Growth hormone treatment increases CO(2) response, ventilation and central inspiratory drive in children with Prader-Willi syndrome

Hypoventilation in patients with Prader-Willi syndrome across the pediatric age

OBJECTIVES

Few data on alveolar hypoventilation in Prader-Willi syndrome (PWS) are available and the respiratory follow-up of these patients is not standardized. The objectives of this study were to evaluate the prevalence of alveolar hypoventilation in children with PWS and identify potential risk factors.

STUDY DESIGN

This retrospective study included children with PWS recorded by polysomnography (PSG) with transcutaneous carbon dioxide pressure (PtcCO2) or end-tidal CO2 (ETCO2) measurements, between 2007 and 2021, in a tertiary hospital center. The primary outcome was the presence of alveolar hypoventilation defined as partial pressure of carbon dioxide (pCO2) ≥ 50 mmHg during ≥2% of total sleep time (TST) or more than five consecutive minutes.

RESULTS

Among the 57 included children (38 boys, median age 4.8 years, range 0.1-15.6, 60% treated with growth hormone [GH], 37% obese), 19 (33%) had moderate-to-severe obstructive sleep apnea syndrome (defined as obstructive apnea-hypopnea index ≥5/h) and 20 (35%) had hypoventilation. The median (range) pCO2 max was 49 mmHg (38-69). Among the children with hypoventilation, 25% were asymptomatic. Median age and GH treatment were significantly higher in children with hypoventilation compared to those without. There was no significant difference in terms of sex, BMI, obstructive or central apnea-hypopnea index between both groups.

CONCLUSION

The frequency of alveolar hypoventilation in children and adolescents with PWS is of concern and may increase with age and GH treatment. A regular screening by oximetry-capnography appears to be indicated whatever the sex, BMI, and rate of obstructive or central apneas.

Sleep Consequences of Prader-Willi Syndrome

PURPOSE OF REVIEW

This paper reviews how sleep is impacted in patients with Prader-Willi syndrome (PWS), focusing on sleep-related breathing disturbances and excessive daytime sleepiness (EDS).

RECENT FINDINGS

Hypothalamic dysfunction may underlie several aspects of the PWS phenotype. Central sleep apnea (CSA) can persist beyond infancy. Nocturnal hypoventilation is common and may occur without central or obstructive sleep apnea (OSA). Adenotonsillectomy, a mainstay of OSA treatment, may cause velopharyngeal insufficiency. Growth hormone (GH) is considered safe, but close surveillance for OSA remains important. Cardiac autonomic dysfunction occurs during slow wave sleep and may increase the risk of cardiovascular events. EDS and narcolepsy are also common. Modafinil and pitolisant are treatment options currently being studied. Sleep disorders are prevalent in individuals with PWS. Sleep-related breathing disorders present as CSA in infancy and later in life as OSA and hypoventilation. GH therapy has improved the clinical outcomes of patients with PWS, but close surveillance and treatment for OSA is recommended. EDS can persist even after sleep-related breathing disorders are treated, and some individuals may even develop narcolepsy. Early recognition and treatment of sleep-related disorders may prevent morbidity and result in improved survival of patients with PWS.

The effect of central growth hormone action on hypoxia ventilatory response in conscious mice

Growth hormone (GH)-responsive neurons regulate several homeostatic behaviors including metabolism, energy balance, arousal, and stress response. Therefore, it is possible that GH-responsive neurons play a role in other responses such as CO2/H+-dependent breathing behaviors. Here, we investigated whether central GH receptor (GHR) modulates respiratory activity in conscious unrestrained mice. First, we detected clusters of GH-responsive neurons in the tyrosine hydroxylase-expressing cells in the rostroventrolateral medulla (C1 region) and within the locus coeruleus (LC). No significant expression was detected in phox2b-expressing cells in the retrotrapezoid nucleus. Whole body plethysmography revealed a reduction in the tachypneic response to hypoxia (FiO2 = 0.08) without changing baseline breathing and the hypercapnic ventilatory response. Contrary to the physiological findings, we did not find significant differences in the number of fos-activated cells in the nucleus of the solitary tract (NTS), C1, LC and paraventricular nucleus of the hypothalamus (PVH). Our finding suggests a possible secondary role of central GH action in the tachypneic response to hypoxia in conscious mice.

Preserved Sleep for the Same Level of Respiratory Disturbance in Children with Prader-Willi Syndrome

Debate remains as to how to balance the use of recombinant human growth hormone (rhGH) as an important treatment in Prader-Willi syndrome (PWS) with its potential role in obstructive sleep apnea. This single-center, retrospective study assessed differences in overnight polysomnography results between children with and without PWS and changes in respiratory parameters before and after the initiation of rhGH treatment in those with PWS. Compared with age-, sex-, and body-mass-index-matched controls (n = 87), children with PWS (n = 29) had longer total sleep time (434 ± 72 vs. 365 ± 116 min; p < 0.01), higher sleep efficiency (86 ± 7 vs. 78 ± 15%; p < 0.05), and lower arousal events (8.1 ± 4.5 vs. 13.0 ± 8.9 events/h; p < 0.05). Mean oxygen saturation was lower in PWS children (94.3 ± 6.0 vs. 96.0 ± 2.0%; p < 0.05), with no other differences in respiratory parameters between groups. Eleven children with PWS (38%) met the criteria for further analyses of the impact of rhGH; polysomnography parameters did not change with treatment. Compared with other children undergoing polysomnography, children with PWS had more favorable markers of sleep continuity and lower oxygen saturation for the same level of respiratory disturbance. rhGH administration was not associated with changes in respiratory parameters in PWS.

Diagnosis and management of sleep disorders in Prader-Willi syndrome

Clinical experience and a growing body of evidence suggest that sleep disturbances are common in people with Prader-Willi syndrome (PWS). PWS is a rare neuroendocrine disorder characterized by early hypotonia and feeding difficulties; developmental delays; endocrinopathies; and behavioral concerns, especially rigidity, anxiety, and behavioral outbursts. PWS is also characterized by decreased resting energy expenditure and transition to hyperphagia and obesity. We propose that, for many people with PWS, clinical diagnosis and management of sleep disorders is an unmet need. We present current information to suggest disordered sleep is a significant burden for individuals with PWS and often overlooked. While central and obstructive sleep apnea are more widely recognized in PWS, other sleep disorders have increasingly gained recognition, including hypersomnia, narcolepsy-like phenotypes, and insomnia. Sleep disorders can impact behavior, cognition, and quality of life and health for individuals with PWS. Our goal is to bring sleep disorders to the forefront of therapeutic intervention for patients with PWS. This paper presents a review of the literature and recommendations for clinical practice based on published research and our clinical experience as sleep specialists, geneticists, psychiatrists, pediatricians, otolaryngologists, and pulmonologists with extensive experience with this patient population. We recommend that management of sleep be considered an integral part of successful medical management of PWS. Further research concerning sleep problems in PWS is urgently needed to develop best practices and work toward a consensus statement for medical management to meet the needs of people with PWS.

