Polysomnographic characteristics in patients with mucopolysaccharidoses

Pediatric Sleep Respiratory Disorders: A Narrative Review of Epidemiology and Risk Factors

Sleep is a fundamental biological necessity, the lack of which has severe repercussions on the mental and physical well-being in individuals of all ages. The phrase "sleep-disordered breathing (SDB)" indicates a wide array of conditions characterized by snoring and/or respiratory distress due to increased upper airway resistance and pharyngeal collapsibility; these range from primary snoring to obstructive sleep apnea (OSA) and occur in all age groups. In the general pediatric population, the prevalence of OSA varies between 2% and 5%, but in some particular clinical conditions, it can be much higher. While adenotonsillar hypertrophy ("classic phenotype") is the main cause of OSA in preschool age (3-5 years), obesity ("adult phenotype") is the most common cause in adolescence. There is also a "congenital-structural" phenotype that is characterized by a high prevalence of OSA, appearing from the earliest ages of life, supported by morpho-structural abnormalities or craniofacial changes and associated with genetic syndromes such as Pierre Robin syndrome, Prader-Willi, achondroplasia, and Down syndrome. Neuromuscular disorders and lysosomal storage disorders are also frequently accompanied by a high prevalence of OSA in all life ages. Early recognition and proper treatment are crucial to avoid major neuro-cognitive, cardiovascular, and metabolic morbidities.

Evaluation of sleep-disordered breathing and its relationship with respiratory parameters in children with mucopolysaccharidosis Type IVA and VI

The aims of the study were to evaluate the prevalence of sleep-disordered breathing (SDB) by using polysomnography (PSG) in children with MPS IVA and MPS VI who underwent enzyme replacement therapy (ERT) and to analyze the effect on SDB of having upper airway surgery, pulmonary functions, and exercise capacity. A retrospective cross-sectional study was conducted on patients with MPS IVA (n:17) and MPS VI (n:11) aged under 19 years who underwent polysomnography. Descriptive and nonparametric analyses were performed for demographic, PSG, pulmonary function and exercise capacity variables. The frequency of sleep apnea in the study sample was 85.7% (24/28). Four patients (14.3%) had no sleep apnea, 15 (53.6%) had mild, and nine (32.1%) had moderate-to-severe sleep apnea. Two patients (7.1%) had central sleep apnea and 22 had obstructive sleep apnea (OSA) (78.6%). Forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were negatively correlated to apnea-hypopnea index (AHI) (r = -0.594, p = .009; r = -0.636, p = .005, respectively). Despite ERT and previous upper airway surgery, the prevalence of OSA was high in patients with MPS IVA-MPS IV, emphasizing the importance of PSG screening for sleep disorders. Pulmonary function tests may be useful for predicting sleep apnea in patients with MPS IVA and MPS VI.

Otorhinolaryngological Management in Taiwanese Patients with Mucopolysaccharidoses

Background: Mucopolysaccharidoses (MPSs) are lysosomal storage disorders wherein glycosaminoglycans accumulate because the enzymes that degrade them are insufficient. The earliest symptoms, which are the main reasons for seeking consultation, are otorhinolaryngological and commonly occur in MPS I, II, IV, and VI. This retrospective study aimed to determine the occurrence of otorhinolaryngological manifestations in MPS patients in Taiwan and to analyze the prognosis of surgical intervention, including its effect on symptoms. Methods: We reviewed 42 patients (30 males and 12 females), with a median age of 20.5 years, who had MPS (16.7% type I, 35.7% type II, 19.0% type IIIB, 21.4% type IVA, and 7.2% type VI). The following otorhinolaryngological manifestations were collected: annual number of upper respiratory tract infections (URTIs) and otitis media with effusion (OME) episodes, adenoid size, tonsillar size, and apnea-hypopnea index (AHI). Results: Among 42 patients, we found recurrent otitis media in 42.9% of the patients, hearing loss in 83.3% (mixed: 52.4%, conductive: 21.4%, and sensorineural: 9.5%), frequent URTIs in 47.6%, and obstructive sleep apnea syndrome in 35.7%. Moreover, 76% of the patients underwent ear, nose, and throat (ENT) surgery, including adenoidectomy, tonsillectomy, tympanostomy with ventilation tube insertion, tracheotomy, and supraglottoplasty. Conclusions: MPS patients had a high incidence of ENT problems. ENT surgery reduced the severity of hearing loss, degree of symptoms related to upper airway obstruction, and severity of respiratory tract and otological infections of patients with MPS.

Intravenous Enzyme Replacement Therapy in Mucopolysaccharidoses: Clinical Effectiveness and Limitations

The aim of this review is to summarize the evidence on efficacy, effectiveness and safety of intravenous enzyme replacement therapy (ERT) available for mucopolysaccharidoses (MPSs) I, II, IVA, VI and VII, gained in phase III clinical trials and in observational post-approval studies. Post-marketing data are sometimes conflicting or controversial, possibly depending on disease severity, differently involved organs, age at starting treatment, and development of anti-drug antibodies (ADAs). There is general agreement that ERT is effective in reducing urinary glycosaminoglycans and liver and spleen volume, while heart and joints outcomes are variable in different studies. Effectiveness on cardiac valves, trachea and bronchi, hearing and eyes is definitely poor, probably due to limited penetration in the specific tissues. ERT does not cross the blood-brain barrier, with the consequence that the central nervous system is not cured by intravenously injected ERT. All patients develop ADAs but their role in ERT tolerance and effectiveness has not been well defined yet. Lack of reliable biomarkers contributes to the uncertainties about effectiveness. The data obtained from affected siblings strongly indicates the need of neonatal screening for treatable MPSs. Currently, other treatments are under evaluation and will surely help improve the prognosis of MPS patients.

