[Diagnosis and Management of Late-Onset Pompe Disease]

Pompe disease is a lysosomal storage disorder, with onset between the first weeks after birth and adulthood, depending on its phenotype. It can affect multiple organ systems and presents itself with a wide variety of symptoms. Thus, recognizing Pompe disease is difficult. Especially since enzyme replacement therapy for Pompe disease was introduced (in Germany in 2006), early diagnosis by means of enzyme activity determination from dried blood spot analysis and genetic verification has become important for outcome and quality of life. When facing an obscure muscular disorder, it is crucial to consider Pompe disease. This article provides an overview about Pompe disease and focuses on the diagnosis of the late onset type. The most important aspects of interdiciplinary care for patients with Pompe disease are presented. Additionally, it contains a section focusing on psychosocial challenges for children with Pompe disease and their families, which may include mental disorders and social retreat, and gives advice on how to support parents of affected children.

Gut dysmotility in children with neurological impairment: the nutritional management

Intestinal motility disorders represent a frequent problem in children with neurological impairment. These conditions are characterized by abnormal movements of the gut, which can result in symptoms such as constipation, diarrhea, reflux, and vomiting. The underlying mechanisms leading to dysmotility are various, and the clinical manifestations are often nonspecific. Nutritional management is an important aspect of care for children with gut dysmotility, as it can help to improve their quality of life. Oral feeding, when safe and in the absence of risk of ingestion or severe dysphagia, should always be encouraged. When oral nutrition is insufficient or potentially harmful, it is necessary to switch to an enteral by tube or parenteral nutrition before the onset of malnutrition. In most cases, children with severe gut dysmotility may require feeding via a permanent gastrostomy tube to ensure adequate nutrition and hydration. Drugs may be necessary to help manage gut dysmotility, such as laxatives, anticholinergics and prokinetic agents. Nutritional management of patients with neurological impairment often requires an individualized care plan to optimize growth and nutrition and to improve overall health outcomes. This review tries to sum up most significant neurogenetic and neurometabolic disorders associated with gut dysmotility that may require a specific multidisciplinary care, identifying a proposal of nutritional and medical management.

Prevalence of lower urinary tract symptoms in children with early-treated infantile-onset Pompe disease: A single-centre cross-sectional study

AIM

To evaluate lower urinary tract symptoms (LUTS) in children with infantile-onset Pompe disease (IOPD) who received early treatment.

METHODS

Pompe disease (PD), or glycogen storage disease II is a rare autosomal recessive lysosomal storage disease that affects multiple organ systems. To our knowledge, only one study has focused on the relationship between LUTS and incontinence in children with PD. This cross-sectional study was conducted from August 2019 through March 2021 and children with IOPD, who had received early and regular enzyme replacement therapy, were enrolled. Participants or their parents completed the Dysfunctional Voiding Scoring System (DVSS) questionnaire. All children underwent uroflowmetry and postvoid residual urine measurements. Fourteen children (age, 4-9 years) with IOPD were enrolled.

RESULTS

Ten patients (71.4%) had abnormal uroflow curves. In addition, results of the DVSS revealed that approximately half (42.9%) of our IOPD patients had voiding dysfunction, with urinary incontinence as the most common symptom (64.3%, 9/14). No significant correlations were found between LUTS and uroflow curves in children with IOPD.

CONCLUSIONS

The frequency of LUTS and lower urinary tract dysfunction noted on uroflowmetry should encourage pediatricians to actively identify IOPD patients with LUTS, regardless of the timing and frequency of their treatments, and refer them to a urologist for further evaluation and appropriate treatment.

New Insights into Gastrointestinal Involvement in Late-Onset Pompe Disease: Lessons Learned from Bench and Bedside

BACKGROUND

There are new emerging phenotypes in Pompe disease, and studies on smooth muscle pathology are limited. Gastrointestinal (GI) manifestations are poorly understood and underreported in Pompe disease.