CITATION

Duis J, Pullen LC, Picone M, et al. Diagnosis and management of sleep disorders in Prader-Willi syndrome. J Clin Sleep Med. 2022;18(6):1687-1696.

Sleep-disordered breathing in Australian children with Prader-Willi syndrome following initiation of growth hormone therapy

AIM

In children with Prader-Willi syndrome (PWS), growth hormone (GH) improves height and body composition; however, may be associated with worsening sleep-disordered breathing (SDB). Some studies have reported less SDB after GH initiation, but follow-up with polysomnography is still advised in most clinical guidelines.

METHODS

This retrospective, multicentre study, included children with PWS treated with GH at seven PWS treatment centres in Australia over the last 18 years. A paired analysis comparing polysomnographic measures of central and obstructive SDB in the same child, before and after GH initiation was performed with Wilcoxon signed-rank test. The proportion of children who developed moderate/severe obstructive sleep apnoea (OSA) was calculated with their binomial confidence intervals.

RESULTS

We included 112 patients with available paired data. The median age at start of GH was 1.9 years (range 0.1-13.5 years). Median obstructive apnoea hypopnoea index (AHI) at baseline was 0.43/h (range 0-32.9); 35% had an obstructive AHI above 1.0/h. Follow-up polysomnography within 2 years after the start of GH was available in 94 children who did not receive OSA treatment. After GH initiation, there was no change in central AHI. The median obstructive AHI did not increase significantly (P = 0.13), but 12 children (13%, CI_95% 7-21%) developed moderate/severe OSA, with clinical management implications.

CONCLUSIONS

Our findings of a worsening of OSA severity in 13% of children with PWS support current advice to perform polysomnography after GH initiation. Early identification of worsening OSA may prevent severe sequelae in a subgroup of children.

Sleep-disordered breathing in school-aged children with Prader-Willi Syndrome

STUDY OBJECTIVES

Studies of sleep-disordered breathing (SDB) in children with Prader-Willi syndrome (PWS) have focused on early childhood and growth hormone (GH)-naïve children, but little is known about older children, including those on long term GH therapy. This study aimed to describe the nature and prevalence of SDB in school-aged children with PWS in the growth hormone era.

METHODS

This retrospective single-center chart review included children aged 6-18 years with PWS who had overnight polysomnography not involving respiratory support over five years (2012-2017). The main outcome measures were the presence of obstructive sleep apnea, central sleep apnea or hypoventilation defined by an elevated PCO₂ as per standard pediatric criteria.

RESULTS

Seventeen children (8 male, median age 11.6y, range 6.6-16.1y) were included. Fifteen demonstrated SDB of different types: central sleep apnea (18%), obstructive sleep apnea (24%), both obstructive and central sleep apnea (29%), or hypoventilation without obstructive or central sleep apnea (18%). Twelve (71%) children had evidence of hypoventilation. Those with hypoventilation had a higher central apnea-hypopnea index (AHI) but no difference in the obstructive AHI, age, sex, growth parameters, or the presence of scoliosis or sleep-related symptoms compared to those without hypoventilation.

CONCLUSIONS

Sleep-related hypoventilation is common in school-aged children with PWS. The presence of central sleep apnea, including the quantification of central hypopneas, but not obstructive sleep apnea or clinical factors predicted the presence of hypoventilation. Long-term polysomnography surveillance in children with PWS should include identification of central hypopneas and measurement of continuous pCO₂.

Sleep-disordered breathing and genetic findings in children with Prader-Willi syndrome in China

Background

Sleep-related breathing disorders are common in individuals with Prader-Willi syndrome (PWS), and can include hypersomnolence and obstructive sleep apnea, as well as central sleep breathing abnormalities that are present from infancy. Here we describe the sleep-disordered breathing (SDB) and genetic findings in patients with PWS in China.

Methods

In all, 48 patients confirmed by genetic tests were enrolled, 32 were under 2 years of age and 16 were older children. There were 37 (77.1%) patients with paternal 15q11-13 deletions, 11 (22.9%) patients with maternal uniparental disomy (mUPD), and no patients with imprinting defect (ID).

Results

Compared with infants, a significantly higher proportion of older children with PWS were overweight or obese (15/16 children vs. 4/32 infants) and children had a higher serum level of free thyroxine (FT4) (0.9±0.2 vs. 0.7±0.7) and thyroxine (T4) (9.0±2.5 vs. 7.5±1.7). Age was correlated significantly with body mass index (BMI), T4, and FT4 (r=0.626, P=0.000; r=0.426, respectively). Overall, 42 of 48 (87.5%) patients had sleep apnea on polysomnography (PSG). Infants, when compared with older children, were more likely to experience central sleep apnea (71.8% vs. 25%). In infants, there were no significant differences in the prevalence of SDB between the deletion group and the mUPD group.

Conclusions

Being overweight or obese was more common in older children with PWS. Compared with infants, a higher proportion children were overweight or obese and had higher serum levels of FT4 and T4. The prevalence of SDB was high in those with PWS, and central sleep apnea was found to be prevalent in infants. The pattern of SDB in infants with PWS was not significantly associated with the genotypes.

Sleep disordered breathing in Silver-Russell syndrome patients: a new outcome

OBJECTIVE

Imprinting disorders (ID), such as Prader-Willi syndrome (PWS), are associated with sleep-disordered breathing (SDB). No data are available for Silver-Russell syndrome (SRS), another ID that shares clinical features with PWS, although many patients describe excessive daytime sleepiness, disturbed sleep, and snoring. The aim of this study was to characterize sleep in children with SRS and to evaluate the impact of recombinant growth hormone (rGH) therapy.

METHODS

We performed a retrospective analysis of sleep recordings in 40 patients with molecularly proven SRS (methylation anomaly in 11p15 [n = 32] or maternal uniparental disomy of chromosome 7 [n = 16]). Sleep recordings were either by means of polygraphy or polysomnography (PSG) (n = 16). A total of 34 patients received rGH therapy.

RESULTS

We collected 61 sleep recordings. The mean apnea-hypopnea index (AHI) was 3.4 events/h (0-12.4), with a mean central AHI of 0.5 events/h (0-2.4). SDB was identified in 73.8% (n = 45) of the recordings and was severe in 4.9%. SDB was present in 86.4% of patients before rGH therapy and was severe in 13.6%. AHI worsened for 5 of 12 patients with sleep recordings before and after rGH therapy initiation, reaching mild impairment. The mean rGH dose was 32.3 μg/kg/(12.9-51.4), with a mean insulin-like growth factor 1 plasma level of 1.7 SDS (-1.9 to 6.6).

CONCLUSION

Most patients with SRS present with SDB with an obstructive profile, possibly explained by narrowing of the airways and lymphoid organ hypertrophy. We recommend systematic ear-nose-throat evaluation of SRS patients and PSG if there are clinical anomalies, preferably before initiating rGH therapy, to monitor and adapt the management of patients with SDB.