Non-invasive Ventilation and CPAP Failure in Children and Indications for Invasive Ventilation

Non-invasive ventilation (NIV) and continuous positive airway pressure (CPAP) are effective treatments for children with severe sleep disordered breathing (SBD). However, some patients may present too severe SDB that do not respond to NIV/CPAP or insufficient compliance to treatment. A careful revaluation of the interface and of ventilator settings should be performed before considering alternative treatments. In patients with obstructive sleep apnea (OSA), alternatives to CPAP/NIV rely on the underlying disease. Ear-nose-throat (ENT) surgery such as adeno-tonsillectomy (AT), turbinectomy or supraglottoplasty represent an effective treatment in selected patients before starting CPAP/NIV and should be reconsidered in case of CPAP failure. Rapid maxillary expansion (RME) is restricted to children with OSA and a narrow palate who have little adenotonsillar tissue, or for those with residual OSA after AT. Weight loss is the first line therapy for obese children with OSA before starting CPAP and should remain a priority in the long-term. Selected patients may benefit from maxillo-facial surgery such as mandibular distraction osteogenesis (MDO) or from neurosurgery procedures like fronto-facial monobloc advancement. Nasopharyngeal airway (NPA) or high flow nasal cannula (HFNC) may constitute efficient alternatives to CPAP in selected patients. Hypoglossal nerve stimulation has been proposed in children with Down syndrome not tolerant to CPAP. Ultimately, tracheostomy represents the unique alternative in case of failure of all the above-mentioned treatments. All these treatments require a multidisciplinary approach with a personalized treatment tailored on the different diseases and sites of obstruction. In patients with neuromuscular, neurological or lung disorders, non-invasive management in case of NIV failure is more challenging. Diaphragmatic pacing has been proposed for some patients with central congenital hypoventilation syndrome (CCHS) or neurological disorders, however its experience in children is limited. Finally, invasive ventilation via tracheotomy represents again the ultimate alternative for children with severe disease and little or no ventilatory autonomy. However, ethical considerations weighting the efficacy against the burden of this treatment should be discussed before choosing this last option.

An At-Risk Population Screening Program for Mucopolysaccharidoses by Measuring Urinary Glycosaminoglycans in Taiwan

Background: The mucopolysaccharidoses (MPSs) are a group of rare lysosomal storage disorders characterized by the accumulation of glycosaminoglycans (GAGs) and which eventually cause progressive damage to various tissues and organs. We developed a feasible MPS screening algorithm and established a cross-specialty collaboration platform between medical geneticists and other medical specialists based on at-risk criteria to allow for an earlier confirmative diagnosis of MPS. Methods: Children (<19 years of age) with clinical signs and symptoms compatible with MPS were prospectively enrolled from pediatric clinics between July 2013 and June 2018. Urine samples were collected for a non-specific total GAG analysis using the dimethylmethylene blue (DMB) spectrophotometric method, and the quantitation of three urinary GAGs (dermatan sulfate (DS), heparan sulfate (HS), and keratan sulfate (KS)) was performed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). The subjects with elevated urinary GAG levels were recalled for leukocyte enzyme activity assay and genetic testing for confirmation. Results: Among 153 subjects enrolled in this study, 13 had a confirmative diagnosis of MPS (age range, 0.6 to 10.9 years—three with MPS I, four with MPS II, five with MPS IIIB, and one with MPS IVA). The major signs and symptoms with regards to different systems recorded by pediatricians at the time of the decision to test for MPS were the musculoskeletal system (55%), followed by the neurological system (45%) and coarse facial features (39%). For these 13 patients, the median age at the diagnosis of MPS was 2.9 years. The false negative rate of urinary DMB ratio using the dye-based method for these 13 patients was 31%, including one MPS I, two MPS IIIB, and one MPS IVA. However, there were no false negative results with urinary DS, HS and KS using the MS/MS-based method. Conclusions: We established an at-risk population screening program for MPS by measuring urinary GAG fractionation biomarkers using the LC-MS/MS method. The program included medical geneticists and other medical specialists to increase awareness and enable an early diagnosis by detecting MPS at the initial onset of clinical symptoms.

Obstructive sleep apnea and craniofacial appearance in MPS type I-Hurler children after hematopoietic stem cell transplantation

OBJECTIVES

Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal storage disorder characterized by severe multi-systemic organ manifestations including obstructive sleep apnea syndrome (OSAS). Hematopoietic stem cell transplantation (HSCT) is the treatment of choice in severe MPS I (MPS IH, Hurler syndrome). However, the effect of HSCT on OSAS in MPS IH still remains unclear. The purpose of this study was to analyze respiratory patterns during sleep following HSCT in MPS IH children and to relate these findings to craniofacial abnormalities.

METHODS

Overnight polysomnographies of nine MPS IH children (mean age: 8.2 years) previously treated with HSCT were retrospectively analyzed. Magnetic resonance images of the head were assessed with regard to soft and hard tissue abnormalities of the upper respiratory tract.

RESULTS

The mean apnea hypopnea index (AHI) was 5.3 events/h (range, 0.3-12.2), and the majority of apnea/hypopneas were obstructive. Whereas two patients had severe OSAS (AHI > 10) and two moderate OSAS (5 > AHI < 10), five patients had no evidence of OSAS (AHI < 2.0). Donor cell chimerism was significantly lower in MPS IH patients with OSAS as compared to patients without OSAS (p < 0.001). The upper airway space and the maxilla were significantly smaller and the adenoids larger in MPS IH patients with OSAS as compared to those of non-OSAS patients.

CONCLUSION

OSAS was only observed in MPS IH patients with graft failure or low donor cell chimerism. Conversely, successful HSCT seems to ameliorate adenoid hyperplasia and maxillary constriction in MPS IH patients and thereby minimizes the risk of OSAS at least at younger ages.

Recommendations for the management of MPS VI: systematic evidence- and consensus-based guidance

Introduction

Mucopolysaccharidosis (MPS) VI or Maroteaux-Lamy syndrome (253200) is an autosomal recessive lysosomal storage disorder caused by deficiency in N-acetylgalactosamine-4-sulfatase (arylsulfatase B). The heterogeneity and progressive nature of MPS VI necessitates a multidisciplinary team approach and there is a need for robust guidance to achieve optimal management. This programme was convened to develop evidence-based, expert-agreed recommendations for the general principles of management, routine monitoring requirements and the use of medical and surgical interventions in patients with MPS VI.