METHODS

To understand the extent and the effects of enzyme replacement therapy (ERT; alglucosidase alfa) in Pompe disease, we studied the histopathology (entire GI tract) in Pompe mice (GAAKO 6^neo/6^neo). To determine the disease burden in patients with late-onset Pompe disease (LOPD), we used Patient-Reported Outcomes Measurements Information System (PROMIS)-GI symptom scales and a GI-focused medical history.

RESULTS

Pompe mice showed early, extensive, and progressive glycogen accumulation throughout the GI tract. Long-term ERT (6 months) was more effective to clear the glycogen accumulation than short-term ERT (5 weeks). GI manifestations were highly prevalent and severe, presented early in life, and were not fully amenable to ERT in patients with LOPD (n = 58; age range: 18-79 years, median age: 51.55 years; 35 females; 53 on ERT).

CONCLUSION

GI manifestations cause a significant disease burden on adults with LOPD, and should be evaluated during routine clinical visits, using quantitative tools (PROMIS-GI measures). The study also highlights the need for next generation therapies for Pompe disease that target the smooth muscles.

Nutrition in adult patients with selected lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a group of clinically heterogeneous disorders affecting the function of lysosomes and are characterized by an accumulation of undigested substrates within several cell types. In recent years there have been substantial advances in supportive care and drug treatment for some LSDs, leading to improved patient survival, as seen in Gaucher, Pompe and Fabry disease and some Mucopolysaccharidoses; however, many symptoms still persist. Thus it is now even more important to improve patients' quality of life and reduce symptoms and comorbidities. One potential way of achieving this goal is through adjunct nutritional therapy, which is challenging as patients may be overweight with associated consequences, or malnourished, or underweight. Furthermore, drugs used to treat LSDs can modify the metabolic status and needs of patients. There are currently not enough data to make specific dietary recommendations for individual LSDs; however, suggestions can be made for managing clinical manifestations of the diseases, as well as treatment-associated adverse events. The metabolic and nutritional status of adult patients must be regularly assessed and individualized dietary plans may be created to cater to a patient's specific needs. Damage to the autophagic process is a common feature in LSDs that is potentially sensitive to dietary manipulation and needs to be assessed in clinical studies.

Glycogen accumulation in smooth muscle of a Pompe disease mouse model

Pompe disease is a lysosomal storage disease caused by mutations within the GAA gene, which encodes acid α-glucosidase (GAA)—an enzyme necessary for lysosomal glycogen degradation. A lack of GAA results in an accumulation of glycogen in cardiac and skeletal muscle, as well as in motor neurons. The only FDA approved treatment for Pompe disease—an enzyme replacement therapy (ERT)—increases survival of patients, but has unmasked previously unrecognized clinical manifestations of Pompe disease. These clinical signs and symptoms include tracheo-bronchomalacia, vascular aneurysms, and gastro-intestinal discomfort. Together, these previously unrecognized pathologies indicate that GAA-deficiency impacts smooth muscle in addition to skeletal and cardiac muscle. Thus, we sought to characterize smooth muscle pathology in the airway, vascular, gastrointestinal, and genitourinary in the Gaa^−/− mouse model. Increased levels of glycogen were present in smooth muscle cells of the aorta, trachea, esophagus, stomach, and bladder of Gaa^−/− mice, compared to wild type mice. In addition, there was an increased abundance of both lysosome membrane protein (LAMP1) and autophagosome membrane protein (LC3) indicating vacuolar accumulation in several tissues. Taken together, we show that GAA deficiency results in subsequent pathology in smooth muscle cells, which may lead to life-threatening complications if not properly treated.