Sleep-related breathing disorders in young adults with Prader-Willi syndrome: a placebo-controlled, cross-over GH trial

CONTEXT

Sleep-related breathing disorders (SRBD) are common in people with Prader-Willi syndrome (PWS). Young adults with PWS benefit from GH continuation after adult height by maintaining the improved body composition obtained during childhood. There are, however, no studies about the effects of GH on SRBD in young adults with PWS who were treated with GH during childhood.

OBJECTIVE

To investigate the effects of GH versus placebo on SRBD in young adults with PWS who were treated with GH during childhood and had attained adult height.

DESIGN

2-year, randomized, double-blind, placebo-controlled, cross-over GH-study in 27 young adults with PWS, stratified for gender and BMI.

SETTING

Dutch PWS Reference Center.

INTERVENTION

Cross-over intervention with GH (0.67 mg/m2/day) and placebo, both during one year.

MAIN OUTCOME MEASURES

Apnea hypopnea index (AHI), obstructive apnea index (OAI), central apnea index (CAI), measured by polysomnography.

RESULTS

Compared to placebo, GH treatment did not increase AHI, CAI or OAI (p>0.35). The effect of GH versus placebo was neither different between men and women, nor between patients with a deletion or mUPD/ICD. After 2 years, there was no difference in AHI, CAI or OAI compared to baseline (p>0.18). Two patients (7%) fulfilled the criteria of obstructive sleep apnea (OSA), regardless of GH or placebo.

CONCLUSIONS

GH compared to placebo does not cause a significant increase in AHI, CAI or OAI in adults with PWS who were treated with GH during childhood and have attained adult height. Our findings are reassuring and prove that GH can be safely administered.

Respiratory Complications in Children with Prader Willi Syndrome

Prader Willi syndrome, resulting from the partial deletion or lack of expression of a region of genes on the paternal chromosome 15, has a number of phenotypic features which predispose affected patients to ventilatory problems. These include generalised hypotonia, abnormal arousal and ventilatory responses to hypoxia and hypercapnia, scoliosis and frequently, obesity. The spectrum of the resulting respiratory complications thus runs from sleep disordered breathing, to aspiration and respiratory functional impairment. While the use of growth hormone, in conjunction with multidisciplinary clinical management, is currently the cornerstone of clinical care of these patients, concerns have been raised following reports of sudden death shortly after growth hormone initiation. This review summarizes the respiratory complications commonly seen and draws together the published literature on the impact of growth hormone in relation to various respiratory parameters, aiming to provide the reader with the necessary information to manage these patients as safely as possible.

Sexual dimorphism of cardiopulmonary regulation in the arcuate nucleus of the hypothalamus

The arcuate nucleus of the hypothalamus (ANH) interacts with other hypothalamic nuclei, forebrain regions, and downstream brain sites to affect autonomic nervous system outflow, energy balance, temperature regulation, sleep, arousal, neuroendocrine function, reproduction, and cardiopulmonary regulation. Compared to studies of other ANH functions, how the ANH regulates cardiopulmonary function is less understood. Importantly, the ANH exhibits structural and functional sexually dimorphic characteristics and contains numerous neuroactive substances and receptors including leptin, neuropeptide Y, glutamate, acetylcholine, endorphins, orexin, kisspeptin, insulin, Agouti-related protein, cocaine and amphetamine-regulated transcript, dopamine, somatostatin, components of renin-angiotensin system and gamma amino butyric acid that modulate physiological functions. Moreover, several clinically relevant disorders are associated with ANH ventilatory control dysfunction. This review highlights how ANH neurotransmitter systems and receptors modulate breathing differently in male and female rodents. Results highlight the significance of the ANH in cardiopulmonary regulation. The paucity of studies in this area that will hopefully spark investigations of sexually dimorphic ANH-modulation of breathing.

Disorders of Sleep and Ventilatory Control in Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is an imprinted genetic disorder conferred by loss of paternal gene expression from chromosome 15q11.2-q13. Individuals with PWS have impairments in ventilatory control and are predisposed toward sleep disordered breathing due to a combination of characteristic craniofacial features, obesity, hypotonia, and hypothalamic dysfunction. Children with PWS progress from failure to thrive during infancy to hyperphagia and morbid obesity during later childhood and onward. Similarly, the phenotype of sleep disordered breathing in PWS patients also evolves over time from predominantly central sleep apnea in infants to obstructive sleep apnea (OSA) in older children. Behavioral difficulties are common and may make establishing effective therapy with continuous positive airway pressure (CPAP) more challenging when OSA persists after adenotonsillectomy. Excessive daytime sleepiness (EDS) is also common in patients with PWS and may continue after OSA is effectively treated. We describe here the characteristic ventilatory control deficits, sleep disordered breathing, and excessive daytime sleepiness seen in individuals with PWS. We review respiratory issues that may contribute to sudden death events in PWS patients during sleep and wakefulness. We also discuss therapeutic options for treating sleep disordered breathing including adenotonsillectomy, weight loss, and CPAP. Lastly, we discuss the benefits and safety considerations related to growth hormone therapy.

Somatropin therapy for children with prader-willi syndrome : guidelines for use

Prader-Willi syndrome is a neurogenetic disorder that occurs due to the lack of a paternally expressed gene or genes on chromosome 15q11-q13. Many of the symptoms present in Prader-Willi syndrome are due to a hypothalamic-pituitary dysfunction. The main characteristics are muscular hypotonia, delayed psychomotor development, insatiable appetite resulting in overweight if a diet is not maintained, compromised growth and puberty resulting in a short final height and incomplete sexual development, respiratory disturbances, and dysmorphic features. Individuals with Prader-Willi syndrome have compromised growth and abnormal body composition with increased fat mass, decreased lean body mass, and low bone density, resembling a growth hormone-deficient status. Somatropin treatment has a beneficial effect on growth with increased final height and an improvement in and maintenance of body composition, as well as a beneficial effect on respiratory functions. Before initiating somatropin therapy, weight should be kept at an appropriate level, and polysomnography, as well as an otorhinolaryngologic examination should be performed. During somatropin therapy, carbohydrate metabolism and the development of scoliosis should be monitored, as well as bodyweight.A comprehensive team to manage the various components of medical, psychologic, and sociologic care is required for individuals with Prader-Willi syndrome.

