Upper airway obstructive disease in mucopolysaccharidoses: polysomnography, computed tomography and nasal endoscopy findings

Adenotonsillectomy for the treatment of OSA in children with mucopolysaccharidosis: A systematic review

OBJECTIVE

To study the role of adenotonsillectomy (ADT) for obstructive sleep apnea (OSA) in children with mucopolysaccharidosis (MPS).

METHODS

A systematic review were performed following the PRISMA guideline. PubMed and Embase were searched for studies regarding adenotonsillectomy for OSA in children with MPS. The MINOR Score were applied for quality assessment of the included studies.

RESULTS

Nineteen studies were eligible for inclusion: fifteen were retrospective and four prospective. A total of 1406 subjects were included. The samples size varied from 2 to 336, the male to female ratio is 1.2 and mean age varied from 2.4 to 11 years. Overall, 56.2 % (IC 95%: 53.6-58.8) of the included subjects underwent ADT. MPS I and II are the two most operated types. Three studies, including 50 children, reported improvement in polysomnographic parameters after surgery. Two authors described the duration of follow-up: 8.4 and 9.8 years, respectively.

CONCLUSIONS

More than half of children with MPS underwent ADT for the treatment of OSA, although few evidence demonstrated improvement in term of polysomnographic parameters. The two types of MPS most involved are type I and II. Considering the disease progression and anesthetic risks, multidisciplinary management may help identify the subgroup of children with MPS who benefit from ADT for the treatment of OSA.

Clinical and biochemical footprints of inherited metabolic diseases. XIII. Respiratory manifestations

At any age, respiratory manifestations are a major cause of increased morbidity and mortality of inherited metabolic diseases (IMDs). Type and severity are extremely variable, this depending on the type of the underlying disorder. Symptoms and signs originating from upper or lower airways and/or thoracic wall and/or respiratory muscles involvement can occur either at presentation or in the late clinical course. Acute respiratory symptoms can trigger metabolic decompensation which, in turn, makes airway symptoms worse, creating a vicious circle. We have identified 181 IMDs associated with various types of respiratory symptoms which were classified into seven groups according to the type of clinical manifestations affecting the respiratory system: (i) respiratory failure, (ii) restrictive lung disease, (iii) interstitial lung disease, (iv) lower airway disease, (v) upper airway obstruction, (vi) apnea, and (vii) other. We also provided a list of investigations to be performed based on the respiratory phenotypes and indicated the therapeutic strategies currently available for IMD-associated airway disease. This represents the thirteenth issue in a series of educational summaries providing a comprehensive and updated list of metabolic differential diagnoses according to system involvement.

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.

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a heterogeneous group of disorders that results in the absence or deficiency of lysosomal enzymes, leading to an inappropriate storage of glycosaminoglycans (GAGs) in various tissues of the body such as bones, cartilage, heart valves, arteries, upper airways, cornea, teeth, liver and nervous system. Clinical manifestations can become progressively exacerbated with age and affect their quality of life. Developments in advanced supportive treatment options such as enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT) may have improved patients' life span. Adult MPS patients require specialist clinical surveillance long-term. In many cases, in addition to the MPS-related health problems, they may develop age-related complications. Considering the complexity of their clinical manifestations and lack of guidelines on the management of adult MPS disorders, multispecialty and multidisciplinary teams' care is essential to diagnose and treat health problems that are likely to be encountered. This review presents non-cardiac clinical manifestations, their pathophysiology, management and long-term outcomes in adult MPS patients.

Sensory, voluntary, and motor postural control in children and adolescents with mucopolysaccharidosis

OBJECTIVES

This study aimed to investigate automatic and voluntary motor control performances, which have an important function in maintaining balance, in children and adolescents with mucopolysaccharidosis (MPS).

METHODS

The records of 70 patients were retrospectively analyzed. The results of Computerized Dynamic Posturography (CDP) performed according to the age and development of the individuals were examined. The results of 10 children and adolescents with MPS (mean age: 9.43 ranging from 6 to 14; four males and six females) who completed the sensory analysis, Weight-Bearing Squat Test, and Adaptation Test were retrieved from the database of the CDP. Nine healthy children and adolescents with typical development (mean age: 9.63 ranging from 6 to 14; four males and five females) were included as the control group.

RESULTS

In the sensory analysis test, there was a statistically significant difference between the two groups in the visual ratio parameter. In the adaptation test, there was a statistically significant difference between the two groups in the toes up and toes down trials. There was no statistically significant difference between the groups in the Weight-Bearing Squat test at 0° knee extension and various knee flexions.

CONCLUSIONS

Children and adolescents with MPS should be directed to the appropriate exercise and therapy programs to develop postural and balance control, which have a significant effect on their quality of life and the ability to independently perform daily activities of living. In addition to routine hearing assessments for patients with MPS, other objective tests used in the differential diagnosis of balance and vestibular system should also be implemented.

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.