Intracranial aneurysm management in patients with late-onset Pompe disease (LOPD)

Pompe disease is a rare hereditary metabolic disorder caused by α-glucosidase (GAA) deficiency. The late-onset form of the disease (LOPD) is considered a multisystemic disorder which could involve vascular system with cerebrovascular abnormalities such as intracranial aneurysms or dolichoectasia. Intracranial aneurysm rupture may represent a life-threatening emergency. A possible treatment of unruptured intracranial aneurysms (UIAs) should consider both aneurysm-related (aneurysmal size, shape, localization, numbers and hemodynamic factors) and patient-related risk factors (patient's age and sex, hypertension, smoke exposure). Moreover, UIAs management of LOPD patients needs also to take into account the altered blood vessels integrity and elasticity, whose consistency is likely weakened by the deficient GAA activity as a further potential risk factor. We herein present our approach for of UIAs management in three patients with LOPD. Among them, only one patient with a left saccular UIA of the anterior communicating artery, after careful consideration of risk factors, underwent the endovascular treatment. The other two patients were scheduled for a 1-year follow-up, according to radiological, clinical, and risk evaluation features. Finally, we would like to suggest some general recommendations for UIAs management. In particular, if no risk factors are identified, a cautious yearly follow-up is suggested; otherwise, if risk factors are present, endovascular treatment should be considered.

Urodynamic and clinical studies in patients with late-onset Pompe disease and lower urinary tract symptoms

AIMS

In late-onset Pompe disease (LOPD), a lysosomal storage disorder with glycogen accumulation in several tissues, patients suffer from progressive skeletal muscle weakness. Lower urinary tract symptoms (LUTS) have rarely been reported. The aim of this study is to objectively assess LUTS in patients with LOPD for the first time using urodynamic studies and to determine differences between LOPD patients with and without LUTS.

METHODS

Eighteen patients with LOPD were recruited, of whom seven patients (38.9%) reported LUTS (both voiding and storage symptoms). Six of these patients underwent urodynamic studies. Medical histories and motor function tests were compared between the 7 patients with LUTS and the 11 patients without LUTS. The Student t test was used to determine an association between the two cohorts.

RESULTS

In the seven LOPD patients with LUTS urodynamics revealed neurogenic dysfunction, underactive detrusor, and bladder outlet obstruction. These patients had suffered from clinical symptoms for a longer period of time before starting enzyme replacement therapy (P = .017) than patients without LUTS. They also scored more poorly on muscle function tests. Urodynamic results point to neurogenic causes for LUTS in LOPD, that is, neurogenic reflex bladder or impaired filling sensation. This could be due to glycogen accumulation in the urothelium and central nervous system. Patients with LUTS also seem to be more severely affected by LOPD than patients without LUTS.

CONCLUSION

LUTS in LOPD requires early and specific treatment to limit the development of severe health problems. Urodynamic studies should be considered in assessing LUTS.

Late-onset Pompe disease (LOPD) in Belgium: clinical characteristics and outcome measures

Background

Late-onset Pompe disease (LOPD) is a rare, hereditary, progressive disorder that is usually characterized by limb-girdle muscle weakness and/or respiratory insufficiency. LOPD is caused by mutations in the acid alpha-glucosidase (GAA) gene and treated with enzyme replacement therapy (ERT).

Methods

We studied the clinical, brain imaging, and genetic features of the Belgian cohort of late-onset Pompe disease patients (N = 52), and explored the sensitivity of different outcome measures, during a longitudinal period of 7 years (2010–2017), including the activity limitations ActivLim score, 6 min walking distance (6MWD), 10 m walk test (10MWT), MRC sum score, and forced vital capacity (FVC) sitting/supine.