Methods

26 international healthcare professionals from various disciplines, all with expertise in managing MPS VI, and three patient advocates formed the Steering Committee group (SC) and contributed to the development of this guidance. Members from six Patient Advocacy Groups (PAGs) acted as advisors and attended interviews to ensure representation of the patient perspective. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with expertise and experience managing patients with MPS VI and the manuscript has been evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers.

Results

A total of 93 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions. Consensus was reached on all statements after two rounds of voting. The greatest challenges faced by patients as relayed by consultation with PAGs were deficits in endurance, dexterity, hearing, vision and respiratory function. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance).

Conclusion

This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS VI and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1080-y) contains supplementary material, which is available to authorized users.

ENT and mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a heterogeneous group of inherited metabolic disorders, each associated with a deficiency in one of the enzymes involved in glycosaminoglycan (GAG) catabolism. Over time, GAGs accumulate in cells and tissues causing progressive damage, a variety of multi-organ clinical manifestations, and premature death. Ear, nose, and throat (ENT) disorders affect more than 90% of MPS patients and appear in the early stage of MPS; also reported are recurrent otitis media and persistent otitis media with effusion, macroglossia, adenotonsillar hypertrophy, nasal obstruction, obstructive sleep apnoea syndrome (OSAS), hearing loss, and progressive respiratory disorders. Undiagnosed MPS patients are frequently referred to otolaryngologists before the diagnosis of MPS is confirmed. Otolaryngologists thus have an early opportunity to recognize MPS and they can play an increasingly integral role in the multidisciplinary approach to the diagnosis and management of many children with MPS. The ENT commitment is therefore to suspect MPS when non-specific ENT pathologies are associated with repeated surgical treatments, unexplainable worsening of diseases despite correct treatment, and with signs, symptoms, and pathological conditions such as hepatomegaly, inguinal hernia, macrocephaly, macroglossia, coarse facial features, hydrocephalous, joint stiffness, bone deformities, valvular cardiomyopathy, carpal tunnel syndrome, and posture and visual disorders.

The relationships between urinary glycosaminoglycan levels and phenotypes of mucopolysaccharidoses

Background

The aim of this study was to use the liquid chromatography/tandem mass spectrometry (LC‐MS/MS) method to quantitate levels of three urinary glycosaminoglycans (GAGs; dermatan sulfate [DS], heparan sulfate [HS], and keratan sulfate [KS]) to help make a correct diagnosis of mucopolysaccharidosis (MPS).

Methods

We analyzed the relationships between phenotypes and levels of urinary GAGs of 79 patients with different types of MPS.

Results

The patients with mental retardation (n = 21) had significantly higher levels of HS than those without mental retardation (n = 58; 328.8 vs. 3.2 μg/ml, p < 0.001). The DS levels in the patients with hernia, hepatosplenomegaly, claw hands, coarse face, valvular heart disease, and joint stiffness were higher than those without. Twenty patients received enzyme replacement therapy (ERT) for 1–12.3 years. After ERT, the KS level decreased by 90% in the patients with MPS IVA compared to a 31% decrease in the change of dimethylmethylene blue (DMB) ratio. The DS level decreased by 79% after ERT in the patients with MPS VI compared to a 66% decrease in the change of DMB ratio.

Conclusions

The measurement of GAG fractionation biomarkers using the LC‐MS/MS method is a more sensitive and reliable tool than the DMB ratio for MPS high‐risk screening, diagnosis, subclass identification, and monitoring the efficacy of ERT.

Sleep-disordered breathing in paediatric setting: existing and upcoming of the genetic disorders

Childhood obstructive sleep apnea syndrome (OSAS) is characterized by anatomical and functional upper airway abnormalities as pathophysiological determinants, and clinical symptoms are frequently clear. OSAS is widely described in rare genetic disorders, such as achondroplasia, Down syndrome, Prader-Willi syndrome, Pierre Robin sequence, and mucopolysaccharidosis. Craniofacial and upper airway involvement is frequently morbid conditions. In children with genetic diseases, the clinical symptoms of OSAS are often slight or absent, and related morbidities are usually more severe and can be observed at any age. The present review is aimed to updating the discoveries regarding OSAS on Achondroplasia, Down syndrome, Prader-Willi syndrome, Pierre Robin sequence, Sickle cell disease, or encountered in our clinical practice (Ehlers-Danlos syndrome, Ellis-van Creveld syndrome, Noonan syndrome). Two additional groups of genetic disorders will be focused (mucopolysaccharidoses and osteogenesis imperfecta). The flowing items are covered for each disease: (I) what is the pathophysiology of OSAS? (II) What is the incidence/prevalence of OSAS? (III) What result from the management and prognosis? (IV) What are the recommendations? Considering the worries of OSAS, such as inattention and behavioural problems, daytime sleepiness, failure to thrive, cardiological and metabolic complications, the benefit of a widespread screening and the treatment in children with genetic diseases is undoubtful. The goals of the further efforts can be the inclusion of various genetic diseases into guidelines for the screening of OSAS, updating the shreds of evidence based on the research progression.

Mucopolysaccharidosis III in Taiwan: Natural history, clinical and molecular characteristics of 28 patients diagnosed during a 21-year period

Mucopolysaccharidosis type III (MPS III, Sanfilippo syndrome) has a variable age of onset and variable rate of progression. However, information regarding the natural history of this disorder in Asian populations is limited. A retrospective analysis was carried out for 28 patients with MPS III (types IIIA [n = 3], IIIB [n = 23], and IIIC [n = 2]; 15 males and 13 females; median age, 8.2 years; age range, 2.7-26.5 years) seen in six medical centers in Taiwan from January 1996 through October 2017. The median age at confirmed diagnosis was 4.6 years. The most common initial symptom was speech delay (75%), followed by hirsutism (64%) and hyperactivity (54%). Both z scores for height and weight were negatively correlated with age (r = -.693 and -0.718, respectively; p < .01). The most prevalent clinical manifestations were speech delay (100%) and intellectual disability (100%), followed by hirsutism (93%), hyperactivity (79%), coarse facial features (68%), sleep disorders (61%), and hepatosplenomegaly (61%). Ten patients (36%) had epilepsy, and the median age at the first seizure was 11 years. Thirteen patients (46%) experienced at least one surgical procedure. At the time of the present study, 7 of the 28 patients had passed away at the median age of 13.0 years. Molecular studies showed an allelic heterogeneity without clear genotype and phenotype correlations. MPS IIIB is the most frequent subtype among MPS III in the Taiwanese population. An understanding of the natural history of MPS III may allow early diagnosis and timely management of the disease facilitating better treatment outcomes.