Imaging features of mucopolysaccharidoses in the head and neck

Ear, Nose and Throat (ENT) involvement by mucopolysaccharidoses is very common, affecting over 90% of patients, and occurs early in the course of the disease. Airway narrowing secondary to glycosaminoglycan deposition results in greatly increased morbidity, mortality and risk of anesthetic complications in these patients. Macroglossia, restricted mouth opening, tracheobronchomalacia, adenotonsillar hypertrophy along with other factors such as a short, rigid and unstable cervical spine, cardiac disease and increased susceptibility to respiratory infections result in a high perioperative mortality and morbidity. Imaging is most beneficial for evaluation of the airway, in particular in patients with obstructive symptoms and prior to intubation. We review the ENT manifestations of mucopolysaccharidoses including airway involvement, otological, oral and dental complications. 3-D reconstructions of the trachea, which is routinely captured on CT imaging of the spine, can be of great value for planning intubation in this patient population.

Report on advances for pediatricians in 2018: allergy, cardiology, critical care, endocrinology, hereditary metabolic diseases, gastroenterology, infectious diseases, neonatology, nutrition, respiratory tract disorders and surgery

This review reported notable advances in pediatrics that have been published in 2018. We have highlighted progresses in allergy, cardiology, critical care, endocrinology, hereditary metabolic diseases, gastroenterology, infectious diseases, neonatology, nutrition, respiratory tract disorders and surgery. Many studies have informed on epidemiologic observations. Promising outcomes in prevention, diagnosis and treatment have been reported. We think that advances realized in 2018 can now be utilized to ameliorate patient care.

Respiratory manifestations in inherited metabolic diseases: 6-year single-center experience

OBJECTIVES

We aimed to call attention to respiratory system manifestations which occur in the course of many inherited metabolic diseases (IMD), and present as the leading cause of death.

MATERIALS AND METHODS

We retrospectively reviewed the diagnosis, treatment, and outcome of patients evaluated at our hospital between June 2012 and June 2018 with a diagnosis of IMD and accompanying respiratory manifestations.

RESULTS

A total of 50 children (29 [58%] male, 21 [42%] female) with IMD and respiratory manifestations were defined. Disorders of intracellular metabolism (n = 33, 66%) formed the majority, followed by intoxication type metabolic disorders (n = 9, 18%) and energy metabolism disorders (n = 8, 16%). The most frequent respiratory symptoms were snoring (20, 40%), tachypnea (16, 32%) and wheezing (14, 28%). Physical examination findings were signs of respiratory distress (n = 28, 56%), crackles (n = 24, 48%), thoracic deformity (n = 23, 46%), decreased breath sounds (n = 17, 34%), rhonchus (n = 17, 34%), wheezing (n = 17, 34%) and stridor (n = 10, 20%). Major respiratory manifestations were chronic airway aspiration (n = 23, 46%), upper airway obstruction (n = 23, 46%), and recurrent pneumonia (n = 18, 36%). Twenty-three 23 patients (46%) experienced endotracheal intubation, 9 patients (18%) required whole-house mechanical ventilation and tonsilloadenoidectomy was performed in 7 patients (14%). Overall survival rate was 70% (n = 35) in a median follow-up period of 2.36 (0.05-5.86) years.

CONCLUSIONS

Respiratory system manifestations of IMD strongly relate with increased morbidity and mortality. Therefore, prompt diagnosis and correct intervention of respiratory complications with a multidisciplinary team including pediatric metabolic diseases specialists, pulmonologists, otorhinolaryngologists, physiotherapists, and anesthesiologists are crucial to prevent progression and irreversible damage.

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.

The characterisation of pulmonary function in patients with mucopolysaccharidoses IVA: A longitudinal analysis

Introduction

Mucopolysaccharidosis (MPS) type IVA is a rare, autosomal recessive lysosomal storage disease causing substrate accumulation in various organs and tissues. MPS IVA is associated with both obstructive and restrictive airway disease, with the former often resulting in sleep disordered breathing (SDB). Respiratory failure is a primary cause of death in this condition. The aim of this study was to characterise and catalogue the long-term respiratory changes in patients with MPS IVA treated with, or without, enzyme replacement therapy (ERT).

Methods

In this retrospective, longitudinal, repeated-measures cohort study, descriptive statistics and non-parametric correlation were performed for demographic, respiratory function and oximetry variables over a study period from January 2009 to December 2018. Composite clinical endpoints used in this study for evaluating pulmonary function included spirometry variables (FEV₁, FEV₁ [%Pred] FVC, FVC [%Pred] and FEV1/FVC), oximetry variables (median %Spo2, ODI 3%, mean nadir 3%, ODI 4%, mean nadir 4% and min dip SpO2 [%]) and 6MWT to assess functional exercise capacity and thus integrated cardiopulmonary function.

Results

Sequential spirometry and oximetry values were collected from 16 patients, of which 13/16 were ERT treated. In general, during the study period there was a global reduction in static spirometry values in all subjects, as well as cardiorespiratory function as assessed by the 6MWT, with the decline being delayed in the ERT group. Oximetry changed to a minor degree over time in the ERT group, whereas it declined in the non-ERT group. FEV₁, FVC [%predicted] and ODI 3% exhibited a strong, combined positive correlation (r 0.74–95% CI 0.61 to 0.83; p < .0001). Non-invasive ventilation (NIV) and adenotonsillectomy appeared more effective in the ERT group, either improving pulmonary function or attenuating deterioration.