Results

In Belgium, we calculated an LOPD prevalence of 3.9 per million. Mean age at onset of 52 LOPD patients was 28.9 years (SD: 15.8 y), ranging from 7 months to 68 years. Seventy-five percent (N = 39) of the patients initially presented with limb-girdle weakness, whereas in 13% (N = 7) respiratory symptoms were the only initial symptom. Non-invasive ventilation (NIV) was started in 37% (N = 19), at a mean age of 49.5 years (SD: 11.9 y), with a mean duration of 15 years (SD: 10.2 y) after symptom onset. Brain imaging revealed abnormalities in 25% (N = 8) of the patients, with the presence of small cerebral aneurysm(s) in two patients and a vertebrobasilar dolichoectasia in another two. Mean diagnostic delay was 12.9 years. All patients were compound heterozygotes with the most prevalent mutation being c.-32-13 T > G in 96%. We identified two novel mutations in GAA: c.1610_1611delA and c.186dup11. For the 6MWD, MRC sum score, FVC sitting and FVC supine, we measured a significant decrease over time (p = 0.0002, p = 0.0001, p = 0.0077, p = 0.0151), which was not revealed with the ActivLim score and 10MWT (p > 0.05).

Conclusions

Awareness on LOPD should even be further increased because of the long diagnostic delay. The 6MWD, but not the ActivLim score, is a sensitive outcome measure to follow up LOPD patients.

Multisystem late onset Pompe disease (LOPD): an update on clinical aspects

Pompe disease is classified by age of onset, organ involvement, severity, and rate of progression in two main forms: the first one, infantile onset Pompe disease (IOPD), presents before the age of 12 months with generalized muscle weakness, hypotonia, respiratory distress, and hypertrophic cardiomyopathy as main clinical features. The second form, late onset Pompe disease (LOPD), is characterized by an onset at the age of 12 months to adulthood, hyperCKemia, and limb-girdle and axial muscle weakness, often complicated by respiratory muscles degeneration. In the last 10-15 years, an increasing interest in Pompe disease has led to multiple studies in an effort to clarify the emerging clinical aspects, to find out the best diagnostic tools to identify the disease as early as possible, and to offer new therapeutic options apart from enzyme replacement therapy (ERT). Since 2006, ERT-the first treatment for Pompe disease-has been universally accepted in the majority of countries all over the world. Although for years Pompe disease has been primarily considered a muscle disorder, nowadays it is clear that the involvement of several other organs has changed the cultural approach to this entity which is now viewed as a multisystem disorder. The emerging clinical aspects have greatly expanded the spectrum of the disease manifestations. In fact, central, peripheral, and autonomous nervous systems are often involved; vascular malformations and heart involvement are frequently observed; musculoskeletal and bone changes as well as oro-gastrointestinal and urinary tract alterations have been better defined. A great deal of effort has been made to clarify the clinical aspects of Pompe disease, to raise awareness of the LOPD patients' problems and to improve their quality of life.

The impact of Pompe disease on smooth muscle: a review

Pompe disease (OMIM 232300) is an autosomal recessive disorder caused by mutations in the gene encoding acid α-glucosidase (GAA) (EC 3.2.1.20), the enzyme responsible for hydrolyzing lysosomal glycogen. The primary cellular pathology is lysosomal glycogen accumulation in cardiac muscle, skeletal muscle, and motor neurons, which ultimately results in cardiorespiratory failure. However, the severity of pathology and its impact on clinical outcomes are poorly described in smooth muscle. The advent of enzyme replacement therapy (ERT) in 2006 has improved clinical outcomes in infantile-onset Pompe disease patients. Although ERT increases patient life expectancy and ventilator free survival, it is not entirely curative. Persistent motor neuron pathology and weakness of respiratory muscles, including airway smooth muscles, contribute to the need for mechanical ventilation by some patients on ERT. Some patients on ERT continue to experience life-threatening pathology to vascular smooth muscle, such as aneurysms or dissections within the aorta and cerebral arteries. Better characterization of the disease impact on smooth muscle will inform treatment development and help anticipate later complications. This review summarizes the published knowledge of smooth muscle pathology associated with Pompe disease in animal models and in patients.

The emerging phenotype of late-onset Pompe disease: A systematic literature review

BACKGROUND

Pompe disease is an autosomal recessive disorder caused by deficiency of the lysosomal glycogen-hydrolyzing enzyme acid α-glucosidase (GAA). The adult-onset form, late-onset Pompe disease (LOPD), has been characterized by glycogen accumulation primarily in skeletal, cardiac, and smooth muscles, causing weakness of the proximal limb girdle and respiratory muscles. However, increased scientific study of LOPD continues to enhance understanding of an evolving phenotype.

