Enzyme replacement therapy in juvenile glycogenosis type II: a longitudinal study

Comprehensive approach to weaning in difficult-to-wean infantile and juvenile-onset glycogen-storage disease type II patients: a case series

Background

Glycogen storage disease type II (GSD II) is caused by acid alpha-glucosidase (GAA) deficiency. Both infantile-onset and juvenile-onset GSD II lead to proximal muscle weakness and respiratory insufficiency and require mechanical ventilation. However, GSD II is also independently associated with delayed weaning from mechanical ventilation. This study aimed to describe a comprehensive approach including sequential invasive-noninvasive mechanical ventilation weaning and enzyme replacement therapy (ERT) in patients with weaning difficulties.

Case presentation

We studied six difficult-to-wean GSD II (three juvenile-onset, three infantile-onset) patients at the First Affiliated Hospital, Sun Yat-sen University from October 2015 to December 2017. Difficulty in weaning was defined as follows: the need for more than three spontaneous breathing trials or more than 1 week to achieve successful weaning. All patients received comprehensive treatment including sequential invasive-noninvasive mechanical ventilation weaning, ERT and general treatment. Recombinant human acid alpha-glucosidase enzyme therapy (20 mg/kg every 14 days) was used after diagnosis, and Patients 1–6 received ERT for 15.5, 4.5, 2, 2.5, 17, and 2 months, respectively. The therapeutic effect of the comprehensive treatment was observed.

The patients’ respiratory function and limb muscle strength improved after each ERT session. Patients who successfully completed a spontaneous breathing trial could proceed to extubation, and then start non-invasive ventilation. The patients’ age range at initial mechanical ventilation was 3–47 (median 26.5) months, duration of invasive ventilation was 1–36 (median 2.75) months, and duration of noninvasive ventilation was 0–0.6 (median 0.05) month. The patients’ nutritional status improved after enhanced nutritional support. Patients 2, 3, and 5 were successfully weaned off the ventilator. Patient 1 underwent tracheal intubation after six weaning failures, and Patients 4 and 6 died after therapy was abandoned by their parents.

Discussion and conclusions

Male sex, GSD II type, and the presence of malnutrition and neurological impairment may predict poor respiratory outcomes. The above-described comprehensive sequential invasive-noninvasive mechanical ventilation weaning strategy may increase the success rate of weaning from mechanical ventilation.

Forced vital capacity and cross-domain late-onset Pompe disease outcomes: an individual patient-level data meta-analysis

Background

Late-onset Pompe disease (LOPD) is a rare, metabolic disease primarily affecting the musculoskeletal and respiratory systems. Forced vital capacity (FVC) is commonly used to measure pulmonary function; however, associations between FVC and other LOPD outcomes remain unclear.

Methods

A systematic literature review was conducted on November 2015, updated September 2016 and supplemented with clinical trial data from the sponsor. Outcomes included: 6-min walk test distance (6MWT), FVC, maximal inspiratory/expiratory pressure (MIP/MEP), Medical Research Council-skeletal muscle strength score (MRC), 36-item short-form survey-physical component score (SF-36), Rotterdam Handicap Scale (RHS), Fatigue Severity Scale (FSS) and survival. Individual patient data meta-analysis was used for cross-sectional analyses and longitudinal analyses to determine associations between percent of predicted FVC and LOPD measures and outcomes.

Results

Fifteen studies were selected. From cross-sectional analyses, FVC and MRC were most strongly associated. Specifically, patients with 10% higher FVC (a round number for illustrative purposes only) were associated with a 4.72% (95% confidence interval [CI]: 3.37, 6.07) higher MRC score, indicating a positive association. Similarly, slopes for the 6MWT and SF-36 relative to a 10% higher FVC were estimated at 33.2 meters (95% CI 24.0, 42.4) and 1.2% (95% CI 0.24, 2.16%), respectively. From longitudinal analyses, a 10% incremental increase in predicted FVC was associated with an average increase of 4.12% in MRC score (95% CI 1.29, 6.95), 35.6 m in the 6MWT (95% CI 19.9, 51.6), and 1.34% in SF-36 (95% CI 0.08, 2.60). There was insufficient data to conduct analyses for RHS, FSS and survival.

Conclusions

FVC is positively associated with LOPD measures and outcomes across multiple domains. Additionally, longitudinal changes in FVC are positively associated with changes in the 6MWT, MRC and SF-36.

Electronic supplementary material

The online version of this article (10.1007/s00415-019-09401-1) contains supplementary material, which is available to authorized users.

Early-onset of symptoms and clinical course of Pompe disease associated with the c.-32-13 T > G variant

BACKGROUND

Individuals with late-onset Pompe disease (LOPD) and the common c.-32-13 T > G variant are widely thought to have milder, adult-onset disease. This belief, and the consequent low suspicion of clinical involvement in children, has led to delays in diagnosis and treatment initiation in patients with early onset of symptoms. Previous reports of LOPD in children do not include description of the early-onset phenotype. This description of signs and symptoms, some of which are subtle and less known, is important to facilitate prompt identification and appropriate treatment in symptomatic children.