Conclusions

Whilst spirometry values showed a gradual decline across all groups, oximetry showed modest improvement in respiratory function. The amalgamation of FEV₁, FVC [%predicted] and ODI 3% appeared predictive of changes in respiratory function in this study, suggestive as being composite endpoints for monitoring disease progression as well as guiding response to ERT in MPS IVA patients.

Molecular Pathways and Respiratory Involvement in Lysosomal Storage Diseases

Lysosomal storage diseases (LSD) include a wide range of different disorders with variable degrees of respiratory system involvement. The purpose of this narrative review is to treat the different types of respiratory manifestations in LSD, with particular attention being paid to the main molecular pathways known so far to be involved in the pathogenesis of the disease. A literature search was conducted using the Medline/PubMed and EMBASE databases to identify studies, from 1968 through to November 2018, that investigated the respiratory manifestations and molecular pathways affected in LSD. Pulmonary involvement includes interstitial lung disease in Gaucher’s disease and Niemann-Pick disease, obstructive airway disease in Fabry disease and ventilatory disorders with chronic respiratory failure in Pompe disease due to diaphragmatic and abdominal wall muscle weakness. In mucopolysaccharidosis and mucolipidoses, respiratory symptoms usually manifest early in life and are secondary to anatomical malformations, particularly of the trachea and chest wall, and to accumulation of glycosaminoglycans in the upper and lower airways, causing, for example, obstructive sleep apnea syndrome. Although the molecular pathways involved vary, ranging from lipid to glycogen and glycosaminoglycans accumulation, some clinical manifestations and therapeutic approaches are common among diseases, suggesting that lysosomal storage and subsequent cellular toxicity are the common endpoints.

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.

Enzyme replacement therapy: efficacy and limitations

Enzyme replacement therapy (ERT) is available for mucopolysaccharidosis (MPS) I, MPS II, MPS VI, and MPS IVA. The efficacy of ERT has been evaluated in clinical trials and in many post-marketing studies with a long-term follow-up for MPS I, MPS II, and MPS VI. While ERT is effective in reducing urinary glycosaminoglycans (GAGs) and liver and spleen volume, cartilaginous organs such as the trachea and bronchi, bones and eyes are poorly impacted by ERT probably due to limited penetration in the specific tissue. ERT in the present formulations also does not cross the blood–brain barrier, with the consequence that the central nervous system is not cured by ERT. This is particularly important for severe forms of MPS I and MPS II characterized by cognitive decline. For severe MPS I patients (Hurler), early haematopoietic stem cell transplantation is the gold standard, while still controversial is the role of stem cell transplantation in MPS II. The use of ERT in patients with severe cognitive decline is the subject of debate; the current position of the scientific community is that ERT must be started in all patients who do not have a more effective treatment. Neonatal screening is widely suggested for treatable MPS, and many pilot studies are ongoing. The rationale is that early, possibly pre-symptomatic treatment can improve prognosis. All patients develop anti-ERT antibodies but only a few have drug-related adverse reactions. It has not yet been definitely clarified if high-titre antibodies may, at least in some cases, reduce the efficacy of ERT.

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.

Correlation Between Flexible Fiberoptic Laryngoscopic and Polysomnographic Findings in Patients with Mucopolysaccharidosis Type VI

This study aimed to compare flexible fiberoptic laryngoscopy (FFL) and polysomnography (PSG) findings in patients with mucopolysaccharidosis (MPS) type VI and to describe upper airway anatomical findings and abnormal PSG results in these patients. In this cross-sectional study, all MPS VI patients followed up at the genetic division of a hospital in southern Brazil were included. Overnight PSG was performed, and the results were classified as normal or mildly, moderately, or severely abnormal. FFL was performed between 7 days before and 7 days after PSG. FFL findings were classified as (1) no obstruction, (2) mild obstruction, (3) moderate obstruction, or (4) severe obstruction of the airways, using the highest score obtained in all the regions.Eleven patients with MPS VI were included. FFL detected severe airway obstruction in eight (72.7%) patients, moderate obstruction in two (18.2%), and mild obstruction in one (9.1%). PSG revealed obstructive sleep apnea syndrome (OSAS) in nine (81.8%) patients. Among these, mild OSAS was observed in five (45.5%) patients, moderate OSAS in three (27.2%), and severe OSAS in one (9.1%). Moderate to severe hypertrophy of the nasal turbinates was found in 81.8% of the patients, and 64% had severe infiltration in the supraglottic region. There was no association between FFL and PSG findings (p = 0.454; κ = -0.09; 95%CI = -0.34 to 0.17), indicating no agreement between the two methods. In the present study, all patients with MPS showed some degree of airway obstruction. We suggest performing PSG in MPS patients to determine disease severity.

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.