Prader-Willi syndrome: a review of clinical, genetic, and endocrine findings

INTRODUCTION

Prader-Willi syndrome (PWS) is a multisystemic complex genetic disorder caused by lack of expression of genes on the paternally inherited chromosome 15q11.2-q13 region. There are three main genetic subtypes in PWS: paternal 15q11-q13 deletion (65-75 % of cases), maternal uniparental disomy 15 (20-30 % of cases), and imprinting defect (1-3 %). DNA methylation analysis is the only technique that will diagnose PWS in all three molecular genetic classes and differentiate PWS from Angelman syndrome. Clinical manifestations change with age with hypotonia and a poor suck resulting in failure to thrive during infancy. As the individual ages, other features such as short stature, food seeking with excessive weight gain, developmental delay, cognitive disability and behavioral problems become evident. The phenotype is likely due to hypothalamic dysfunction, which is responsible for hyperphagia, temperature instability, high pain threshold, hypersomnia and multiple endocrine abnormalities including growth hormone and thyroid-stimulating hormone deficiencies, hypogonadism and central adrenal insufficiency. Obesity and its complications are the major causes of morbidity and mortality in PWS.

METHODS

An extensive review of the literature was performed and interpreted within the context of clinical practice and frequently asked questions from referring physicians and families to include the current status of the cause and diagnosis of the clinical, genetics and endocrine findings in PWS.

CONCLUSIONS

Updated information regarding the early diagnosis and management of individuals with Prader-Willi syndrome is important for all physicians and will be helpful in anticipating and managing or modifying complications associated with this rare obesity-related disorder.

Syndromic disorders with short stature

Short stature is one of the major components of many dysmorphic syndromes. Growth failure may be due to a wide variety of mechanisms, either related to the growth hormone (GH)/insulin-like growth factor axis or to underlying unknown pathologies. In this review, the relatively more frequently seen syndromes with short stature (Noonan syndrome, Prader-Willi syndrome, Silver-Russell syndrome and Aarskog-Scott syndrome) were discussed. These disorders are associated with a number of endocrinopathies, as well as with developmental, systemic and behavioral issues. At present, GH therapy is used in most syndromic disorders, although long-term studies evaluating this treatment are insufficient and some controversies exist with regard to GH dose, optimal age to begin therapy and adverse effects. Before starting GH treatment, patients with syndromic disorders should be evaluated extensively.

Genetic diseases: congenital central hypoventilation, Rett, and Prader-Willi syndromes

The present review summarizes current knowledge on three rare genetic disorders of respiratory control, congenital central hypoventilation syndrome (CCHS), Rett syndrome (RTT), and Prader-Willi syndrome (PWS). CCHS is characterized by lack of ventilatory chemosensitivity caused by PHOX2B gene abnormalities consisting mainly of alanine expansions. RTT is associated with episodes of tachypneic and irregular breathing intermixed with breathholds and apneas and is caused by mutations in the X-linked MECP2 gene encoding methyl-CpG-binding protein. PWS manifests as sleep-disordered breathing with apneas and episodes of hypoventilation and is caused by the loss of a group of paternally inherited genes on chromosome 15. CCHS is the most specific disorder of respiratory control, whereas the breathing disorders in RTT and PWS are components of a more general developmental disorder. The main clinical features of these three disorders are reviewed with special emphasis on the associated brain abnormalities. In all three syndromes, disease-causing genetic defects have been identified, allowing the development of genetically engineered mouse models. New directions for future therapies based on these models or, in some cases, on clinical experience are delineated. Studies of CCHS, RTT, and PWS extend our knowledge of the molecular and cellular aspects of respiratory rhythm generation and suggest possible pharmacological approaches to respiratory control disorders. This knowledge is relevant for the clinical management of many respiratory disorders that are far more prevalent than the rare diseases discussed here.

Growth hormone therapy and respiratory disorders: long-term follow-up in PWS children

CONTEXT

Adenotonsillar tissue hypertrophy and obstructive sleep apnea have been reported during short-term GH treatment in children with Prader-Willi syndrome (PWS).

OBJECTIVE

We conducted an observational study to evaluate the effects of long-term GH therapy on sleep-disordered breathing and adenotonsillar hypertrophy in children with PWS.

DESIGN

This was a longitudinal observational study.

PATIENTS AND METHODS

We evaluated 75 children with genetically confirmed PWS, of whom 50 fulfilled the criteria and were admitted to our study. The patients were evaluated before treatment (t0), after 6 weeks (t1), after 6 months (t2), after 12 months (t3), and yearly (t4-t6) thereafter, for up to 4 years of GH therapy. The central apnea index, obstructive apnea hypopnea index (OAHI), respiratory disturbance index, and minimal blood oxygen saturation were evaluated overnight using polysomnography. We evaluated the adenotonsillar size using a flexible fiberoptic endoscope.

RESULTS

The percentage of patients with an OAHI of >1 increased from 3 to 22, 36, and 38 at t1, t4, and t6, respectively (χ(2) = 12.2; P < .05). We observed a decrease in the respiratory disturbance index from 1.4 (t0) to 0.8 (t3) (P < .05) and the central apnea index from 1.2 (t0) to 0.1 (t4) (P < .0001). We had to temporarily suspend treatment for 3 patients at t1, t4, and t5 because of severe obstructive sleep apnea. The percentage of patients with severe adenotonsillar hypertrophy was significantly higher at t4 and t5 than at t0. The OAHI directly correlated with the adenoid size (adjusted for age) (P < .01) but not with the tonsil size and IGF-1 levels.

CONCLUSION

Long-term GH treatment in patients with PWS is safe; however, we recommend annual polysomnography and adenotonsillar evaluation.

Long-term effects of recombinant human growth hormone therapy in children with Prader-Willi syndrome

PURPOSE OF REVIEW

Recombinant human growth hormone (hGH) therapy in children with Prader-Willi syndrome (PWS) improves linear growth, body composition, physical strength and agility, and other metabolic parameters. These benefits must be weighed against potential adverse effects, including rare occurrences of sudden death. This review summarizes recent evidence important to a benefit-risk analysis of hGH use in children with PWS.

RECENT FINDINGS

Studies consistently show that hGH improves stature, body composition, fat percentage and distribution, and other metabolic markers in children with PWS. Preliminary reports of improved cognitive development during hGH have also emerged. Scoliosis progression is influenced by growth rate, but frequency of occurrence and severity are not increased by hGH exposure. PWS genotype does not appear to affect response to hGH. Concerns about hGH-associated sudden death persist, but recent studies show either absence of change in sleep-disordered breathing or improved sleep cardiovascular function during hGH therapy.

SUMMARY

Recent studies confirm and expand reported benefits of hGH therapy in children with PWS, including a possible salutary role in cognitive development. These findings support previous assertions that hGH can reduce morbidity and improve function in children with PWS, and suggest that potential risks of such treatment are favorably balanced by its benefits.

GrowthHormone Research Society workshop summary: consensus guidelines for recombinant human growth hormone therapy in Prader-Willi syndrome

CONTEXT

Recombinant human GH (rhGH) therapy in Prader-Willi syndrome (PWS) has been used by the medical community and advocated by parental support groups since its approval in the United States in 2000 and in Europe in 2001. Its use in PWS represents a unique therapeutic challenge that includes treating individuals with cognitive disability, varied therapeutic goals that are not focused exclusively on increased height, and concerns about potential life-threatening adverse events.