PURPOSE

To expand our understanding of the evolving phenotype of LOPD since the approval of enzyme replacement therapy (ERT) with alglucosidase alfa (Myozyme™/Lumizyme™) in 2006.

METHODS

All articles were included in the review that provided data on the charactertistics of LOPD identified via the PubMed database published since the approval of ERT in 2006. All signs and symptoms of the disease that were reported in the literature were identified and included in the review.

RESULTS

We provide a comprehensive review of the evolving phenotype of LOPD. Our findings support and extend the knowledge of the multisystemic nature of the disease.

CONCLUSIONS

With the advent of ERT and the concurrent increase in the scientific study of LOPD, the condition once primarily conceptualized as a limb-girdle muscle disease with prominent respiratory involvement is increasingly recognized to be a condition that results in signs and symptoms across body systems and structures.

Intracranial arterial abnormalities in patients with late onset Pompe disease (LOPD)

BACKGROUND AND OBJECTIVES

Pompe disease is a rare metabolic disorder due to lysosomal alpha-glucosidase (GAA) deficiency. It is considered as a multi-systemic disease since, although glycogen accumulation is largely prominent in heart, skeletal and respiratory muscles, other organs can also be affected. As regards the vascular system, few reports have documented cerebrovascular malformations in Pompe patients. The aim of this study was to define the presence and type of intracranial arterial abnormalities in a cohort of late onset Pompe disease (LOPD) patients.

METHODS

We have studied 21 LOPD patients with cerebral CT angiography (CTA), using maximum intensity projection and volume rendering technique for 3D-image reconstruction.

RESULTS

We found intracranial arterial abnormalities in 13/21 patients (62 %), of whom: 2/21 patients (9.5 %) showed an unruptured intracranial aneurysm (respectively 2 and 4 mm), 10/21 (47 %) had a vertebrobasilar dolichoectasia (VBD) and 1/21 a basilar artery fenestration. Signs of lacunar encephalopathy (insular, capsular and frontal subcortical lesions) were detected in 13/21 patients (62 %) and this correlated with the presence of respiratory impairment (p = 0.017).

CONCLUSIONS

These findings differ from what has been previously observed in healthy, aged-matched populations and confirm that cerebral arteries abnormalities, mainly involving the posterior circle, are not so rare in LOPD patients and are often accompanied by a lacunar encephalopathy that might represent a hypoxic-ischemic origin. A CTA or an MRA is recommended, in LOPD patients, for early detection of cerebrovascular malformations as they could lead to life-threatening events such as sub-arachnoid haemorrhage or brainstem compression.

Postmortem Findings and Clinical Correlates in Individuals with Infantile-Onset Pompe Disease

Pompe disease (OMIM 232300), a glycogen storage disorder caused by deficiency in the lysosomal enzyme acid alpha-glucosidase (EC 3.2.1.20), results in weakness and cardiomyopathy in infants affected with the classic form. Although the primary disease manifestations are due to glycogen accumulation in skeletal and cardiac muscle, glycogen also accumulates in a variety of additional tissues. To improve our understanding of disease pathogenesis in long-term survivors, we reviewed postmortem results for three infants with the classic form of Pompe disease. We have observed a number of new complications in long-term survivors of infantile-onset Pompe disease, and we focused this postmortem study on pathological correlates. Findings in survivors include cardiac arrhythmias, which may be related to glycogen accumulation in cardiac conduction tissue; urinary incontinence, likely due to glycogen accumulation in smooth muscle; and refractory errors, possibly related to accumulation in ocular structures. These observations provide potential pathophysiologic correlates for complications in long-term survivors of infantile Pompe disease.