Adenoids of patients with mucopolysaccharidoses demonstrate typical alterations

OBJECTIVE

Tonsillar hypertrophy caused by the progressive accumulation of partially degraded glycosaminoglycans (GAGs) within the cells is a typical symptom in patients with mucopolysaccharidoses (MPS). We studied the tissue of adenoids and tonsils of patients suffering from MPS with special regard to characteristic morphological features serving as possible markers for diagnosis.

METHODS

Adenoids of 87 patients and tonsils of 4 patients with MPS (2 patients with MPS I, 7 MPS II, 5 MPS IV and 10 MPS VI and 63 controls) and controls were examined. Examinations were repeated in a blinded manner by two pathologists.

RESULTS

The key feature observed was a subepithelial "clearing" on scanning magnification, induced by perivascular accumulation of histiocytoid cell forms. Similar agglomerates could sometimes be found at the base of lymphoid follicles. In the blinded assessment a specificity of 92% (100% for adenoids) and a sensitivity of 100% were achieved. The inter-observer-consistency was 92% (100% for adenoids). In tonsillectomy specimens marked subepithelilal fibrosis can lead to a false-negative evaluation.

CONCLUSIONS

Qualified histological examination could be an option for early diagnosis of MPS.

Intraoperative long range optical coherence tomography as a novel method of imaging the pediatric upper airway before and after adenotonsillectomy

BACKGROUND/OBJECTIVES

While upper airway obstruction is a common problem in the pediatric population, the first-line treatment, adenotonsillectomy, fails in up to 20% of patients. The decision to proceed to surgery is often made without quantitative anatomic guidance. We evaluated the use of a novel technique, long-range optical coherence tomography (LR-OCT), to image the upper airway of children under general anesthesia immediately before and after tonsillectomy and/or adenoidectomy. We investigated the feasibility of LR-OCT to identify both normal anatomy and sites of airway narrowing and to quantitatively compare airway lumen size in the oropharyngeal and nasopharyngeal regions pre- and post-operatively.

METHODS

46 children were imaged intraoperatively with a custom-designed LR-OCT system, both before and after adenotonsillectomy. These axial LR-OCT images were both rendered into 3D airway models for qualitative analysis and manually segmented for quantitative comparison of cross-sectional area.

RESULTS

LR-OCT images demonstrated normal anatomic structures (base of tongue, epiglottis) as well as regions of airway narrowing. Volumetric rendering of pre- and post-operative images clearly showed regions of airway collapse and post-surgical improvement in airway patency. Quantitative analysis of cross-sectional images showed an average change of 70.52mm(2) (standard deviation 47.87mm(2)) in the oropharynx after tonsillectomy and 105.58mm(2) (standard deviation 60.62mm(2)) in the nasopharynx after adenoidectomy.

CONCLUSIONS

LR-OCT is an emerging technology that rapidly generates 3D images of the pediatric upper airway in a feasible manner. This is the first step toward development of an office-based system to image awake pediatric subjects and thus better identify loci of airway obstruction prior to surgery.

Comparison of treatment modalities in syndromic children with obstructive sleep apnea--a randomized cohort study

INTRODUCTION

Obstructive Sleep Apnea (OSA) is a common medical problem in adults that is becoming increasingly recognized in children. It occurs in the pediatric age group, from newborns to teens. More recently, many specialists have estimated OSA prevalence to be between 5 and 6%. However, in syndromic children, the prevalence of OSA can be from 50 to 100%, having a significant effect on their Quality-of-Life. As they are a challenging population for management, it is essential to evaluate them thoroughly before planning appropriate intervention.

OBJECTIVE

To compare the efficacy of Adenotonsillectomy (T&A) and Continuous Positive Airway Pressure (CPAP) in syndromic children [Down syndrome (DS) and Mucopolysaccharidoses (MPS)] with Obstructive Sleep Apnea (OSA).

MATERIALS AND METHODS

In a prospective, randomized, cohort comparative study, 124 syndromic children (DS and MPS) aged between 6 and 12 years were recruited from a private MPS support group and the Down Syndrome Society, Chennai. A standard assessment was performed on all children who entered the study including a full overnight Polysomnogram (PSG), Epworth Sleepiness Scale-Children (ESS-C) and Quality-of-Life (QOL) tool OSA-18. The children with positive PSG who consented for the study (n = 80) were randomly distributed to two groups, T&A group & CPAP group. The children were followed up with repeat PSG, clinical evaluation, ESS-C and Quality-of-Life (QOL) tool OSA-18 for a period of 1 year.

OBSERVATION AND RESULTS

Follow-up was available for 73 syndromic children. Both the groups, T&A group and CPAP group, showed statistically significant (p < 0.05) improvement in Apnea-Hypoapnea Index (AHI), ESS-C, QOL from the intervention. In our study, T&A showed equal outcome compared to CPAP. The contrasting feature between the two groups was that CPAP use gave immediate sustained improvement while T&A gave gradual progressive improvement of symptoms over a period of 1 year.

CONCLUSION

On average, T&A gives equal outcomes as CPAP and it can be suggested as a first-line treatment in this group of syndromic children.