OBJECTIVE

The aim of the study was to formulate recommendations for the use of rhGH in children and adult patients with PWS.

EVIDENCE

We performed a systematic review of the clinical evidence in the pediatric population, including randomized controlled trials, comparative observational studies, and long-term studies (>3.5 y). Adult studies included randomized controlled trials of rhGH treatment for ≥ 6 months and uncontrolled trials. Safety data were obtained from case reports, clinical trials, and pharmaceutical registries.

METHODOLOGY

Forty-three international experts and stakeholders followed clinical practice guideline development recommendations outlined by the AGREE Collaboration (www.agreetrust.org). Evidence was synthesized and graded using a comprehensive multicriteria methodology (EVIDEM) (http://bit.ly.PWGHIN).

CONCLUSIONS

Following a multidisciplinary evaluation, preferably by experts, rhGH treatment should be considered for patients with genetically confirmed PWS in conjunction with dietary, environmental, and lifestyle interventions. Cognitive impairment should not be a barrier to treatment, and informed consent/assent should include benefit/risk information. Exclusion criteria should include severe obesity, uncontrolled diabetes mellitus, untreated severe obstructive sleep apnea, active cancer, or psychosis. Clinical outcome priorities should vary depending upon age and the presence of physical, mental, and social disability, and treatment should be continued for as long as demonstrated benefits outweigh the risks.

Are sleep studies helpful in children with Prader-Willi syndrome prior to commencement of growth hormone therapy?

AIMS

To examine sleep study findings in children with Prader-Willi syndrome (PWS) referred for polysomnography (PSG) before commencement of growth hormone (GH) and to evaluate the impact of sleep testing on treatment decisions.

METHODS

The sleep unit database was used to identify all cases over an 8-year period (2003-2011). Standard overnight PSG was performed in the sleep laboratory. Obstructive sleep apnoea (OSA) was defined by an obstructive apnoea-hypopnoea index >1/h. Age, symptoms of OSA, tonsillar size and body mass index (BMI) Z-score were obtained through chart review.

RESULTS

OSA was diagnosed in 15 of 34 (44%) cases identified. Those with OSA were significantly older (P = 0.009) and more likely to have enlarged tonsils (P = 0.05) than those without OSA. There was no difference in BMI Z-score or the presence of symptoms of OSA. GH was deferred in 13 (38%) pending treatment for OSA.

CONCLUSIONS

OSA was frequently present in children with PWS referred simply to meet the requirement for PSG before starting GH. OSA was more likely in older children and those with enlarged tonsils. GH treatment was deferred in 38% of cases. This study supports routine performance of PSG prior to GH, regardless of clinical history.

The effect of growth hormone on sleep-related cardio-respiratory control in Prader-Willi syndrome

AIM

To evaluate the effects of growth hormone (GH) treatment on control of breathing, heart rate and blood pressure during sleep in Prader-Willi Syndrome (PWS).

STUDY DESIGN

In a prospective clinical case series study, sixteen consecutive PWS patients (median age 16 months at enrolment) were followed-up 6 months (2-32 months) after commencing GH treatment. We compared heart rate (HR), Pulse Transit Time (PTT; an index of blood pressure, BP) and ventilatory responses to standard chemostimuli (4% CO(2) and 100% O(2)) during quiet sleep prior to and after commencing GH treatment.

RESULTS

Growth hormone treatment increased arterial oxygenation during sleep but did not significantly improve breathing stability (apnoea-hypopnoea index remained unchanged). GH treatment did not alter ventilatory, HR and PTT chemoreceptor-mediated responsiveness (p = 0.23-0.97) but did significantly improve the coupling between and HR and PTT, indicating that HR and BP rose (or fell) in parallel after but not before GH therapy (p = 0.01).

CONCLUSION

Growth hormone treatment improves arterial oxygenation and cardiovascular function during sleep; these changes are not owing to improved (stronger) chemoreflex-mediated autonomic drive.

Growth hormone treatment for two years is safe and effective in adults with Prader-Willi syndrome

OBJECTIVE

Prader-Willi syndrome (PWS) shares similarities with the growth hormone (GH) deficiency syndrome in regards to reduced lean body mass and increased fat mass and several short-term trials with GH treatment have demonstrated beneficial effects on body composition. The aim of the present study was to evaluate the effects and safety of two years of GH therapy in adults with PWS.

DESIGN

Forty-three adults (24 women) with genetically verified PWS were included. Blood samples, body composition as measured by computed tomography (CT) and dual-energy x-ray absorptiometry (DXA) were performed at baseline and during two years of continued GH treatment.

RESULTS

Thirty-nine patients completed treatment for two years. The GH dosage averaged 0.61 mg/day (range 0.2-1.6). Based upon CT, body composition improved at two years; thigh muscle volume increased 6.7 mL (3.7 to 9.7; P<0.001) whereas abdominal subcutaneous fat volume decreased by 53.3 mL (13.8 to 92.9; P=0.01). By DXA, lean body mass improved 2.8 kg (1.9 to 3.6; P<0.001), whereas fat mass decreased by 3.0 kg (1.1 to 4.8; P=0.003). Lung function as evaluated by peak expiratory flow increased 12% (p<0.001) - indicating improved muscle function. Adverse effects were few. Fifteen out of 39 patients had diabetes (DM; n=4) or impaired glucose tolerance (IGT; n=11) prior to GH treatment. Among the 11 patients with IGT, three reverted to normal glucose tolerance, while three progressed to overt DM at two years of GH treatment.

CONCLUSION

The known beneficial effects of GH treatment upon body composition in PWS are maintained during two years continuous treatment. With appropriate control, GH is a safe treatment option in adults with PWS.

Clinical report—health supervision for children with Prader-Willi syndrome

This set of guidelines was designed to assist the pediatrician in caring for children with Prader-Willi syndrome diagnosed by clinical features and confirmed by molecular testing. Prader-Willi syndrome provides an excellent example of how early diagnosis and management can improve the long-term outcome for some genetic disorders.

Longitudinal association between growth hormone therapy and obstructive sleep apnea in a child with Prader-Willi syndrome

CONTEXT

Descriptions of the development of symptoms of upper airway obstruction and sudden death of children with Prader-Willi Syndrome (PWS) while on GH therapy have led to concern about GH contributing to obstructive sleep apnea (OSA), especially early in treatment. However, two studies using monitoring with polysomnography (PSG) have not shown deterioration in OSA after 6 wk on GH, except as related to upper respiratory tract infections.

OBJECTIVE

The aim was to describe the evolution of OSA in a girl with PWS on GH treatment in order to highlight important aspects of long-term clinical monitoring for patients with PWS on GH treatment. PATIENT AND RESEARCH DESIGN: GH was commenced when the patient was 2.9 yr of age. PSG was performed at baseline and 7 wk after commencing GH, plus at intervals throughout treatment based on symptoms of OSA.