Pathophysiology, evaluation, and management of sleep disorders in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) represent a heterogeneous group of lysosomal storage disorders, each one associated with a deficiency in one of the enzymes involved in glycosaminoglycan degradation. Sleep disorders are a frequent manifestation of all types of MPS. Underlying causes are diverse and comprised of both respiratory and central nervous system (CNS) abnormalities. Sleep disordered breathing such as obstructive sleep apnea and nocturnal hypoventilation can arise in patients with upper airway obstruction and/or with alterations in respiratory mechanics, causing restrictive pulmonary disease. MPS patients with CNS disease can also develop sleep disturbances unrelated to ventilatory impairments, often associated with severe behavioral problems or night-time epileptic seizures. The present review discusses the pathophysiology, evaluation, and management of sleep disorders in MPS based on information from a meeting on the brain in MPS, attended by an international group of experts (April 28-30, 2016, Stockholm, Sweden), and additional literature searches.

Sleep Disorders in Childhood Neurogenetic Disorders

enetic advances in the past three decades have transformed our understanding and treatment of many human diseases including neurogenetic disorders. Most neurogenetic disorders can be classified as "rare disease," but collectively neurogenetic disorders are not rare and are commonly encountered in general pediatric practice. The authors decided to select eight relatively well-known neurogenetic disorders including Down syndrome, Angelman syndrome, Prader-Willi syndrome, Smith-Magenis syndrome, congenital central hypoventilation syndrome, achondroplasia, mucopolysaccharidoses, and Duchenne muscular dystrophy. Each disorder is presented in the following format: overview, clinical characteristics, developmental aspects, associated sleep disorders, management and research/future directions.

Central sleep apnea in children: experience at a single center

OBJECTIVE

Central sleep apnea (CSA) syndromes are rare in children and data in children over one year of age are scarce. The aim of the study was to describe the sleep characteristics, underlying disorders, management, and outcome of children with CSA.

PATIENTS/METHODS

A retrospective chart review of all children >1 year of age, diagnosed with CSA on a laboratory sleep study during a 20-month period, was performed. CSA was defined by a central apnea index (CAI) >5 events/h. The clinical management and the patient's outcome were analyzed.

RESULTS

Eighteen of 441 (4.1%) patients recorded during the study period had CSA. The median CAI, pulse oximetry, and oxygen desaturation index were 13/h (range 6-146), 96% (93-98%), and 18/h (6-98), respectively. Neurosurgical pathologies represented the most common underlying disorders with Arnold-Chiari malformation in four and ganglioglioma in three patients. Other underlying disorders were Prader-Willi syndrome (N = 3), achondroplasia (N = 2), and Down syndrome, with one patient having an achondroplasia and a Down syndrome. The remaining six patients had other genetic diseases. The most common investigation was brain magnetic resonance imaging (MRI). Individualized management with neurosurgery and/or chemotherapy, continuous positive airway pressure (in two patients having associated obstructive events), or noninvasive ventilation resulted in an improvement in CSA and the clinical presentation in 11 patients.

CONCLUSION

CSA is rare in children >1 year of age. Underlying disorders are dominated by neurosurgical disorders. Individualized management is able to improve CSA and the clinical condition in most patients.

Mucopolysaccharidosis I; Parental beliefs about the impact of disease on the quality of life of their children

Background

Hematopoietic stem cell transplants, alongside enzyme replacement therapy and good multi-disciplinary care, have dramatically improved the life expectancy in children with Mucopolysaccharidosis (MPS) I, with better objective and functional outcomes. Despite these improvements, children with both the attenuated (non-Hurler) and severe (Hurler) variants of the disease have marked residual morbidity. Children with MPS I suffer with head and neck disease including obstructive sleep apnoea and hearing loss. The impact of these on quality of life has been poorly researched and no previous work has been published looking at patients’ perception of their own health, an important domain when considering the impact of treatment.

Methods

This exploratory qualitative study aimed to discover the effect of head and neck disease, alongside that of MPS I as a whole, on the quality of life of affected children.

A grounded theory approach was used to conduct this study. Children and their parents were invited to participate in semi-structured interviews. The transcribed interviews were coded and emergent themes explored until saturation occurred.

Results

The families of eleven children with MPS I were interviewed, five with Hurler’s and six with the attenuated non-Hurler’s. Important themes to emerge were- the fear of dying associated with obstructive sleep apnoea, difficulties communicating at school due to the delayed acquisition of language, chronic pain and restricted mobility, physical differences and restricted participation in social activities such as sports secondary to the musculoskeletal disease burden. The overall theme running through the analysis was the desire to fit in with ones peers.

Conclusion

Parents and children with MPS 1 worry about ‘fitting-in’ with broader society. The presence of airway disease has a profound impact on the emotional well being of parents whilst language delay and musculoskeletal disease have the biggest impact on the quality of life of the children themselves. It is important to understand the impact of MPS I on the quality of life of children and their families so that we may improve future treatment and management of this sub-group of children who have an increasing life span.

Tracheobronchial stents in mucopolysaccharidosis

INTRODUCTION

The mucopolysaccharidoses are a group of hereditary disorders pathologically characterized by tissue accumulation of glycosaminoglycans due to deficient lysosomal metabolism which often leads to progressive airway stenosis and respiratory insufficiency. Relentless and treatment-refractory narrowing of the lower airways with ensuing severe limitation of quality of life is a challenging problem in mucopolysaccharidoses.

CASE REPORTS

We report 2 cases of MPS (Hunter's and Maroteaux-Lamy's syndrome resp.) in whom tracheal stents were placed to relieve severe tracheal obstruction. The first patient could be weaned from mechanical ventilation after stent placement but showed significant long-term stent-related morbidity. The second patient suffered a severe procedure-related complication due to positioning problems typical for MPS.