Expanding our understanding of lower urinary tract symptoms and incontinence in adults with pompe disease

OBJECTIVE

To study the prevalence of lower urinary tract symptoms (LUTS) and incontinence in late-onset Pompe disease (LOPD) Methods: Adult LOPD patients seen at the Duke Pompe Clinic were prospectively recruited and asked to complete validated questionnaires on LUTS and incontinence as part of an IRB-approved study. Patient demographics as well as previous urologic history were reviewed.

RESULTS

35 patients with LOPD were included in the study (17 males and 18 females). The median age was 51.8 (range 18-72 years of age). Of these patients, 27/35 were receiving enzyme replacement therapy (ERT) with median duration of 54 months (range 5-88 months). In the male patients, 9/17 (53%) described their stream as dribbling, weak, or intermittent, and 9/17 (53%) complained of post-void dribbling. In addition 38% of the men were unable to stop their urination midstream. In the female patients, the most common complaint was urinary incontinence, reported in 14/18 (78%). In addition, 7/18 (39%) complained of post-void dribbling, and 47% were unable to stop their urination midstream. Bowel incontinence was reported in 45% of patients. There was a significant association between urinary symptoms and lower extremity function scores and duration of ERT (p = 0.005 and p = 0.04, respectively)

CONCLUSIONS

This is the first study in a large cohort of LOPD patients that demonstrates LUTS and incontinence occur at a high rate. This study emphasizes the spectrum of LOPD is beyond isolated gross motor and pulmonary involvement and has a significant effect on the lower urinary tract.

Urge incontinence and gastrointestinal symptoms in adult patients with pompe disease: a cross-sectional survey

OBJECTIVE

To determine the frequency and impact of gastrointestinal symptoms, and bowel and urinary incontinence, as this is currently unknown in adults with Pompe disease.

METHODS

Adult German Pompe patients and age- and gender-matched controls were asked about symptoms in the upper and lower intestinal tract as well as urinary incontinence using the Gastrointestinal Symptoms Questionnaire and the International Consultation on Incontinence Questionnaires for Bowel Symptoms and Urinary Incontinence.

RESULTS

The overall response rate was 78%; 57 patients and 57 controls participated. The mean age of the patients was 48.3 years ±14.7 (28 female, 29 male). 84% of patients were receiving enzyme replacement therapy. Stool urgency, diarrhoea, and urinary urge incontinence were reported significantly more frequently in patients compared to the age- and gender-matched controls (55%, 56%, 33% vs. 20%, 18%, 7%). 20% of Pompe patients used loperamide daily against diarrhoea. No other gastrointestinal tract-related symptoms were reported to occur more frequently in Pompe patients than in controls.

CONCLUSIONS

Compared to age- and gender-matched controls, both urinary and bowel incontinence occur in a higher frequency in adults with Pompe disease and have a major impact on daily life.

New insights in the field of muscle glycogenoses

PURPOSE OF REVIEW

This review highlights recent contributions regarding clinical heterogeneity, pathogenic mechanisms, therapeutic trials, and animal models of the muscle glycogenoses.

RECENT FINDINGS

Most recent publications have dealt with the clinical effects of enzyme replacement therapy (ERT) in glycogenosis type II (Pompe disease), including the cognitive development of children with the infantile form who have reached school age. Standardized exercise testing has shown the similarity between McArdle disease and one of the most recently described muscle glycogenoses, phosphoglucomutase deficiency. Cycle ergometry in patients with glycogenosis type III (debrancher deficiency) without overt weakness has documented exercise intolerance relieved by glucose infusion, consistent with the glycogenolytic block. A mouse model of McArdle disease faithfully recapitulates most features of the human disease and will prove valuable for a better understanding of pathogenesis and therapeutic modalities. Polyglucosan body myopathy with cardiomyopathy has been associated with mutations in RBCK1, a ubiquitin ligase, which have also been reported in children with early-onset immune disorder. The role of polyglucosan storage in muscle and in both central and peripheral nervous systems has been confirmed in the infantile and late-onset forms of glycogenosis type IV (brancher enzyme deficiency). Additional novel findings include the involvement of the heart in one patient with phosphofructokinase (PFK) deficiency and the presence of tubular aggregates in a manifesting heterozygote with phosphoglycerate mutase deficiency.