INTERVENTION

GH was given at doses ranging from 4.2 to 4.7 mg/m(2) · wk over a period of 3 yr.

MAIN OUTCOME MEASURE

OSA was quantified by PSG.

RESULTS

OSA was not present at baseline or after 7 wk on GH but developed after 6 months, following a small increase in GH dose. Cessation of GH was accompanied by resolution of OSA. GH was restarted 2 yr later, again associated with the development of OSA that resolved after cessation of GH.

CONCLUSION

This case highlights that OSA may develop late in GH treatment. Children should be monitored for the symptoms of OSA throughout GH treatment, and PSG should be repeated if symptoms develop.

Long-term effects of growth hormone therapy on patients with Prader-Willi syndrome

AIM

To assess the effects of recombinant human growth hormone (rhGH) treatment in children with Prader-Willi syndrome.

DESIGN

A 1-year study and an observational follow-up visit 10 years later.

METHODS

In 20 patients with Prader-Willi syndrome (PWS): clinical assessment, laboratory tests, body composition analysis by dual energy X-ray absorptiometry, sleep polygraphy, health-related quality of life assessed by 16D.

RESULTS

Only two patients had normal growth hormone secretion at baseline. All patients were significantly shorter than their expected heights, but experienced catch-up growth during growth hormone treatment. At follow-up, 13 patients had reached adult heights and were markedly taller than historical controls. The cumulative dose of rhGH over 10 years correlated inversely with the total body fat percentage (p = 0.033). However, patients remained severely obese at 10 years. Sleep polygraphy was abnormal in more than half of the patients. Health-related quality of life of the patients remained substantially below that of normal population.

CONCLUSION

Growth hormone markedly improved adult height in subjects with PWS when compared to historical data. The cumulative dose of growth hormone correlated with reduction in body fat; nevertheless, patients remained severely obese.

Clinical management of behavioral characteristics of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder caused by an abnormality on the long arm of chromosome 15 (q11-q13) that results in a host of phenotypic characteristics, dominated primarily by hyperphagia and insatiable appetite. Characteristic behavioral disturbances in PWS include excessive interest in food, skin picking, difficulty with a change in routine, temper tantrums, obsessive and compulsive behaviors, and mood fluctuations. Individuals with PWS typically have intellectual disabilities (borderline to mild/moderate mental retardation) and exhibit a higher overall behavior disturbance compared to individuals with similar intellectual disability. Due to its multisystem disorder, family members, caregivers, physicians, dieticians, and speech-language pathologists all play an important role in the management and treatment of symptoms in an individual with PWS. This article reviews current research on behavior and cognition in PWS and discusses management guidelines for this disorder.

Pleiotropic role of IGF-I in obesity hypoventilation syndrome

CONTEXT

Obesity hypoventilation syndrome (OHS) is defined by the association between obesity and daytime arterial hypercapnia. The syndrome includes in variable proportion impaired diaphragmatic weakness, decreased central ventilatory drive and nearly systematically occurrence of sleep apnea. An increased cardio-vascular risk has been demonstrated compared to normocapnic obesity. IGF-I has a pleiotropic role in metabolism, ventilatory control, muscle function and cardiovascular protection.

OBJECTIVES AND DESIGN

We performed a case control study comparing somatotropic axis changes including IGF-I in obese with or without OHS.

METHODS

Patients underwent respiratory function tests, CO(2) ventilatory responses, polysomnography and somatotropic axis exploration (GH, IGF-I and IGFBP-3).

RESULTS

15 OHS (BMI: 41+/-5.6 kg/m(2), PaCO(2): 6.13+/-0.39 kPa, age: 55.6+/-5.9 years) and 15 matched obese without hypercapnia (BMI: 42+/-6.7 kg/m(2), PaCO(2): 5.13+/-0.27 kPa, age: 55.0+/-7.5 years) were compared. IGF-I and IGFBP-3 were significantly lowered in OHS, and negatively correlated with PaCO(2) (r=-0.615; P<0.001 and r=-0.452; P=0.016, respectively). Inspiratory capacity and forced vital capacity reflecting respiratory muscle strength decreased significantly with IGF-I (r=0.408; P=0.038). Triglycerides levels were higher in OHS (1.64+/-0.58 versus 1.13+/-0.56 g/L; P<0.01), and negatively associated with IGF-I (r=-0.418; P=0.027).

CONCLUSION

A low IGF-I level is associated with hypercapnia presumably by reducing ventilatory drive and favouring muscle weakness. The relationship between increased triglycerides and low IGF-I may represent one of mechanisms involved in the OHS increased cardio-vascular risk.

Short-term effects of growth hormone treatment on the upper airways of non severely obese children with Prader-Willi syndrome

AIMS

The aim of this study was to establish whether short-term GH treatment causes obstructive apnea in patients with Prader-Willi syndrome and normal upper airway patency.

SUBJECTS AND METHODS

We performed an observational longitudinal 6-week GH treatment study. Thirty-four non-severely obese Prader-Willi syndrome patients (20 boys, age range 0.94-11.8 yr, median 2.24 yr) entered an observational longitudinal 6-week study. Sixteen boys received recombinant human GH (rhGH) treatment; the remaining 18 represented the control group and received no treatment. Polysomnography monitoring and othorhinolaringoiatric video endoscopy were performed one night before and after 6 weeks of rhGH treatment (0.03 mg/kg body weight/day). All patients underwent auxologic assessment, fasting blood glucose, insulin and IGF-I evaluation. The main polysomnographic parameter considered was total apnea hypopnea index, consisting of two components: central apnea hypopnea index and obstructive apnea hypopnea index. All patients were free of severe or moderate upper airway obstruction when rhGH treatment began.

RESULTS

After 6 weeks of rhGH therapy, obstructive apnea hypopnea index increased in 8/16 (50%), decreased in 5/16 (31%), and did not change in 3/16 (19%) patients. The changes were not statistically significant. The rhGH-treated group did not differ from the control group for the apnea hypopnea index both before and after 6 weeks of treatment. Adenoids and tonsils showed a slight increase in 1 and 2 patients on rhGH treatment, respectively, and did not change in the untreated patients.

CONCLUSIONS

Our data show that short-term rhGH treatment does not cause restrictions of the upper airways in patients with Prader-Willi syndrome and normal upper airway patency.

The relationship between central adrenal insufficiency and sleep-related breathing disorders in children with Prader-Willi syndrome

BACKGROUND

The annual death rate of patients with Prader-Willi syndrome (PWS) is high (3%). Many deaths of children are sudden and unexplained. Sleep apneas have been suggested to play a role in sudden deaths. Recently, we discovered that 60% of patients with PWS suffer from central adrenal insufficiency (CAI) during stress.

OBJECTIVE

The aim was to study the relationship between CAI and sleep-related breathing disorders.