CONCLUSIONS

Very good short-term success can be achieved with airway stent placement in patients with MPS and severe lower airway stenosis but a high risk of severe complications and important long-term morbidity have to be weighed against potential individual benefit.

Establishing a Role for Polysomnography in Hospitalized Children

BACKGROUND

Children with medical complexity have a high prevalence of sleep disorders. However, outpatient polysomnography to evaluate for these conditions may be difficult to perform because of lack of skilled nursing care. The aim of this study was to explore polysomnography indications in hospitalized children and assess its impact on patient care.

METHODS

Data from 85 inpatient polysomnographies of 70 children hospitalized between March and December 2014 were retrospectively collected.

RESULTS

Sixty percent of patients were boys with ages 6.5 ± 6 years. Chronic respiratory failure was present in 33.8%, airway obstruction due to defects of the tracheobronchial tree or craniofacial abnormalities in 54.3%, neurological complications of the perinatal period in 22.9%, genetic syndromes and neurodegenerative disorders in 31.4%, congenital myopathies in 5.7%, metabolic diseases in 4.3% and congenital cyanotic heart defects in 4.3%. Indications for polysomnography included assessment of chronic pulmonary disease (60%), ventilator requirements (41.2%), apnea/desaturation (23.5%), and acute life-threatening events (1.2%). Abnormal results were found in 89.4%. The observed diagnosis was obstructive sleep apnea in 64.7%, signs of chronic lung disease in 34.1%, hypoventilation in 9.4%, periodic breathing in 3.5%, and periodic limb movement of sleep in 4.7%. The following interventions were performed: adjustment of ventilator parameters (45.8%), positive airway pressure initiation (24.7%), otorhinolaryngology referral (30.6%), supraglottoplasty (2.4%), tracheostomy decannulation (2.4%), and tracheostomy placement (3.5%). Nine patients had available follow-up polysomnograms, all showing improvement in sleep variables after adherence to recommended interventions.

CONCLUSIONS

In individuals with complex medical disorders, inpatient polysomnographies give invaluable information to guide immediate medical decision making and should be strongly considered if resources allow this.

Obstructive sleep apnea syndrome after hematopoietic stem cell transplantation in children with mucopolysaccharidosis type I

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is very common in mucopolysaccharidosis I (MPS I). Hematopoietic stem cell transplantation (HSCT) is the preferred treatment for patients with severe MPS I diagnosed early in life. The protective effect of HSCT on the development of long term OSAS is not known.

METHODS

Overnight polysomnography (PSG) and biomarker data were analyzed during the annual follow-up in consecutive MPS I patients treated with HSCT.

RESULTS

The data of 13 patients (6 boys) were analyzed. Median age at HSCT was 17 (range 14-19) months, median age at PSG was 9.0 (4.5-14.5) years, and median time elapsed since HSCT was 7.6 (2.4-13.2) years. A significant correlation was observed between time elapsed since HSCT and the apnea-hypopnea index (AHI, r(2)=0.493, p=+0.003) and the oxygen desaturation index (r(2)=0.424, p=+0.02). Patients older than 10 years of age had a higher mean AHI (25.8/h vs 1.4/h, p=0.0008), a lower mean pulse oximetry (94.7% vs 97.2%, p=0.01) and a higher mean hypopnea index (18.8 vs 0.71/h, p=0.016) as compared to those younger than 10 years of age. No correlation was observed between the AHI and the metabolic clearance, assessed by urine glycosaminoglycan (GAG) excretion and residual enzyme activity, although there was a positive trend for the urinary GAG/higher normal value for age ratio (p=0.09).

CONCLUSION

HSCT does not offer long term protection against OSAS in MPS I with OSAS being documented in all patients after a time elapse since HSCT exceeding 10 years. The potential benefit of additional enzyme replacement therapy needs to be assessed.

Obstructive sleep disordered breathing in 2- to 18-year-old children: diagnosis and management

This document summarises the conclusions of a European Respiratory Society Task Force on the diagnosis and management of obstructive sleep disordered breathing (SDB) in childhood and refers to children aged 2-18 years. Prospective cohort studies describing the natural history of SDB or randomised, double-blind, placebo-controlled trials regarding its management are scarce. Selected evidence (362 articles) can be consolidated into seven management steps. SDB is suspected when symptoms or abnormalities related to upper airway obstruction are present (step 1). Central nervous or cardiovascular system morbidity, growth failure or enuresis and predictors of SDB persistence in the long-term are recognised (steps 2 and 3), and SDB severity is determined objectively preferably using polysomnography (step 4). Children with an apnoea-hypopnoea index (AHI) >5 episodes·h(-1), those with an AHI of 1-5 episodes·h(-1) and the presence of morbidity or factors predicting SDB persistence, and children with complex conditions (e.g. Down syndrome and Prader-Willi syndrome) all appear to benefit from treatment (step 5). Treatment interventions are usually implemented in a stepwise fashion addressing all abnormalities that predispose to SDB (step 6) with re-evaluation after each intervention to detect residual disease and to determine the need for additional treatment (step 7).

Actigraphic investigation of circadian rhythm functioning and activity levels in children with mucopolysaccharidosis type III (Sanfilippo syndrome)

BACKGROUND

Sleep disturbance is part of the behavioural phenotype of the rare genetic condition mucopolysaccharidosis (MPS) type III. A growing body of evidence suggests that underlying disturbance in circadian rhythm functioning may explain sleep problems within the MPS III population.

METHODS

Actigraphic data were recorded in eight children with MPS III over 7-10 days and compared to age-matched typically developing controls. Parameters of circadian rhythmicity and activity levels across a 24-h period were analysed.

RESULTS

Statistically and clinically significant differences between the two groups were noted. Analysis indicated that children with MPS III showed significantly increased fragmentation of circadian rhythm and reduced stability with external cues (zeitgebers), compared to controls. Average times of activity onset and offset were indicative of a phase delayed sleep-wake cycle for some children in the MPS III group. Children with MPS III had significantly higher activity levels during the early morning hours (midnight-6 am) compared to controls.

CONCLUSIONS

Results are consistent with previous research into MPS III and suggest that there is an impairment in circadian rhythm functioning in children with this condition. Implications for clinical practice and the management of sleep difficulties are discussed.

