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

Long term follow-up after haematopoietic stem cell transplantation for mucopolysaccharidosis type I-H: a retrospective study of 51 patients

Mucopolysaccharidosis type I-H (MPS I-H) is a rare lysosomal storage disorder caused by α-L-Iduronidase deficiency. Early haematopoietic stem cell transplantation (HSCT) is the sole available therapeutic option to preserve neurocognitive functions. We report long-term follow-up (median 9 years, interquartile range 8-16.5) for 51 MPS I-H patients who underwent HSCT between 1986 and 2018 in France. 4 patients died from complications of HSCT and one from disease progression. Complete chimerism and normal α-L-Iduronidase activity were obtained in 84% and 71% of patients respectively. No difference of outcomes was observed between bone marrow and cord blood stem cell sources. All patients acquired independent walking and 91% and 78% acquired intelligible language or reading and writing. Intelligence Quotient evaluation (n = 23) showed that 69% had IQ ≥ 70 at last follow-up. 58% of patients had normal or remedial schooling and 62% of the 13 adults had good socio-professional insertion. Skeletal dysplasia as well as vision and hearing impairments progressed despite HSCT, with significant disability. These results provide a long-term assessment of HSCT efficacy in MPS I-H and could be useful in the evaluation of novel promising treatments such as gene therapy.

Mucopolysaccharidosis Type I: Current Treatments, Limitations, and Prospects for Improvement

Mucopolysaccharidosis type I (MPS I) is a lysosomal disease, caused by a deficiency of the enzyme alpha-L-iduronidase (IDUA). IDUA catalyzes the degradation of the glycosaminoglycans dermatan and heparan sulfate (DS and HS, respectively). Lack of the enzyme leads to pathologic accumulation of undegraded HS and DS with subsequent disease manifestations in multiple organs. The disease can be divided into severe (Hurler syndrome) and attenuated (Hurler-Scheie, Scheie) forms. Currently approved treatments consist of enzyme replacement therapy (ERT) and/or hematopoietic stem cell transplantation (HSCT). Patients with attenuated disease are often treated with ERT alone, while the recommended therapy for patients with Hurler syndrome consists of HSCT. While these treatments significantly improve disease manifestations and prolong life, a considerable burden of disease remains. Notably, treatment can partially prevent, but not significantly improve, clinical manifestations, necessitating early diagnosis of disease and commencement of treatment. This review discusses these standard therapies and their impact on common disease manifestations in patients with MPS I. Where relevant, results of animal models of MPS I will be included. Finally, we highlight alternative and emerging treatments for the most common disease manifestations.

Comparison of dermatan sulfate and heparan sulfate concentrations in serum, cerebrospinal fluid and urine in patients with mucopolysaccharidosis type I receiving intravenous and intrathecal enzyme replacement therapy

AIMS

To validate a liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the measurement of glycosaminoglycans (GAGs) in plasma and serum. To establish plasma, cerebrospinal fluid (CSF) and urine reference intervals. To compare GAGs in serum with that in urine and CSF from patients with MPS I.

METHODS

Dermatan sulfate (DS), heparan sulfate (HS), and chondroitin sulfate (CS) in serum/plasma, urine and CSF were methanolysed into dimers and analyzed using pseudo isotope dilution UPLC-MS/MS assay. Serum, CSF and urine DS and HS were quantified for 11 patients with mucopolysaccharidosis (MPS) type I before and after treatment with Aldurazyme® (laronidase) enzyme replacement therapy (ERT).

RESULTS

The method showed acceptable imprecision and recovery for the quantification of serum/plasma CS, DS, and HS. The serum, urine, and CSF DS and HS concentrations were reduced after 26 weeks of ERT in 4 previously untreated patients. Serum DS and HS concentrations normalized in some patients, and were mildly elevated in others after ERT. In contrast, urine and CSF DS and HS values remained elevated above the reference ranges. Compared with serum GAGs, urine and CSF DS and HS were more sensitive biomarkers for monitoring the ERT treatment of patients with MPS I.

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.

First Report of a Patient with MPS Type VII, Due to Novel Mutations in GUSB, Who Underwent Enzyme Replacement and Then Hematopoietic Stem Cell Transplantation

We report the case of a boy who was diagnosed with mucopolysaccharidosis (MPS) VII at two weeks of age. He harbored three missense β-glucuronidase (GUSB) variations in exon 3: two novel, c.422A>C and c.424C>T, inherited from his mother, and the rather common c.526C>T, inherited from his father. Expression of these variations in transfected HEK293T cells demonstrated that the double mutation c.422A>C;424C>T reduces β-glucuronidase enzyme activity. Enzyme replacement therapy (ERT), using UX003 (vestronidase alfa), was started at four months of age, followed by a hematopoietic stem cell allograft transplantation (HSCT) at 13 months of age. ERT was well tolerated and attenuated visceromegaly and skin infiltration. After a severe skin and gut graft-versus-host disease, ERT was stopped six months after HSCT. The last follow-up examination (at the age of four years) revealed a normal psychomotor development, stabilized growth curve, no hepatosplenomegaly, and no other organ involvement. Intriguingly, enzyme activity had normalized in leukocytes but remained low in plasma. This case report illustrates: (i) The need for an early diagnosis of MPS, and (ii) the possible benefit of a very early enzymatic and/or cellular therapy in this rare form of lysosomal storage disease.

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.

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.

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.

Cognitive and adaptive measurement endpoints for clinical trials in mucopolysaccharidoses types I, II, and III: A review of the literature

Sensitive, reliable measurement instruments are critical for the evaluation of disease progression and new treatments that affect the brain in the mucopolysaccharidoses (MPS). MPS I, II, and III have early onset clinical phenotypes that affect the brain during development and result in devastating cognitive decline and ultimately death without treatment. Comparisons of outcomes are hindered by diverse protocols and approaches to assessment including applicability to international trials necessary in rare diseases. We review both cognitive and adaptive measures with the goal of providing evidence to a Delphi panel to come to a consensus about recommendations for clinical trials for various age groups. The results of the consensus panel are reported in an accompanying article. The following data were gathered (from internet resources and from test manuals) for each measure and summarized in the discussion: reliability, validity, date and adequacy of normative data, applicability of the measure's metrics, cross cultural validity including translations and adaptations, feasibility in the MPS population, familiarity to sites, sensitivity to change, and interpretability. If, resulting from this consensus, standard protocols are used for both natural history and treatment studies, patients, their families, and health care providers will benefit from the ability to compare study outcomes.