DESIGN

In 20 children with PWS who underwent a metyrapone test (30 mg/kg at 2330 h), sleep-related breathing was evaluated by polysomnography before the metyrapone test. In addition, we recorded sleep-related breathing in 10 children with PWS during their metyrapone test. CAI was diagnosed when ACTH levels during the metyrapone test were below 33 pmol/liter at 0730 h. All tests were performed during healthy condition.

SETTING

The study was conducted in a pediatric intensive care unit and specialized sleep center.

RESULTS

Median (interquartile range) age was 8.4 yr (6.5-10.2). After metyrapone administration, median (interquartile range) central apnea index (number/hour) increased significantly from 2.2 (0.4-4.7) to 5.2 (1.5-7.9) (P = 0.007). The increase tended to be higher in children with CAI [2.8 (2.0-3.9) vs. 1.0 (-0.2 to 2.6); P = 0.09]. During polysomnography before the metyrapone test, sleep-related breathing was worse in children with CAI, who had a significantly higher central apnea index and tended to have a lower minimum oxygen saturation compared to those without CAI (P = 0.03 and P = 0.07).

CONCLUSIONS

In children with PWS, the central apnea index increased significantly after metyrapone administration, particularly in those with CAI during stress. In addition, children with CAI had a higher central apnea index compared to those without several months before the metyrapone test.

High prevalence of central adrenal insufficiency in patients with Prader-Willi syndrome

CONTEXT

The annual death rate of Prader-Willi syndrome (PWS) patients is very high (3%). Many of these deaths are sudden and unexplained.

OBJECTIVE

Because most deaths occur during moderate infections and PWS patients suffer from various hypothalamic insufficiencies, we investigated whether PWS patients suffer from central adrenal insufficiency (CAI) during stressful conditions.

DESIGN

Overnight single-dose metyrapone tests were performed. Metyrapone (30 mg/kg) was administered at 2330 h. At 0400, 0600, and 0730 h, ACTH, 11-deoxycortisol, cortisol, and glucose levels were measured. Diurnal salivary cortisol profiles were assessed on a different day at wake-up, 30 min after wake-up, at 1400 h, and at 2000 h.

SETTING

The study was conducted in a pediatric intensive care unit.

PATIENTS

Patients included 25 randomly selected PWS patients.

MAIN OUTCOME MEASURE

Patients were considered as having CAI when ACTH levels remained below 33 pmol/liter at 0730 h.

RESULTS

Median (interquartile range) age was 9.7 (6.8-13.6) yr. Fifteen patients (60%) had an insufficient ACTH response (CAI, P < 0.001). There was no significant difference in age, gender, genotype, and body mass index SD score between patients with CAI and those without. Morning salivary cortisol levels and diurnal profiles were normal in all children, suggesting that CAI becomes apparent only during stressful conditions.

CONCLUSIONS

Strikingly, 60% of our PWS patients had CAI. The high percentage of CAI in PWS patients might explain the high rate of sudden death in these patients, particularly during infection-related stress. Based on our data, one should consider treatment with hydrocortisone during acute illness in PWS patients unless CAI has recently been ruled out with a metyrapone test.

Breathing disorders in Prader-Willi syndrome: the role of obesity, growth hormone treatment and upper respiratory tract infections

Prader-Willi syndrome is a neurogenetic disorder characterized by a number of signs and symptoms, including muscular hypotonia in infancy, hypogonadism, obesity and short stature. Neurobehavioral abnormalities and cognitive impairment are common. In addition, breathing abnormalities have been described, including sleep-related breathing disorders, abnormal chemoreceptor sensitivity and pulmonary function abnormalities. Growth hormone treatment is now widely used in children with Prader-Willi syndrome to improve growth and body composition. Over the last 4 years, case reports have been published concerning unexpected death, many of which were related to respiratory abnormalities. This review focuses on breathing abnormalities in Prader-Willi syndrome individuals and the influence of obesity, growth hormone treatment and upper respiratory tract infections.

Twenty years of recombinant human growth hormone in children: relevance to pediatric care providers

Recombinant human growth hormone has revolutionized the management of children and adolescents with growth hormone deficiency and other growth disorders, but clinical and ethical controversies remain regarding diagnostic approach, optimal recombinant human growth hormone dose and duration, and expected outcomes. Management of pubertal and transitioning patients with growth hormone deficiency has also commanded increased attention. Recent clinical studies that demonstrate the positive health benefits of recombinant human growth hormone in children with cystic fibrosis, inflammatory bowel disease, and juvenile rheumatoid arthritis have not yet clarified issues about patient selection and appropriate long-term use. An understanding of current recombinant human growth hormone indications and controversies can facilitate patient evaluation and expedite referral for potential treatment. This review summarizes current indications for recombinant human growth hormone use, discusses clinical challenges, and provides recommendations for pediatricians caring for children who may be appropriate candidates for recombinant human growth hormone therapy.

Effects of Growth Hormone Therapy on Glucose Metabolism and Insulin Sensitivity Indices in Prepubertal Children with Prader-Willi Syndrome

In Prader-Willi syndrome (PWS) growth hormone therapy (GHT) improves height, body composition, agility and muscular strength. In such patients it is necessary to consider the potential diabetogenic effect of GHT, since they tend to develop type 2 diabetes, particularly after the pubertal age. The aim of our study was to investigate the effects of GHT on glucose and insulin homeostasis in PWS children. An oral glucose tolerance test (OGTT) was performed in 24 prepubertal PWS children (15 male, 9 female, age: 5.8 +/- 2.8 years), 16 were obese (group A) and 8 had normal weight (group B), before and after 2.7 +/- 1.3 years GHT (0.22 +/- 0.03 mg/kg/week) and, only at baseline, in 35 prepubertal children with simple obesity (19 male, 16 female) (group C). Fasting glucose and insulin, glucose tolerance, insulin sensitivity index (ISI), homeostasis model assessment of insulin resistance (HOMA-IR), quick insulin check index (QUICKI), area under the curves (AUC) of glucose and insulin were estimated. At the start of GHT, all PWS children were normoglycaemic and normotolerant but two developed impaired glucose tolerance after 2.2 and 1.9 years of therapy, respectively. At baseline, group A showed lower fasting insulin levels, HOMA-IR and AUC of insulin, higher ISI, QUICKI and AUC of glucose than group C. Comparing groups A and B, AUC of insulin was higher and ISI lower in group A. During GHT, a significant increase of fasting insulin and glucose, a worsening of insulin resistance (HOMA-IR) and insulin sensitivity (QUICKI) was found only in group A while ISI did not change. The AUC of glucose decreased in both groups instead AUC of insulin did not change. BMI-SDS decreased in group A and increased in group B. The increased insulin resistance and decreased insulin sensitivity in obese PWS patients, as well as the occurrence of impaired glucose tolerance during GHT, suggest that a close monitoring of glucose and insulin homeostasis is mandatory, especially in treated obese PWS children.