METHODS

Retrospective chart review of a cohort of 84 LOPD patients with the c.-32-13 T > G variant was conducted to identify patients diagnosed clinically (as opposed to through newborn screening) who had clinically documented symptom-onset within the first two years of life.

RESULTS

Four patients had early onset of symptoms, with age at onset ranging from 10 days to 20 months. Initial symptoms included delay in achievement of gross motor milestones, signs of proximal muscle weakness, swallow and feeding difficulties, and sleep apnea. Early and characteristic alterations in posture and movement were identified in all patients. Age at diagnosis ranged from 10 months to 26 months. Median age at enzyme replacement therapy (ERT) initiation was 23.5 months. Despite ERT, progression of musculoskeletal involvement and residual muscle weakness was evident in all patients, as evidenced by ptosis, myopathic facies, scoliosis, lumbar lordosis, scapular winging, and trunk and lower extremity weakness. Standardized functional assessments showed gross motor function below age level as measured by the Alberta Infant Motor Scales, the Peabody Developmental Motor Scales-2, the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition, and the six-minute walk test.

CONCLUSIONS

Onset of symptoms including delay in achievement of gross motor milestones, signs of proximal muscle weakness, swallow and feeding difficulties, and sleep apnea in the first two years of life is not uncommon in individuals with LOPD and the c.-32-13 T > G variant. Patients with early-onset disease appear to have a more, rapid and severe progression of disease with persistent residual muscle deficits which partially improve with higher doses of ERT. Careful evaluation for specific and characteristic patterns of posture and movement in patients with this variant is necessary to identify those who have early onset of disease. Increased awareness of the early-onset signs and symptoms may also enable early identification of disease onset in children who are diagnosed through newborn screening.

The effectiveness of enzyme replacement therapy for juvenile-onset Pompe disease: A systematic review

AIM

The objective of this research was to determine the effectiveness of enzyme replacement therapy for juvenile-onset Pompe disease (patients aged 2 to 18 years at symptom onset) by systematic review.

METHODS

A systematic search was conducted according to a protocol designed a priori of bibliographic databases and search engines. Studies selected according to pre-specified criteria were assessed for quality and risk of bias using standardised appraisal tools. Data were reported according to PRISMA conventions (Liberati et al. in PLoS Med 6:e1000100, 2009) and synthesised using GRADE (Guyatt et al. in J Clin Epidemiol 64:380-382, 2011).

RESULTS

Of 2537 titles screened, 1 case series and 16 case reports met the inclusion criteria. No studies reported on the impact of enzyme replacement therapy on the survival of juvenile-onset patients. Low level evidence found that respiratory function may improve or be maintained in the early months of therapy. Improved muscle function in the first 6 to 12 months was also suggested, but results may be confounded by natural development. Patients with less severe baseline status and treated at a younger age showed more response than patients with more severe baseline status, treated as adults.

CONCLUSIONS

Interpretation of the findings was hindered by the lack of good quality evidence. The available data suggests that some JOPD patients may benefit in the short term from ERT through improved muscle strength and a reduced need for assisted ventilation. A focus by clinicians on improved and more consistent evidence collection, and use of study designs tailored to rare conditions, would provide more definitive results.

Long-term follow-up of 17 patients with childhood Pompe disease treated with enzyme replacement therapy

OBJECTIVES

Pompe disease is a progressive metabolic myopathy for which enzyme replacement therapy (ERT) was approved in 2006. While various publications have examined the effects of ERT in classic-infantile patients and in adults, little has been published on ERT in children with non-classic presentations.

STUDY DESIGN

This prospective study was conducted from June 1999 to May 2015. Seventeen patients from various countries participated. Outcome measures comprised muscle function (6-minute walk test, quick motor-function test (QMFT)), muscle strength (hand-held dynamometry; manual muscle testing), and lung function (FVC sitting and supine). For each outcome measure, we used linear mixed-effects models to calculate the difference at group level between the start of therapy and 7 years of ERT. Patients' individual responses over time were also evaluated.

RESULTS

Eleven males and six females started ERT at ages between 1.1 and 16.4 years (median 11.9 years); 82% of them carried the common c.-32-13T > G GAA gene variant on one allele. At group level, distance walked increased by 7.4 percentage points (p < 0.001) and QMFT scores increased by 9.2 percentage points (p = 0.006). Muscle strength scores seemed to remain stable. Results on lung function were more variable. Patients' individual data show that the proportion of patients who stabilized or improved during treatment ranged between 56 and 69% for lung function outcomes and between 71 and 93% for muscle strength and muscle function outcomes.

CONCLUSIONS

We report a positive effect of ERT in patients with childhood Pompe disease at group level. For some patients, new or personalized treatments should be considered.

