH present with sensory integration dysfunction (SID), in their intact senses, and that autistic spectrum condition (ASC) was the best predictor of SID, rather than visual loss, or level of intellectual disability in these children. The results indicate that assessment and monitoring of SID in children with ONH is crucial.

Obesity management in Prader-Willi syndrome: current perspectives

Prader-Willi syndrome (PWS) is a complex multisystem disorder due to the absent expression of the paternally active genes in the PWS critical region on chromosome 15 (15q11.2-q13). The syndrome is considered the most common genetic cause of obesity, occurring in 1:10,000-1:30,000 live births. Its main characteristics include neonatal hypotonia, poor feeding, and lack of appetite in infancy, followed by weight gain, lack of satiety, and uncontrolled appetite, frequently after the age of 2-3 years. The clinical picture includes short stature, multiple endocrine abnormalities (hypogonadism, growth hormone/insulin-like growth factor-I axis dysfunction, hypothyroidism, central adrenal insufficiency), dysmorphic features, scoliosis, osteoporosis, mental retardation, and behavioral and psychiatric problems. Subjects with PWS will become severely obese unless their food intake is strictly controlled. Constant and obsessive food seeking behavior can make life very difficult for both the family and caretakers. Prevention of obesity is mandatory in these patients from the first years of life, because once obesity develops it is difficult to maintain the control of food intake. In fact, PWS subjects die prematurely from complications conventionally related to obesity, including diabetes mellitus, metabolic syndrome, sleep apnea, respiratory insufficiency, and cardiovascular disease. The mechanisms underlying hyperphagia in PWS are not completely known, and to date no drugs have proven their efficacy in controlling appetite. Consequently, dietary restriction, physical activity, and behavior management are fundamental in the prevention and management of obesity in PWS. In spite of all available therapeutic tools, however, successful weight loss and maintenance are hardly accomplished. In this context, clinical trials with new drugs have been initiated in order to find new possibilities of a therapy for obesity in these patients. The preliminary results of these studies seem to be encouraging. On the other hand, until well-proven medical treatments are available, bariatric surgery can be taken into consideration, especially in PWS patients with life-threatening comorbidities.

Severe Short Stature in an Adolescent Male with Prader-Willi Syndrome and Congenital Adrenal Hyperplasia: A Therapeutic Conundrum

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency results in excess androgen production which can lead to early epiphyseal fusion and short stature. Prader-Willi syndrome (PWS) is a genetic disorder resulting from a defect on chromosome 15 due to paternal deletion, maternal uniparental disomy, or imprinting defect. Ninety percent of patients with PWS have short stature. In this article we report a patient with simple-virilizing CAH and PWS who was overtreated with glucocorticoids for CAH and not supplemented with growth hormone for PWS, resulting in a significantly short adult height.

Growth hormone therapy for Prader-willi syndrome: challenges and solutions

Prader-Willi syndrome (PWS) is characterized by a dysregulation of growth hormone (GH)/insulin-like growth factor I axis, as the consequence of a complex hypothalamic involvement. PWS' clinical picture seems to resemble the classic non-PWS GH deficiency (GHD), including short stature, excessive body fat, decreased muscle mass, and impaired quality of life. GH therapy is able to ameliorate the phenotypic appearance of the syndrome, as well as to improve body composition, physical strength, and cognitive level. In this regard, however, some pathophysiologic and clinical questions still remain, representing a challenge to give the most appropriate care to PWS patients. Data about the prevalence of GHD in PWS children are not unequivocal, ranging from 40% to 100%. In this context, to establish whether the presence (or not) of GHD may have a different effect on clinical course during GH therapy may be helpful. In addition, the comparison of GH effects in PWS children diagnosed as small for gestational age with those obtained in subjects born appropriate for gestational age is of potential interest for future trials. Emerging information seems to demonstrate the maintenance of beneficial effects of GH therapy in PWS subjects after adolescent years. Thus, GH retesting after achievement of final height should be taken into consideration for all PWS patients. However, it is noteworthy that GH administration exerts positive effects both in PWS adults with and without GHD. Another critical issue is to clarify whether the genotype-phenotype correlations may be relevant to specific outcome measures related to GH therapy. Moreover, progress of our understanding of the role of GH replacement and concomitant therapies on bone characteristics of PWS is required. Finally, a long-term surveillance of benefits and risks of GH therapy is strongly recommended for PWS population, since most of the current studies are uncontrolled and of short duration.