Sleep-related breathing disorders in prepubertal children with Prader-Willi syndrome and effects of growth hormone treatment

CONTEXT

Recently, several cases of sudden death in GH-treated and non-GH-treated, mainly young Prader-Willi syndrome (PWS), patients were reported. GH treatment in PWS results in a remarkable growth response and an improvement of body composition and muscle strength. Data concerning effects on respiratory parameters, are however, limited.

OBJECTIVE

The objective of the study was to evaluate effects of GH on respiratory parameters in prepubertal PWS children.

DESIGN

Polysomnography was performed before GH in 53 children and repeated after 6 months of GH treatment in 35 of them.

PATIENTS

Fifty-three prepubertal PWS children (30 boys), with median (interquartile range) age of 5.4 (2.1-7.2) yr and body mass index of +1.0 sd score (-0.1-1.7).

INTERVENTION

Intervention included treatment with GH 1 mg/m2.d.

RESULTS

Apnea hypopnea index (AHI) was 5.1 per hour (2.8-8.7) (normal 0-1 per hour). Of these, 2.8 per hour (1.5-5.4) were central apneas and the rest mainly hypopneas. Duration of apneas was 15.0 sec (13.0-28.0). AHI did not correlate with age and body mass index, but central apneas decreased with age (r = -0.34, P = 0.01). During 6 months of GH treatment, AHI did not significantly change from 4.8 (2.6-7.9) at baseline to 4.0 (2.7-6.2; P = 0.36). One patient died unexpectedly during a mild upper respiratory tract infection, although he had a nearly normal polysomnography.

CONCLUSIONS

PWS children have a high AHI, mainly due to central apneas. Six months of GH treatment does not aggravate the sleep-related breathing disorders in young PWS children. Our study also shows that monitoring during upper respiratory tract infection in PWS children should be considered.

Anesthesia and Prader-Willi syndrome: preliminary experience with regional anesthesia

The constellation of neonatal hypotonia, developmental delay, hypogonadism and obesity caused by hyperphagia was first reported in 1956 and subsequently termed Prader-Willi syndrome (PWS). Genetic analysis has demonstrated abnormalities of chromosome 15. Anesthesia concerns of PWS include morbid obesity, the potential for difficulties with airway management, risk for perioperative respiratory failure, abnormalities in the central control of ventilation and temperature, rare reports of primary myocardial involvement, aggressive and at times violent behavior and glucose intolerance. For the first time, we report the use of regional anesthesia in four patients with PWS. A lumbar plexus catheter was used to provide postoperative analgesia in one patient while regional anesthesia (fasica iliaca block, spinal anesthesia, and lateral vertical infraclavicular block) was used to provide primary intraoperative anesthesia in three other patients while avoiding the need for general anesthesia. Previous reports of the anesthesia care of patients with PWS are reviewed and the potential perioperative implications of the sequelae of PWS are discussed.

Development of chemoreceptor responses in infants

This paper is devoted to the field of chemoreception and its role in the control of breathing in infants. We use "chemoreception" to refer to the capacity to sense and process changes in P(O2) and P(CO2), and also to react to these changes by adjusting ventilation in order to maintain homeostasis. Functional chemoreceptors are not essential to commence or even to sustain breathing efforts immediately at or after birth; the intense brain activation, which occurs at birth, is sufficient. Over subsequent days to weeks, however, this "neurogenic" drive weakens and drive from the chemoreceptors becomes critical for generating and maintaining a normal breathing rhythm. Failure of the chemoreceptors to develop normally, consequently, becomes an important underlying cause of breathing dysfunction, particularly during sleep. The paper deals with the methods available to study chemoreception in newborn infants and provide an overview of the early postnatal changes and interactions, which influence breathing at rest and under stress. The latter may be described in terms of the threshold and strength as well as the delay/speed with which ventilation changes in response to chemical stimulation. We conclude with a survey of disorders associated with chemoreceptor deficits in infancy.

Death in two female Prader-Willi syndrome patients during the early phase of growth hormone treatment

Reports on sudden death in Prader-Willi syndrome (PWS) patients after the start of growth hormone (GH) treatment have been published recently. We observed a 4.7-y-old girl who showed a continuous increase in pulmonary artery pressure and died of cardiorespiratory failure 7 wk after GH therapy had been initiated, and a 9.3-y-old girl with additional trisomy 21 who died during a minor respiratory infection 6 mo after GH had been started. Both patients were overweight (weight for height 127% and 224%, respectively). GH-induced fluid retention may have occurred in the younger girl. In contrast to the reported cases, our PWS patients were female.

CONCLUSION

Our cases illustrate the difficulty of differentiation between possible GH side effects and the natural course of disease, in particular with respect to obesity-related comorbidity and mortality.

Death during GH therapy in children with Prader-Willi syndrome: description of two new cases

A few cases of death worldwide during GH treatment in pediatric patients with Prader-Willi syndrome (PWS) have been recently described. The evaluation of further cases is needed to better identify possible causal mechanism(s), as well as to suggest some additional guidelines for prevention. We report the death of 2 additional children with genetically confirmed PWS in the first months of GH therapy. Case 1: This 3.9-yr-old girl was born at 39 weeks gestation. Low GH response to two stimulation tests was observed. GH administration was started at the age of 3.5 yr (0.33 mg/kg per week), when the patient was at 130% of her ideal body weight (ibw). Hypertrophy of adenoids was previously demonstrated. Snoring and sleep apnea were present before GH treatment, and did not increase during therapy. Four months later she died at home suddenly in the morning. Case 2: This patient was a 6.3-yr-old boy. He was born at term after an uneventful pregnancy. At the age of 6 yr, his weight was at 144% of his ibw. He showed reduced GH secretion during provocation tests, and GH therapy was started (0.20 mg/kg per week). The previously reported nocturnal respiratory impairment had worsened after beginning GH administration. Tonsils and adenoids hypertrophy were noted. At the age of 6.3 yr he died at home in the morning following an acute crisis of apnea. These additional cases seem to confirm that some children with PWS may be at risk of sudden death at the beginning of GH therapy.

Deaths in children with Prader-Willi syndrome. A contribution to the debate about the safety of growth hormone treatment in children with PWS

Irrespective of GH treatment, children with Prader-Willi syndrome (PWS) suffer more frequently and more seriously from respiratory problems than healthy children. The pathogenesis of such respiratory problems in PWS seems to be multifactorial in origin, but mainly related to insufficiency of respiratory muscles and pharyngeal narrowness. Deaths of children with PWS are reported among GH treated as well as untreated children. Our data show that also disturbed body composition plays an important role in fatal outcomes, possibly enhancing the ventilation disorder. For several years, in our recommendations we have pointed out the secondary risks of increasing obesity. In addition, it is recommended for all children with PWS, in particular before institution of GH therapy, to have polysomnography and an otorhinolaryngologic examination performed, and tonsillectomy in the case of enlarged tonsils. Furthermore, upper airway infections should be treated aggressively.