Elevated Creatine Kinase in a 6-Year-Old Boy

Paucisymptomatic or asymptomatic but persistently elevated serum creatine kinase is not an uncommon pediatric neurology referral question. The challenge is in promptly identifying etiologies with specific treatments, even if they are rare. The presenting features for a child or adolescent with juvenile-onset Pompe disease (JOPD) can be nonspecific and heterogeneous. Clinical manifestations can appear at any age after 2 years and before adulthood, with insidious onset of symptoms related to slowly progressive skeletal or respiratory muscle weakness. This reported case highlights the importance of screening for JOPD in children with "hyper-CK-emia." Dried blood spot measuring acid α-glucosidase enzyme activity is reliable, rapid, noninvasive, and inexpensive, allowing early diagnosis. Diagnosis of JOPD is important as enzyme replacement therapy with alglucosidase alpha, an intravenous recombinant α-glucosidase, is available, and early treatment improves muscle function, quality of life, and long-term survival.

Insight into the phenotype of infants with Pompe disease identified by newborn screening with the common c.-32-13T>G "late-onset" GAA variant

OBJECTIVE

Newborn screening (NBS) has led to early diagnosis and early initiation of treatment for infantile onset Pompe Disease (IOPD). However, guidelines for management of late onset Pompe disease (LOPD) via NBS, especially with the IVS c.-32-13T>G are not clear. This IVS variant is noted in 68-90% cases with LOPD and has been presumed to result in "adult" disease in compound heterozygosity, with a few cases with earlier onset and a mild to no phenotype in homozygosity. Our study evaluates newborns with LOPD having IVS variant with a diligent multidisciplinary approach to determine if they have an early presentation.

METHODS

Seven children with LOPD identified by NBS with IVS variant (3 compound heterozygous, and 4 homozygous) were evaluated with clinical, biochemical (CK, AST, ALT, and urinary Glc₄), cardiac evaluation, physical therapy (PT), occupational, and speech/language therapy.

RESULTS

All seven patients demonstrated motor involvement by age 6months; the three patients with c.-32-13 T>G variant in compound heterozygosity had symptoms as neonates. Patients with c.-32-13 T>G variant in compound heterozygosity had more involvement with persistent hyperCKemia, elevated AST and ALT, swallowing difficulties, limb-girdle weakness, delayed motor milestones, and were initiated on ERT. The patients with c.-32-13T>G variant in homozygosity had normal laboratory parameters, and presented with very subtle yet LOPD specific signs, identified only by meticulous assessments.

CONCLUSION

This patient cohort represents the first carefully phenotyped cohort of infants with LOPD with the "late-onset" GAA variant c.-32-13T>G detected by NBS in the USA. It emphasizes not only the opportunity for early detection of skeletal and other muscle involvement in infants with c.-32-13T>G variant but also a high probability of overlooking or underestimating the significance of clinically present and detectable features. It can thus serve as a valuable contribution in the development of evaluation and treatment algorithms for infants with LOPD.

Investigation on acute effects of enzyme replacement therapy and influence of clinical severity on physiological variables related to exercise tolerance in patients with late onset Pompe disease

Exercise intolerance is one of the clinical hallmarks of late-onset Pompe disease (LOPD). We studied the acute effects of ERT on the physiological variables associated with exercise tolerance in patients chronically ERT treated. Moreover, we assessed the influence of clinical severity on the investigated variables. The day before (B) and the day after (A) ERT injection, 11 LOPD patients performed on a cycle-ergometer an exercise tolerance test to voluntary exhaustion; VO₂, HR, RPE, and GAA activity were determined in B and A. The disease severity was characterized by Walton scale, 6MWT, and pulmonary function tests. No significant differences in the variables related to exercise tolerance were found in A vs B, despite a significant increase in GAA activity in peripheral lymphocytes. No differences in VO₂ peak were observed between patients with only skeletal muscle impairment and patients with both skeletal and respiratory muscle impairment. Distance walked at 6MWT was significantly higher than VO₂ peak expressed as percentage of normal values. In conclusion, in LOPD patients the exercise tolerance test is not acutely affected by ERT administration; the peripheral muscle component seems more prominent in determining the VO₂ peak decrease than the respiratory component; VO₂ peak might be more sensitive than 6MWT in estimating exercise tolerance in LOPD.

Autophagy in Natural History and After ERT in Glycogenosis Type II

We studied the role of autophagy in a series of 10 infantile-, juvenile-, and adult-onset GSDII patients and investigated autophagy blockade in successive biopsies of adult cases during disease natural history. We also correlated the autophagosome accumulation and efficiency of enzyme replacement therapy (ERT) in four treated cases (two infantile and two juvenile-adult onsets).The autophagic flux was monitored by measuring the amount of p62-positive protein aggregates and compared, together with fibre vacuolisation, to fibre atrophy.A blocked autophagic flux resulted in p62 accumulation, increased vacuolisation, and progressive atrophy of muscle fibres in biopsies collected from patients during natural history. On the contrary, in the GSDII cases early treated with ERT, the autophagic flux improved and muscle fibre atrophy, fibre vacuolisation, and acid phosphatase activity decreased.The functionality of the autophagy-lysosome system is essential in GSDII muscle, which is characterised by the presence of swollen glycogen-filled lysosomes and autophagic build-up. Defining the role of autophagy and its relationship with muscle loss is critical for understanding the disease pathogenesis, for developing new therapies, and for improving ERT efficacy in GSDII.