Sleep disordered breathing in mucopolysaccharidosis I: a multivariate analysis of patient, therapeutic and metabolic correlators modifying long term clinical outcome

Background

The lysosomal storage disorder, mucopolysaccharidosis I (MPS I), commonly manifests with upper airway obstruction and sleep disordered breathing (SDB). The success of current therapies, including haematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT) may be influenced by a number of factors and monitored using biomarkers of metabolic correction. We describe the pattern of SDB seen in the largest MPS I cohort described to date and determine therapies and biomarkers influencing the severity of long-term airway disease.

Methods

Therapeutic, clinical and biomarker data, including longitudinal outcome parameters from 150 sleep oximetry studies were collected in 61 MPS I (44 Hurler, 17 attenuated) patients between 6 months pre to 16 years post-treatment (median follow-up 22 months). The presence and functional nature of an immune response to ERT was determined using ELISA and a cellular uptake inhibition assay. Multivariate analysis was performed to determine significant correlators of airway disease.

Results

The incidence of SDB in our cohort is 68%, while 16% require therapeutic intervention for airway obstruction. A greater rate of progression (73%) and requirement for intervention is seen amongst ERT patients in contrast to HSCT treated individuals (24%). Multivariate analysis identifies poorer metabolic clearance, as measured by a rise in the biomarker urinary dermatan sulphate: chondroitin sulphate (DS:CS) ratio, as a significant correlator of increased presence and severity of SDB in MPS I patients (p = 0.0017, 0.008). Amongst transplanted Hurler patients, delivered enzyme (leukocyte iduronidase) at one year is significantly raised in those without SDB (p = 0.004). Cellular uptake inhibitory antibodies in ERT treated patients correlate with reduced substrate clearance and occurrence of severe SDB (p = 0.001).

Conclusion

We have identified biochemical and therapeutic factors modifying airway disease across the phenotypic spectrum in MPS I. Interventions maximising substrate reduction correlate with improved long-term SDB, while inhibitory antibodies impact on biochemical and clinical outcomes. Monitoring and tolerisation strategies should be re-evaluated to improve detection and minimise the inhibitory antibody response to ERT in MPS I and other lysosomal storage diseases. Future studies should consider the use of sleep disordered breathing as an objective parameter of clinical and metabolic improvement.

Nocturnal frontal lobe epilepsy in mucopolysaccharidosis

Nocturnal frontal lobe epilepsy (NFLE) is an epileptic syndrome that is primarily characterized by seizures with motor signs occurring almost exclusively during sleep. We describe 2 children with mucopolysaccharidosis (MPS) who were referred for significant sleep disturbance. Long term video-EEG monitoring (LT-VEEGM) demonstrated sleep-related hypermotor seizures consistent with NFLE. No case of sleep-related hypermotor seizures has ever been reported to date in MPS. However, differential diagnosis with parasomnias has been previously discussed. The high frequency of frontal lobe seizures causes sleep fragmentation, which may result in sleep disturbances observed in at least a small percentage of MPS patients. We suggest monitoring individuals with MPS using periodic LT-VEEGM, particularly when sleep disorder is present. Moreover, our cases confirm that NFLE in lysosomal storage diseases may occur, and this finding extends the etiologic spectrum of NFLE.

Mucopolysaccharidosis: Otolaryngologic findings, obstructive sleep apnea and accumulation of glucosaminoglycans in lymphatic tissue of the upper airway

OBJECTIVE

The aim of this study is to evaluate otolaryngologic problems (upper airway obstruction, obstructive sleep apnea, restriction of mouth opening, middle ear effusion, hearing and breathing problems) and their treatments on mucopolysaccharidoses (MPS) patients and to investigate accumulation of glucosaminoglycans (GAG) in the upper airway biochemically and pathologically.

METHODS

76 MPS patients were evaluated. Forty-two MPS patients underwent polysomnography (PSG) for obstructive sleep apnea (OSA). Pre- and postoperative PSG results of 18 patients were compared. The success and complications of treatments for OSA in MPS were evaluated. Biochemical and histopathological accumulation of GAG in tonsil and adenoid tissue and middle ear effusion were analyzed and compared with the control group.

RESULTS

Forty patients out of 42 tested with PSG had OSA (95%). Adenoid grade, Mallampati grade, restricted mouth opening, rate of difficult intubation were significantly different among MPS subtypes. MPS types III and IV had significantly lower Mallampati scores; type VI had significantly worse mouth opening; and type III had significantly better mouth opening and higher rate of easy intubation when compared to other MPS types. There was no significant difference between MPS subtypes according to tonsil grade, adenoid grade, rate of otitis media with effusion and OSA severity. Statistically significant difference was found between GAG accumulation in adenoid tissue and middle ear effusion of MPS and control group (p<0.05). However, GAG accumulation in tonsil was not significantly different between MPS and control group. There was a statistically significant improvement in postop Apnea-Hypopnea Index (AHI) compared to preop AHI (p<0.05).

CONCLUSIONS

Most MPS patients have airway obstruction and OSA due to adenotonsillar hypertrophy. Most of these children benefit from adenotonsillectomy, after which OSA significantly improves. They experience high recurrence rate after adenoidectomy; though this is not clinically problematic. They also suffer from conductive hearing loss due to OME, which has to be treated with ventilation tube insertion. However, such operations are usually complicated by difficult endotracheal intubation and restricted mouth opening. Sometimes tracheotomy may be necessary. Tracheotomy is also highly complicated in MPS patients. Significant accumulation of GAG in middle ear fluid and adenoid tissue is present; however, GAG appears not to accumulate in tonsillar tissue.

Characterization of pulmonary function impairments in patients with mucopolysaccharidoses--changes with age and treatment

BACKGROUND

The mucopolysaccharidoses (MPS) comprise a group of inherited lysosomal storage disorders characterized by deficiencies in enzymes catalyzing the degradation of glycosaminoglycans. Impairment of pulmonary function is an important health problem for patients with MPS. However, there are few published reports on the prevalence and severity of pulmonary dysfunction in relation to age and treatment in this disorder.