Deficits in voice and multisensory processing in patients with Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a rare neurodevelopmental and genetic disorder that is characterized by various expression of endocrine, cognitive and behavioral problems, among which a true obsession for food and a deficit of satiety that leads to hyperphagia and severe obesity. Neuropsychological studies have reported that PWS display altered social interactions with a specific weakness in interpreting social information and in responding to them, a symptom closed to that observed in autism spectrum disorders (ASD). Based on the hypothesis that atypical multisensory integration such as face and voice interactions would contribute in PWS to social impairment we investigate the abilities of PWS to process communication signals including the human voice. Patients with PWS recruited from the national reference center for PWS performed a simple detection task of stimuli presented in an uni-o or bimodal condition, as well as a voice discrimination task. Compared to control typically developing (TD) individuals, PWS present a specific deficit in discriminating human voices from environmental sounds. Further, PWS present a much lower multisensory benefits with an absence of violation of the race model indicating that multisensory information do not converge and interact prior to the initiation of the behavioral response. All the deficits observed in PWS were stronger for the subgroup of patients suffering from Uniparental Disomy, a population known to be more sensitive to ASD. Altogether, our study suggests that the deficits in social behavior observed in PWS derive at least partly from an impairment in deciphering the social information carried by voice signals, face signals, and the combination of both. In addition, our work is in agreement with the brain imaging studies revealing an alteration in PWS of the "social brain network" including the STS region involved in processing human voices.

Herlyn-Werner-Wunderlich and Prader-Willi syndromes: more than a coincidence?

A neonate with a prenatal diagnosis of left renal agenesis was born at 33 weeks gestation. A postnatal abdominal ultrasound confirmed the absence of the left kidney and revealed two non-divergent hemiuteri, consistent with the diagnosis of Herlyn-Werner-Wunderlich syndrome. During admission, significant axial hypotonia was noted, warranting additional investigations. Brain ultrasounds and MRI were normal, as were a preliminary metabolic study and comparative genomic hybridisation array. DNA methylation testing confirmed the diagnosis of Prader-Willi syndrome. The baby was discharged after 70 days, breast feeding and with modest hypotonia improvement.

Prediction of basal metabolic rate in patients with Prader-Willi syndrome

BACKGROUND/OBJECTIVES

The objective of this study was to develop new equations for predicting basal metabolic rate (BMR) in Prader-Willi syndrome (PWS) subjects and to compare their accuracy with commonly used equations developed by Lazzer (2007), Livingston (2005), Huang (2004), Nelson (1992), Mifflin (1990), Owen (1987), WHO (1985), Bernstein (1983) and Harris-Benedict (1919), using the Bland-Altman method.

SUBJECTS/METHODS

BMR was measured by indirect calorimetry and fat-free mass (FFM) and fat mass (FM) by a tetrapolar impedancemeter in 80 Caucasian PWS patients (mean body mass index: 39.1 kg/m(2); 17-50 years). Equations were derived by stepwise multiple regression analysis using a calibration group (n:50) and tested against the validation group (n:30).

RESULTS

Two new equations, based on anthropometric (BMR=body mass × 0.052+sex × 0.778-age × 0.033+2.839 (R(2)adj=0.61, s.e.=0.89 MJ per day)) or body composition (BMR=FFMx0.074+FMx0.042+sexx0.636-agex0.037+2.515 (R(2)adj=0.69, s.e.=0.82 MJ per day)), were generated. Predicted BMR (PBMR) was not significantly different from the measured BMR (<3.3%), and was accurate in 59% and 62% of patients, respectively. Nevertheless, significant magnitude bias was found for both equations (P<0.001, R(2)=0.36). The Owen (1987), Mifflin (1990), Huang (2004) and Lazzer (2007) equations showed mean differences <5% and PBMR was accurate in ~50% of patients. The Livingston (2005), WHO (1985) and Harris-Benedict (1919) equations showed a PBMR overestimation >7% and were accurate in <50% of patients. The Nelson (1992) and Bernstein (1983) equations showed a greater PBMR underestimation in >60% of subjects.

CONCLUSIONS

The new prediction equations showed significantly higher accuracy compared with equations tested, with exception of Lazzer (2007) and Livingston (2005) equations, and result in lower mean differences and lower limits of agreement compared with the equations tested.