CT and endoscopic evaluation of larynx and trachea in mucopolysaccharidoses

BACKGROUND

Mucopolysaccharidoses (MPSs) are lysosomal storage disorders caused by lysosomal enzyme deficiencies that result in systemic accumulation of glycosaminoglycans (GAGs). Accumulation of GAGs in the upper airway can lead to respiratory failure. The aim of this study was to investigate changes of the airway by flexible endoscopy and CT.

METHODS

Thirty-five patients aging from 2 to 16 years (mean: 9.2±4.4 years) participated in this study. The majority had MPS I (n=5) or MPS II (n=25). The shape of the trachea and the cross-sectional trachea surface area (TSA) was determined at the Th1 and Th2 levels. Airway obstruction was evaluated from endoscopic findings and classified into 3 grades (Grades 0, 1, and 2). Forty-five patients in the control group who underwent tracheal CT for other conditions were retrospectively selected from the database.

RESULTS

Tracheal morphology was abnormal in 50-60%, which showed a transversely collapsing narrow trachea. Tracheal deformity was severe in MPS II and MPS IV. The mean TSA of the MPS patients was 55.5±29.0 mm(2) at Th1 and 61.4±29.0 mm(2) at Th2, while that of the control group was 90.1±41.9 mm(2) and 87.9±39.3 mm(2), respectively. Respiratory distress was noted in 15 of the 35 patients, among whom 7 patients showed tracheal deformity and 7 patients had laryngeal redundancy. Three patients had no abnormalities of the larynx or trachea, so other factors such as pharyngeal stenosis or lower airway stenosis might have contributed to their respiratory distress.

CONCLUSION

CT and flexible endoscopy allow quantitative and morphological evaluation of airway narrowing, which is beneficial for airway management in MPS children.

Dentomaxillofacial manifestations of mucopolysaccharidosis VI: clinical and imaging findings from two cases, with an emphasis on the temporomandibular joint

OBJECTIVES

Using a clinical survey, panoramic, cone-beam computed tomography (CBCT), and magnetic resonance (MR) imaging, this study was conducted to ascertain primary maxillofacial abnormalities in patients with mucopolysaccharidosis VI (MPS VI).

STUDY DESIGN

Two patients previously diagnosed with MPS VI underwent clinical and imaging surveys (panoramic radiographs, CBCT, and MR imaging).

RESULTS

Jaw involvement was present in all patients. The most prevalent findings were enlarged marrow spaces, osteopenia, dentigerous cyst-like follicles, effacement of the jaw structures, and osteosclerosis. This is the first study to describe temporomandibular joint (TMJ) involvement for MPS VI.

CONCLUSIONS

CBCT and MR imaging were needed to observe features that were not clear in conventional radiographs. Both patients reported symptoms in the TMJ and demonstrated involvement during their examinations. A multicenter study is necessary to better document maxillofacial involvement in MPS VI.

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.

Early initiation of enzyme replacement therapy for the mucopolysaccharidoses

The mucopolysaccharidoses (MPS), a group of rare genetic disorders caused by defects in glycosaminoglycan (GAG) catabolism, are progressive, multi-systemic diseases with a high burden of morbidity. Enzyme replacement therapy (ERT) is available for MPS I, II, and VI, and may improve walking ability, endurance, and pulmonary function as evidenced by data from pivotal trials and extension studies. Despite these demonstrable benefits, cardiac valve disease, joint disease, and skeletal disease, all of which cause significant morbidity, do not generally improve with ERT if pathological changes are already established. Airway disease improves, but usually does not normalize. These limitations can be well understood by considering the varied functions of GAG in the body. Disruption of GAG catabolism has far-reaching effects due to the triggering of secondary pathogenic cascades. It appears that many of the consequences of these secondary pathogenic events, while they may improve on treatment, cannot be fully corrected even with long-term exposure to enzyme, thereby supporting the treatment of patients with MPS before the onset of clinical disease. This review examines the data from clinical trials and other studies in human patients to explore the limits of ERT as currently used, then discusses the pathophysiology, fetal tissue studies, animal studies, and sibling reports to explore the question of how early to treat an MPS patient with a firm diagnosis. The review is followed by an expert opinion on the rationale for and the benefits of early treatment.

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.

Imaging findings of mucopolysaccharidoses: a pictorial review

Introduction

Mucopolysaccharidosis (MPS) represent a heterogeneous group of inheritable lysosomal storage diseases in which the accumulation of undegraded glycosaminoglycans (GAGs) leads to progressive damage of affected tissues. The typical symptoms include organomegaly, dysostosis multiplex, mental retardation and developmental delay. Definitive diagnosis is usually possible through enzymatic assays of the defective enzyme in cultured fibroblasts or leukocytes.

Imaging findings

Radiological and neuroradiological findings are reported. The most important neuroradiological features include abnormal signal intensity in the white matter, dilatation of periventricular spaces, widening of cortical sulci, brain atrophy, enlargement of extraventricular spaces and spinal cord compression. With reference to the skeletal system, most important radiological findings include multiplex dysostosis, which is represented by several bone malformations found in the skull, hands, legs, arms and column. The abnormal storage of GAGs leads to liver and spleen enlargement; it also damages cartilage layers and synovial recesses in the joints.