METHODS

To evaluate pulmonary function in patients with MPS, we performed spirometry in 35 patients (22 males and 13 females; 1 with MPS I, 12 with MPS II, 16 with MPS IVA, and 6 with MPS VI; mean age, 14.6 ± 5.9 years; age range, 6.4 years to 33 years). Forced vital capacity (FVC), forced expired volume in 1 sec (FEV1), FEV1 to FVC ratio (FEV1/FVC), peak expiratory flow (PEF), and mean forced expiratory flow during the middle half of FVC (FEF25-75% ) were measured.

RESULTS

Mean FVC, FEV1 , PEF, and FEF25-75% were 74.2%, 73.9%, 64.7%, and 37.1% of the predicted values, respectively. By spirometric classification, 32 patients (91%) had small airway disease (FEF25-75%  < 65%), 17 (48%) had restrictive lung disease, and 3 (9%) had obstructive lung disease. Percent predicted FVC, FEV1 , and PEF, as well as FEV1 /FVC, were all negatively correlated with age (P < 0.01), such that pubertal and post-pubertal patients had significantly lower values than younger patients. Of eight attenuated MPS II and VI patients who underwent follow-up pulmonary function testing after receiving enzyme replacement therapy (ERT) for 1.5-7.4 years, six showed improvements in % predicted FVC and five improved in % predicted FEV1 .

CONCLUSION

Our additional characterization of the types and prevalence of pulmonary function abnormalities seen in MPS patients should be useful for clinical care.

Natural history and clinical assessment of Taiwanese patients with mucopolysaccharidosis IVA

Background

Mucopolysaccharidosis IVA (MPS IVA) is a rare lysosomal storage disorder caused by N-acetylgalactosamine-6-sulfatase deficiency, which catalyzes a step in the catabolism of glycosaminoglycans, keratan sulfate and chondroitin-6-sulfate. This disease has a variable age of onset and rate of progression.

Methods

A retrospective analysis of medical records of 24 patients with MPS IVA (11 males, 13 females; current mean age ± SD, 12.6 ± 6.6 years; age range, 1.4-29.4 years) seen at 6 medical centers in Taiwan from January 1996 through June 2013 was performed.

Results

Mean ages of onset of symptoms and confirmed diagnosis were 2.0 ± 1.6 and 5.7 ± 4.5 years, respectively. The most prevalent clinical manifestations were kyphosis (100%), pectus carinatum (96%), abnormal gait (93%), striking short trunk dwarfism (92%), genu valgum (92%), and valvular heart disease (91%). Eight patients (33%) experienced at least one surgical procedure with the most common being ear tube insertion (25%), adenoidectomy (17%), tonsillectomy (13%), supraglottoplasty (13%), spinal decompression (13%), and spinal fusion (13%). The most prevalent cardiac valve abnormalities were aortic stenosis (45%) and mitral regurgitation (45%). At the time of the study, 8 out of 24 patients (33%) have died at the mean age of 17.2 ± 7.7 years.

Conclusions

An understanding of the natural history involved in MPS IVA may allow early diagnosis of the disease. All affected Taiwanese patients experienced significant functional limitations. Adequate evaluations and timely management may improve clinical outcomes and quality of life.

Assessment of sleep in children with mucopolysaccharidosis type III

Sleep disturbances are prevalent in mucopolysaccharidosis Type III (MPS III), yet there is a lack of objective, ecologically valid evidence detailing sleep quantity, quality or circadian system. Eight children with MPS III and eight age-matched typically developing children wore an actigraph for 7–10 days/nights. Saliva samples were collected at three time-points on two separate days, to permit analysis of endogenous melatonin levels. Parents completed a sleep questionnaire and a daily sleep diary. Actigraphic data revealed that children with MPS III had significantly longer sleep onset latencies and greater daytime sleep compared to controls, but night-time sleep duration did not differ between groups. In the MPS III group, sleep efficiency declined, and sleep onset latency increased, with age. Questionnaire responses showed that MPS III patients had significantly more sleep difficulties in all domains compared to controls. Melatonin concentrations showed an alteration in the circadian system in MPS III, which suggests that treatment for sleep problems should attempt to synchronise the sleep-wake cycle to a more regular pattern. Actigraphy was tolerated by children and this monitoring device can be recommended as a measure of treatment success in research and clinical practice.

Relationship of sleep to pulmonary function in mucopolysaccharidosis II

OBJECTIVE

To study the sleep characteristics, pulmonary function, and their relationships in an enzyme naive population of patients with mucopolysaccharidoses (MPS) II (Hunter syndrome).

STUDY DESIGN

The analyzed subjects (30 patients with MPS II with a median age of 9 years) had been enrolled in an MPS II natural history study and a phase I/II enzyme replacement clinical study in which they underwent standard polysomnography including spirometry and plethysmography, if cooperative. Descriptive statistics and nonparametric correlation were performed for demographic, sleep, and pulmonary function variables.

RESULTS

Median apnea-hypopnea index was 6.4, with obstructive sleep apnea observed in 27/30 subjects. Sleep architecture was characterized by diminished rapid-eye movement sleep duration (median 13%), and decline in sleep efficiency and slow-wave sleep duration in older individuals. Oxygen desaturation below 90% occurred in 26/30 subjects, and hypoventilation above 50 Torr occurred in 11/23 subjects with accurate end-tidal carbon dioxide recordings. Of 15 subjects with reliable spirometry, median forced expiratory volume in 1 second was below 80% predicted in 12/15 subjects. Forced expiratory volume in 1 second in percent-predicted was inversely related to apnea-hypopnea index and increase from baseline end-tidal carbon dioxide (P=.023, rs=-0.58), (P<.001, rs=-0.82).

CONCLUSION

Sleep in MPS II is characterized by obstructive sleep apnea, altered sleep architecture, and impaired gas exchange. Sleep disruption is related to daytime pulmonary function, thus both systems should be evaluated when sleep abnormalities are suspected.

Home sleep study characteristics in patients with mucopolysaccharidosis

BACKGROUND

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders caused by the deficiency of hydrolases involved in the degradative pathway of glycosaminoglycans. In MPS, upper airway obstruction may result from multiple causative factors which may impact severely upon morbidity and mortality.