SUMMARY

Important recent developments in the field of muscle glycogenoses include a new disease entity, a new animal model of McArdle disease, and better knowledge of the pathogenesis in some glycogenoses and of the long-term effects of enzyme replacement therapy in Pompe disease.

Anaesthetic management of two patients with pompe disease for caesarean section

The introduction of enzyme replacement therapy and the resultant stabilisation or improvement in mobility and respiratory muscle function afforded to patients with late-onset Pompe may lead to an increased number of Pompe patients prepared to accept the challenges of parenthood. In this case report, we describe our anaesthetic management of two patients with Pompe disease for a caesarean section.

Extended phenotype description and new molecular findings in late onset glycogen storage disease type II: a northern Italy population study and review of the literature

Glycogen storage disease type II (GSDII) is a lysosomal storage disorder caused by acid alpha-1,4-glucosidase deficiency and associated with recessive mutations in its coding gene GAA. Few studies have provided so far a detailed phenotypical characterization in late onset GSDII (LO-GSDII) patients. Genotype-phenotype correlation has been previously attempted with controversial results. We aim to provide an in-depth description of a cohort (n = 36) of LO-GSDII patients coming from the north of Italy and compare our population's findings to the literature. We performed a clinical record-based retrospective and prospective study of our patients. LO-GSDII in our cohort covers a large variability of phenotype including subtle clinical presentation and did not differ significantly from previous data. In all patients, molecular analysis disclosed GAA mutations, five of them being novel. To assess potential genotype-phenotype correlations we divided IVS1-32-13T>G heterozygous patients into two groups following the severity of the mutations on the second allele. Our patients harbouring "severe" mutations (n = 21) presented a strong tendency to have more severe phenotypes and more disability, more severe phenotypes and more disability, higher prevalence of assisted ventilation and a shorter time of evolution to show it. The determination of prognostic factors is mandatory in order to refine the accuracy of prognostic information, to develop follow-up strategy and, more importantly, to improve the decision algorithm for enzyme replacement therapy administration. The demonstration of genotype-phenotype correlations could help to reach this objective. Clinical assessment homogeneity is required to overcome limitations due to the lack of power of most studies.

Therapeutic advances in the management of Pompe disease and other metabolic myopathies

The world of metabolic myopathies has been dramatically modified by the advent of enzyme replacement therapy (ERT), the first causative treatment for glycogenosis type II (GSDII) or Pompe disease, which has given new impetus to research into that disease and also other pathologies. This article reviews new advances in the treatment of GSDII, the consensus about ERT, and its limitations. In addition, the most recent knowledge regarding the pathophysiology, phenotype, and genotype of the disease is discussed. Pharmacological, immunotherapy, nutritional, and physical/rehabilitative treatments for late-onset Pompe disease and other metabolic myopathies are covered, including treatments for defects in glycogen metabolism, such as glycogenosis type V (McArdle disease), and glycogenosis type III (debrancher enzyme deficiency), and defects in lipid metabolism, such as carnitine palmitoyltransferase II deficiency and electron transferring flavoprotein dehydrogenase deficiency, or riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency.

Low anal sphincter tone in infantile-onset Pompe Disease: an emerging clinical issue in enzyme replacement therapy patients requiring special attention

Pompe Disease (PD) is a lysosomal storage disease caused by acid α-glucosidase deficiency. The infantile form typically results in death in the first year of life. Patient survival has improved with enzyme replacement therapy (ERT), but new complications are being recognized. We report three cases of infantile onset PD on ERT who present with a new finding of poor anal tone, a finding that requires special attention for further complications such as rectal prolapse.