Conclusion

The aim of this pictorial essay is to describe the imaging findings of MPS, represented by skeletal and neurological features; skeletal X-ray and MR allow an assessment of the severity of disease, to plan medical and surgical therapy and to evaluate response to treatment.

Teaching Points

• To describe the imaging findings common to different types of MPS.

• To describe multiplex dysostosis encountered in the axial and appendicular skeleton.

• To evaluate neuroradiological features of MPS, including brain abnormal signal intensity and atrophy.

• To evaluate important otorhinolaryngological problems, such as otitis media and airways obstruction.

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.

Hypertransaminasemia and fatal lung disease: a case report

Glycogenosis type II (Pompe disease) is a rare autosomal recessive genetic disorder caused by mutations in the gene encoding the lysosomal enzyme acid α-glucosidase. The classic form is characterized by severe cardiac involvement, generalized hypotonia and exitus early in life. Presenting symptoms and signs of the disease may be neglected or underestimated, thus delaying the diagnosis. Respiratory manifestations mainly occur because of respiratory muscle weakness. However, additional mechanisms can favor the development of pulmonary complications that result in fatal respiratory failure. We herein describe a case of an infant with glycogenosis type II presenting with hepatomegaly and hypertransaminasemia, who rapidly developed fatal lung disease.

A case of galactosemia misdiagnosed as cow's milk intolerance

We report on a female patient affected by galactosemia in whom the diagnosis was obscured by the concomitant presence of manifestations suggesting a cow's milk intolerance. This case exemplifies the problems in reaching a correct diagnosis in patients with metabolic diseases.

Analysis of the upper airway by the acoustic reflection method in children with mucopolysaccharidosis

BACKGROUND

Upper airway obstruction is common in children with mucopolysaccharidosis. The acoustic reflection method is a noninvasive technique that can analyze the caliber of the upper airways. The aim of the study was to evaluate the feasibility of the acoustic reflection method in children with mucopolysaccharidosis, and to compare the characteristics of the upper airways evaluated by the acoustic reflection method in patients with mucopolysaccharidosis to matched healthy counterparts.

METHODS

Open, single center, prospective, study.

RESULTS

Accurate acoustic reflection measurements could be obtained in 7 of 10 patients (mean age: 10.4 ± 3.9 years; mucopolysaccharidosis type II (n = 3); type IV (n = 2), type VI (n = 1), and fucosidosis (n = 1)). The mean minimum cross-sectional area was lower in mucopolysaccharidosis patients (1.6 ± 0.3 cm(2) ) as compared to 14 healthy counterparts (1.8 ± 0.3 cm(2); P = 0.03). The mean resistance of the airways was significantly higher in the MPS group (7.9 ± 1.8 cmH(2) O l(-1) sec) as compared to the controls (5.5 ± 1.2 cmH(2) O l(-1) sec; P = 0.006).

CONCLUSION

This study is the first to analyze the upper airways by the noninvasive acoustic reflection method in children with mucopolysaccharidosis. Due to a lack of cooperation, reliable measurements could only be obtained in 70% of a selected group of patients. Children with mucopolysaccharidosis have significant upper airway obstruction as assessed by the reduction of the minimal cross-sectional area of the upper airways and the increase in airway resistance.

Executive summary of respiratory indications for polysomnography in children: an evidence-based review

OBJECTIVE

This comprehensive, evidence-based review provides a systematic analysis of the literature regarding the validity, reliability, and clinical utility of polysomnography for characterizing breathing during sleep in children. Findings serve as the foundation of practice parameters regarding respiratory indications for polysomnography in children.

METHODS

A task force of content experts performed a systematic review of the relevant literature and graded the evidence using a standardized grading system. Two hundred forty-three evidentiary papers were reviewed, summarized, and graded. The analysis addressed the operating characteristics of polysomnography as a diagnostic procedure in children and identified strengths and limitations of polysomnography for evaluation of respiratory function during sleep.

RESULTS

The analysis documents strong face validity and content validity, moderately strong convergent validity when comparing respiratory findings with a variety of relevant independent measures, moderate-to-strong test-retest validity, and limited data supporting discriminant validity for characterizing breathing during sleep in children. The analysis documents moderate-to-strong test-retest reliability and interscorer reliability based on limited data. The data indicate particularly strong clinical utility in children with suspected sleep related breathing disorders and obesity, evolving metabolic syndrome, neurological, neurodevelopmental, or genetic disorders, and children with craniofacial syndromes. Specific consideration was given to clinical utility of polysomnography prior to adenotonsillectomy (AT) for confirmation of obstructive sleep apnea syndrome. The most relevant findings include: (1) recognition that clinical history and examination are often poor predictors of respiratory polygraphic findings, (2) preoperative polysomnography is helpful in predicting risk for perioperative complications, and (3) preoperative polysomnography is often helpful in predicting persistence of obstructive sleep apnea syndrome in patients after AT. No prospective studies were identified that address whether clinical outcome following AT for treatment of obstructive sleep apnea is improved in association with routine performance of polysomnography before surgery in otherwise healthy children. A small group of papers confirm the clinical utility of polysomnography for initiation and titration of positive airway pressure support.