METHODS

We evaluated upper airway obstructive disease and related clinical findings through home sleep study in 19 patients (11 with MPS VI, 4 with MPS I, 4 with MPS II) with MPS followed at Gazi University Pediatric Metabolic Unit. Patients underwent home-based sleep measurements, and sleep respiratory problems were asked in a detailed clinical history. Measurements of apnea, apnea-hypopnea index (AHI), hypopnea index, oxygen desaturation index, and minimal oxygen saturation were obtained through home sleep study.

RESULTS

For 19 children, the disorder was normal in 1, mild (AHI=1.5-5/h) in 5, moderate (AHI=5-10/h) in 2, and severe (AHI>10/h) in 11. The prevalence of OSA was 94.7 % (18/19) in patients with MPS. Snoring, witnessed apnea, pectus carinatum, and macroglossia were the main clinical findings. Echocardiograms showed evidence of pulmonary hypertension in 13 patients.

CONCLUSION

Home sleep study is a quick and accessible screening test to determine the abnormalities of breathing during sleep and enables clinicians to take necessary action for patients with severe manifestations.

Up to five years experience with 11 mucopolysaccharidosis type VI patients

Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a rare progressive metabolic disorder characterized by coarse facial features, hepatosplenomegaly, restrictive pulmonary function, cardiac abnormalities and stiff joints. The disease is caused by a deficiency of the lysosomal enzyme N-acetyl galactosamine 4-sulfatase which leads to glycosaminoglycan (GAG) storage in various tissues. It presents as a clinical spectrum with varying disease progressions and severities. While the phases I/II/III studies proved the effectiveness of enzyme-replacement therapy (ERT) with recombinant human arylsulfatase B, long-term data are still scarce. Over treatment periods ranging from 1.3 to 5.4 years, this prospective open-label follow-up study in 11 Dutch mucopolysaccharidosis type VI patients (age 2-18 years) showed that ERT had significant positive effects on cardiac-wall diameters (IVSd and LVMI), left and right shoulder flexions (p<0.001), liver size and spleen size (p<0.001), urinary GAG excretion (p<0.001), and the scales of quality of life (motor functioning and body functioning). ERT did not affect cardiac valve regurgitation or hearing function; HRQoL decreased slightly in two domains ('anxiety' and 'negative emotions'), and patients with the rapid and slow progressive forms of the disease differed with regard to baseline GAG excretion and GAG decrease during treatment. In conclusion, ERT had an effect on several clinical parameters. This effect was established in an open cohort of young mucopolysaccharidosis type VI patients.

Respiratory and sleep disorders in mucopolysaccharidosis

MPS encompasses a group of rare lysosomal storage disorders that are associated with the accumulation of glycosaminoglycans (GAG) in organs and tissues. This accumulation can lead to the progressive development of a variety of clinical manifestations. Ear, nose, throat (ENT) and respiratory problems are very common in patients with MPS and are often among the first symptoms to appear. Typical features of MPS include upper and lower airway obstruction and restrictive pulmonary disease, which can lead to chronic rhinosinusitis or chronic ear infections, recurrent upper and lower respiratory tract infections, obstructive sleep apnoea, impaired exercise tolerance, and respiratory failure. This review provides a detailed overview of the ENT and respiratory manifestations that can occur in patients with MPS and discusses the issues related to their evaluation and management.

Otolaryngologic manifestations of skeletal dysplasias in children

This article reviews some of the otolaryngologic manifestations of skeletal dysplasias. Achondroplasia is discussed most comprehensively. Skeletal dysplasias are bone and cartilage disorders that disrupt the development of the long bones, craniofacial skeleton, and vertebral column, with the most notable characteristic being short stature. Children with skeletal dysplasias have various medical problems. These children often develop head and neck manifestations of their disorders. Hearing loss, middle ear disease, and respiratory difficulties are seen in these children. Otolaryngologists must be knowledgeable about these disorders to diagnose, treat, and appropriately refer children with skeletal dysplasias.

Medical comorbidity of sleep disorders in children and adolescents

PURPOSE OF REVIEW

Sleep disorders in children and adolescents often present with various medical comorbidities. The aim of this review is to present the recent literature findings on this issue.

RECENT FINDINGS

The major medical comorbid conditions that accompany insomnia or short sleep duration in children and adolescents are obesity and metabolic syndrome, growth hormone deficiency, allergic conditions, various disorders accompanied by chronic pain, neoplasms and blood malignancies, and genetic and congenital disorders. Hypersomnia is mainly related to malignancies. Children and adolescents with obstructive sleep apnoea syndrome or sleep-disordered breathing may suffer from obesity and metabolic syndrome, polycystic ovaries, hypothyroidism, asthma, epilepsy, various ear nose throat disorders, congenital malformations or genetic conditions. Parasomnias may be comorbid with some medical conditions, but the main challenge in their evaluation is the differential diagnosis from nocturnal epileptic seizures.

SUMMARY

The co-occurrence of sleep disorders and medical conditions in childhood and adolescence is quite frequent and has an impact on general health and quality of life.

Therapy for the mucopolysaccharidoses

Better understanding of disease pathophysiology, improved supportive care and availability of disease-specific treatments for some of the mucopolysaccharidosis (MPS) disorders have greatly improved the outlook for patients with MPS disorders. Optimal management of these multisystemic disorders involves a multidisciplinary team and regular, comprehensive follow-up. Enzyme replacement therapy (ERT) is now available for MPS I (Hurler, Hurler-Scheie and Scheie syndromes) (laronidase), MPS II (Hunter syndrome) (idursulfase) and MPS VI Maroteaux-Lamy (galsulfase), and is in development for MPS IV (Morquio syndrome) and MPS VII (Sly syndrome). Benefits of ERT can include improved walking ability, improved respiration and enhanced quality of life. Haematopoietic stem cell transplantation (HSCT) can preserve cognition and prolong survival in very young children with the most severe form of MPS I, and is under investigation for several other MPS disorders. Better tissue matching techniques, improved graft-vs-host prophylaxis and more targeted conditioning regimens have improved morbidity and mortality associated with HSCT.