The neurobiological drive for overeating implicated in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a genetic imprinting disorder characterized mainly by hyperphagia and early childhood obesity. Previous fMRI studies examined the activation of eating-related neural circuits in PWS patients with or without exposures to food cues and found an excessive eating motivation and a reduced inhibitory control of cognitive processing of food. However, the effective connectivity between various brain areas or neural circuitry critically implicated in both the biological and behavioral control of overeating in PWS is largely unexplored. The current study combined resting-state fMRI and Granger causality analysis (GCA) techniques to investigate interactive causal influences among key neural pathways underlying overeating in PWS. We first defined the regions of interest (ROIs) that demonstrated significant alterations of the baseline brain activity levels in children with PWS (n = 21) as compared to that of their normal siblings controls (n = 18), and then carried out GCA to characterize the region-to-region interactions among these ROIs. Our data revealed significantly enhanced causal influences from the amygdala to the hypothalamus and from both the medial prefrontal cortex and anterior cingulate cortex to the amygdala in patients with PWS (P < 0.001). These alterations offer new explanations for hypothalamic regulation of homeostatic energy intake and impairment in inhibitory control circuit. The deficits in these dual aspects may jointly contribute to the extreme hyperphagia in PWS. This study provides both a new methodological and a neurobiological perspective to aid in a better understanding of neural mechanisms underlying obesity in the general public. This article is part of a Special Issue entitled 1618.

[Genetic and neuroendocrine aspects in autism spectrum disorder]

The autism spectrum disorder (ASD) was described in 1943 and is defined as a developmental disorder that affects social interaction and communication. It is usually identified in early stages of development from 18 months of age. Currently, autism is considered a neurological disorder with a spectrum covering cases of different degrees, which is associated with genetic factors, not genetic and environmental. Among the genetic factors, various syndromes have been described that are associated with this disorder. Also, the neurobiology of autism has been studied at the genetic, neurophysiological, neurochemical and neuropathological levels. Neuroimaging techniques have shown multiple structural abnormalities in these patients. There have also been changes in the serotonergic, GABAergic, catecholaminergic and cholinergic systems related to this disorder. This paper presents an update of the information presented in the genetic and neuroendocrine aspects of autism spectrum disorder.

Growth hormone combined with child-specific motor training improves motor development in infants with Prader-Willi syndrome: a randomized controlled trial

Although severe motor problems in infants with Prader-Willi syndrome (PWS) are striking, motor development has never been studied longitudinally and the results of growth hormone (GH) treatment on motor development are contradictory. The authors studied whether GH treatment can enhance the effect of physical training on motor development in infants with PWS. Twenty-two infants were followed for two years during a randomized controlled trial. The treatment and control groups began GH after baseline or following a control period, respectively. Both groups followed a child-specific physical training program. Motor performance was measured every three months. Multi-level regression analysis revealed that motor development differed significantly between infants (p<.001), and this could be partially explained by baseline motor developmental level (p<.01). GH treatment enhanced the effects of child-specific physical training on both motor developmental rate and motor developmental potential. Moreover, this effect was more pronounced when GH treatment was initiated at a younger age.

The impact of Prader-Willi syndrome on the family's quality of life and caregiving, and the unaffected siblings' psychosocial adjustment

BACKGROUND

Prader-Willi syndrome (PWS), a complex multisystem genetic disorder, is characterised by developmental abnormalities leading to somatic and psychological symptoms. Symptoms of PWS include infantile hypotonia and failure-to-thrive, followed by life-long hyperphagia, developmental delays and moderate-to-severe behavioural problems and several physical problems that impact health. This study examined the effects of caring for a child diagnosed with PWS on the mothers and unaffected siblings. We assessed overall family functioning, the mothers' psychological health, the psychosocial and behavioural functioning of siblings, and the quality of life of siblings.

METHODS

Participants included 12 mothers and 13 siblings of a child with genetically confirmed PWS. Self-report measures administered to the mothers evaluated overall family functioning (PedsQL - Family Impact Module), the mothers' psychological health (Brief Symptom Inventory), and the mothers' perception of the sibling's quality of life (PedsQL - Parent Proxy). Self-report measures administered to the siblings evaluated their perceived quality of life (PedsQL) and symptoms of post-traumatic stress disorder (PTSD) (UCLA PTSD Index).

RESULTS

Families/mothers/siblings with children with PWS showed poorer perceived quality of life compared with general inpatient and outpatient samples of children with complex health conditions. Families/mothers/siblings with children with PWS reported difficulties in family functioning, communication problems, and an increased number of conflicts. They appeared to be experiencing significant behavioural distress symptoms, with higher than average levels of depression and feelings of isolation, anger and worry. Ninety-two per cent of the siblings indicated moderate-to-severe symptoms of PTSD. Compared with normative populations, siblings demonstrated poorer quality of life, with mothers perceiving more significant deficits in the sibling.