CONCLUSIONS

Pediatric polysomnography shows validity, reliability, and clinical utility that is commensurate with most other routinely employed diagnostic clinical tools or procedures. Findings indicate that the "gold standard" for diagnosis of sleep related breathing disorders in children is not polysomnography alone, but rather the skillful integration of clinical and polygraphic findings by a knowledgeable sleep specialist. Future developments will provide more sophisticated methods for data collection and analysis, but integration of polysomnographic findings with the clinical evaluation will represent the fundamental diagnostic challenge for the sleep specialist.

Practice parameters for the respiratory indications for polysomnography in children

BACKGROUND

There has been marked expansion in the literature and practice of pediatric sleep medicine; however, no recent evidence-based practice parameters have been reported. These practice parameters are the first of 2 papers that assess indications for polysomnography in children. This paper addresses indications for polysomnography in children with suspected sleep related breathing disorders. These recommendations were reviewed and approved by the Board of Directors of the American Academy of Sleep Medicine.

METHODS

A systematic review of the literature was performed, and the American Academy of Neurology grading system was used to assess the quality of evidence. RECOMMENDATIONS FOR PSG USE: 1. Polysomnography in children should be performed and interpreted in accordance with the recommendations of the AASM Manual for the Scoring of Sleep and Associated Events. (Standard) 2. Polysomnography is indicated when the clinical assessment suggests the diagnosis of obstructive sleep apnea syndrome (OSAS) in children. (Standard) 3. Children with mild OSAS preoperatively should have clinical evaluation following adenotonsillectomy to assess for residual symptoms. If there are residual symptoms of OSAS, polysomnography should be performed. (Standard) 4. Polysomnography is indicated following adenotonsillectomy to assess for residual OSAS in children with preoperative evidence for moderate to severe OSAS, obesity, craniofacial anomalies that obstruct the upper airway, and neurologic disorders (e.g., Down syndrome, Prader-Willi syndrome, and myelomeningocele). (Standard) 5. Polysomnography is indicated for positive airway pressure (PAP) titration in children with obstructive sleep apnea syndrome. (Standard) 6. Polysomnography is indicated when the clinical assessment suggests the diagnosis of congenital central alveolar hypoventilation syndrome or sleep related hypoventilation due to neuromuscular disorders or chest wall deformities. It is indicated in selected cases of primary sleep apnea of infancy. (Guideline) 7. Polysomnography is indicated when there is clinical evidence of a sleep related breathing disorder in infants who have experienced an apparent life-threatening event (ALTE). (Guideline) 8. Polysomnography is indicated in children being considered for adenotonsillectomy to treat obstructive sleep apnea syndrome. (Guideline) 9. Follow-up PSG in children on chronic PAP support is indicated to determine whether pressure requirements have changed as a result of the child's growth and development, if symptoms recur while on PAP, or if additional or alternate treatment is instituted. (Guideline) 10. Polysomnography is indicated after treatment of children for OSAS with rapid maxillary expansion to assess for the level of residual disease and to determine whether additional treatment is necessary. (Option) 11. Children with OSAS treated with an oral appliance should have clinical follow-up and polysomnography to assess response to treatment. (Option) 12. Polysomnography is indicated for noninvasive positive pressure ventilation (NIPPV) titration in children with other sleep related breathing disorders. (Option) 13. Children treated with mechanical ventilation may benefit from periodic evaluation with polysomnography to adjust ventilator settings. (Option) 14. Children treated with tracheostomy for sleep related breathing disorders benefit from polysomnography as part of the evaluation prior to decannulation. These children should be followed clinically after decannulation to assess for recurrence of symptoms of sleep related breathing disorders. (Option) 15. Polysomnography is indicated in the following respiratory disorders only if there is a clinical suspicion for an accompanying sleep related breathing disorder: chronic asthma, cystic fibrosis, pulmonary hypertension, bronchopulmonary dysplasia, or chest wall abnormality such as kyphoscoliosis. (Option) RECOMMENDATIONS AGAINST PSG USE: 16. Nap (abbreviated) polysomnography is not recommended for the evaluation of obstructive sleep apnea syndrome in children. (Option) 17. Children considered for treatment with supplemental oxygen do not routinely require polysomnography for management of oxygen therapy. (Option)

CONCLUSIONS

Current evidence in the field of pediatric sleep medicine indicates that PSG has clinical utility in the diagnosis and management of sleep related breathing disorders. The accurate diagnosis of SRBD in the pediatric population is best accomplished by integration of polysomnographic findings with clinical evaluation.