CONCLUSION

This study reaffirms that PWS affects the entire family system. Mothers and siblings would benefit from psychosocial support due to the multiple challenges of living with and caring for a child/young adult with PWS.

Effects of growth hormone treatment in adults with Prader-Willi syndrome

OBJECTIVE

Since limited data exist on adults with Prader-Willi syndrome (PWS) and growth hormone (GH) treatment, we report our experience on the effects of treatment for one year on body composition, physical activity, strength and energy expenditure, diet, general chemistry and endocrine data with quality of life measures.

DESIGN

We studied 11 adults with PWS (6F:5M; average age=32 yrs) over a 2 year period with GH treatment during the first year only. Electrolytes, IGF-I, glucose, thyroid, insulin, lipids, body composition, physical activity and strength, diet, energy expenditure and quality of life data were collected and analyzed statistically using linear modeling at baseline, at 12 months following GH therapy and at 24 months after treatment cessation for 12 months.

RESULTS

Total lean muscle mass was significantly increased (p<0.05) during GH treatment along with moderate-vigorous physical activity and plasma IGF-I and HDL levels, but returned to near baseline after treatment. Percent body fat decreased during the 12 months of GH treatment but increased after treatment.

CONCLUSIONS

Previously reported beneficial effects of GH treatment in children with PWS were found in our adults regarding body composition, physical activity and plasma HDL and IGF-I levels. Several beneficial effects diminished to near baseline after cessation of GH treatment for 12 months supporting the continuation of treatment in PWS into adulthood and possibly adults not previously treated during childhood.

Hyperactive hypothalamus, motivated and non-distractible chronic overeating in ADAR2 transgenic mice

ADAR2 transgenic mice misexpressing the RNA editing enzyme ADAR2 (Adenosine Deaminase that act on RNA) show characteristics of overeating and experience adult onset obesity. Behavioral patterns and brain changes related to a possible addictive overeating in these transgenic mice were explored as transgenic mice display chronic hyperphagia. ADAR2 transgenic mice were assessed in their food preference and motivation to overeat in a competing reward environment with ad lib access to a running wheel and food. Metabolic activity of brain and peripheral tissue were assessed with [(18) F] fluorodeoxyglucose positron emission tomography (FDG-PET) and RNA expression of feeding related genes, ADAR2, dopamine and opiate receptors from the hypothalamus and striatum were examined. The results indicate that ADAR2 transgenic mice exhibit, (1) a food preference for diets with higher fat content, (2) significantly increased food intake that is non-distractible in a competing reward environment, (3) significantly increased messenger RNA (mRNA) expressions of ADAR2, serotonin 2C receptor (5HT2C R), D1, D2 and mu opioid receptors and no change in corticotropin-releasing hormone mRNAs and significantly reduced ADAR2 protein expression in the hypothalamus, (4) significantly increased D1 receptor and altered bioamines with no change in ADAR2, mu opioid and D2 receptor mRNA expression in the striatum and (5) significantly greater glucose metabolism in the hypothalamus, brain stem, right hippocampus, left and right mid brain regions and suprascapular peripheral tissue than controls. These results suggest that highly motivated and goal-oriented overeating behaviors of ADAR2 transgenic mice are associated with altered feeding, reward-related mRNAs and hyperactive brain mesolimbic region.

The effect of growth hormone treatment or physical training on motor performance in Prader-Willi syndrome: a systematic review

Although motor problems in Prader-Willi syndrome (PWS) are prominent in infants, and continue into childhood and adulthood, there is little insight into the factors important for clinical management. The literature was reviewed to: (1) provide an overview of the characteristics and prevalence of motor problems and (2) evaluate the effects of growth hormone (GH) treatment and physical training on motor performance. A systematic search revealed 34 papers: 13 on motor performance; 12 on GH treatment; and nine on physical training. In infants, motor development is 30-57% of the normal reference values, and children and adults also have significant problems in skill acquisition, muscle force, cardiovascular fitness, and activity level. GH treatment positively influenced motor performance in infants, children, and adults, although not all studies demonstrated an effect. All studies on physical training demonstrated beneficial effects in PWS patients. We suggest a combination of GH treatment and physical training to be started as soon as possible, especially in infants, to improve motor development as this will positively influence general development.