Polysomnographic characteristics in patients with mucopolysaccharidoses

To evaluate the prevalence of obstructive sleep apnea (OSA) and to clarify sleep characteristics in patients with mucopolysaccharidoses (MPS), we performed overnight polysomnographic studies in 24 patients (22 males and 2 females; 3 with MPS I, 15 with MPS II, 1 with MPS III, 1 with MPS IV, and 4 with MPS VI; mean age, 10.8 ± 6.0 years; age range, 2.0-23.7 years; 2 patients ≥18 years of age). The nadir arterial oxygen saturation (SaO(2) ) was 74.5 ± 12.3%, and the average percentage of sleep time with an SaO(2) of <95% was 39.4%. The percentages of total sleep time spent in sleep stages N1, N2, N3, and R were 18.6 ± 10.8%, 50.3 ± 7.6%, 14.8 ± 8.1%, and 15.3 ± 4.6%, respectively. The respiratory disturbance index (RDI) was 21.8 ± 20.4/hr, and obstructive apnea-hypopnea index (OAHI) and central apnea index were 21.4 ± 19.9/hr and 0.4 ± 0.6/hr, respectively. The desaturation index was 17.6 ± 17.8/hr. All patients had some degree of OSA. For 22 children, the disorder was mild (OAHI 1.5-5) in 2, moderate (OAHI 5-10) in 7, and severe (OAHI > 10) in 13. Two patients with MPS II who received enzyme replacement therapy had reductions in RDI after treatment (38.9-10.8 and 3.5-2.0, respectively). The prevalence of moderate to severe OSA was 88% (21/24) in patients with MPS. The overnight polysomnography will help to determine the abnormalities of breathing during sleep more precisely and urge the clinicians to take necessary action for patients with severe manifestations.

Sleep-related breathing in children with mucopolysaccharidosis

BACKGROUND

The mucopolysaccharidoses (MPSs), a group of genetic lysosomal storage disorders, are associated with significant morbidity. Secondarily to specific associated anatomical abnormalities, MPS is associated with sleep disordered breathing (SDB), specifically obstructive sleep apnoea (OSA) that may confer additional morbidity. Few studies have examined SDB in children with MPS using full polysomnography (PSG) and thus the exact prevalence and severity of SDB is unknown. Further, successful treatments for SDB in this population have not been explored.

OBJECTIVES

This study evaluated both SDB and the efficacy of treatments offered to children with MPS using PSG data.

PATIENTS AND METHODS

A retrospective chart review was conducted on all children with MPS and a history of suspected OSA who were referred to the Hospital for Sick Children, Toronto. Both baseline and follow up treatment PSG data were analysed. PSG data recorded included obstructive apnoea-hypopnoea index (OAHI) and central apnoea index (CAI).

RESULTS

Fourteen patients (10 male) underwent a baseline PSG. Three of 14 children on ERT were excluded from the main analyses. The median (range) baseline parameters of the population (n = 11) were recorded. The age was 5.2 years (0.8-17.8) and the body mass index (BMI) was 19.9 (13.7-22.2). The OAHI was 6.6 (0.0-54.8); the CAI was 0.6 (0.0-2.6). Seven of 11 (64%) had evidence for OSA and 3/7 children were classified as having severe OSA (OAHI > 10). Of these, 5/7 children underwent treatment for OSA with 3/5 children showing a significant reduction in their OAHI. Further, the 2 patients on ERT therapy with OSA were also both successfully treated.

CONCLUSIONS

Children with MPS have a high prevalence of significant OSA and thus should be carefully screened for OSA using full polysomnography and treated accordingly.

Mucopolysaccharidosis I: management and treatment guidelines

OBJECTIVE

Disease management for mucopolysaccharidosis type I has been inconsistent because of disease rarity (approximately 1 case per 100,000 live births), phenotypic heterogeneity, and limited therapeutic options. The availability of hematopoietic stem cell transplantation and the recent introduction of enzyme replacement therapy for mucopolysaccharidosis I necessitate the establishment of system-specific management guidelines for this condition.

METHODS

Twelve international experts on mucopolysaccharidosis I met in January 2003 to draft management and treatment guidelines for mucopolysaccharidosis I. Initial guidelines were revised and updated in 2008, on the basis of additional clinical data and therapeutic advances. Recommendations are based on our extensive clinical experience and a review of the literature.

RESULTS

All patients with mucopolysaccharidosis I should receive a comprehensive baseline evaluation, including neurologic, ophthalmologic, auditory, cardiac, respiratory, gastrointestinal, and musculoskeletal assessments, and should be monitored every 6 to 12 months with individualized specialty assessments, to monitor disease progression and effects of intervention. Patients are best treated by a multidisciplinary team. Treatments consist of palliative/supportive care, hematopoietic stem cell transplantation, and enzyme replacement therapy. The patient's age (>2 years or < or =2 years), predicted phenotype, and developmental quotient help define the risk/benefit profile for hematopoietic stem cell transplantation (higher risk but can preserve central nervous system function) versus enzyme replacement therapy (low risk but cannot cross the blood-brain barrier).

CONCLUSION

We anticipate that provision of a standard of care for the treatment of patients with mucopolysaccharidosis I will optimize clinical outcomes and patients' quality of life.