Browsing by Author "Austin, Stephanie L"

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    ItemOpen Access
    A new look at an old disease: Is Pompe disease a neuromuscular disorder with CNS involvement?
    (Molecular Genetics and Metabolism, 2020-02) Korlimarla, Aditi; Chen, Steven; Austin, Stephanie L; Provenzale, James M; Kishnani, Priya S
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    A retrospective longitudinal study and comprehensive review of adult patients with glycogen storage disease type III.
    (Molecular genetics and metabolism reports, 2021-12) Hijazi, Ghada; Paschall, Anna; Young, Sarah P; Smith, Brian; Case, Laura E; Boggs, Tracy; Amarasekara, Sathya; Austin, Stephanie L; Pendyal, Surekha; El-Gharbawy, Areeg; Deak, Kristen L; Muir, Andrew J; Kishnani, Priya S

    Introduction

    A deficiency of glycogen debrancher enzyme in patients with glycogen storage disease type III (GSD III) manifests with hepatic, cardiac, and muscle involvement in the most common subtype (type a), or with only hepatic involvement in patients with GSD IIIb.

    Objective and methods

    To describe longitudinal biochemical, radiological, muscle strength and ambulation, liver histopathological findings, and clinical outcomes in adults (≥18 years) with glycogen storage disease type III, by a retrospective review of medical records.

    Results

    Twenty-one adults with GSD IIIa (14 F & 7 M) and four with GSD IIIb (1 F & 3 M) were included in this natural history study. At the most recent visit, the median (range) age and follow-up time were 36 (19-68) and 16 years (0-41), respectively. For the entire cohort: 40% had documented hypoglycemic episodes in adulthood; hepatomegaly and cirrhosis were the most common radiological findings; and 28% developed decompensated liver disease and portal hypertension, the latter being more prevalent in older patients. In the GSD IIIa group, muscle weakness was a major feature, noted in 89% of the GSD IIIa cohort, a third of whom depended on a wheelchair or an assistive walking device. Older individuals tended to show more severe muscle weakness and mobility limitations, compared with younger adults. Asymptomatic left ventricular hypertrophy (LVH) was the most common cardiac manifestation, present in 43%. Symptomatic cardiomyopathy and reduced ejection fraction was evident in 10%. Finally, a urinary biomarker of glycogen storage (Glc4) was significantly associated with AST, ALT and CK.

    Conclusion

    GSD III is a multisystem disorder in which a multidisciplinary approach with regular clinical, biochemical, radiological and functional (physical therapy assessment) follow-up is required. Despite dietary modification, hepatic and myopathic disease progression is evident in adults, with muscle weakness as the major cause of morbidity. Consequently, definitive therapies that address the underlying cause of the disease to correct both liver and muscle are needed.
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    ItemOpen Access
    Alglucosidase alfa enzyme replacement therapy as a therapeutic approach for a patient presenting with a PRKAG2 mutation.
    (Mol Genet Metab, 2017-01) Austin, Stephanie L; Chiou, Andrew; Sun, Baodong; Case, Laura E; Govendrageloo, Kenny; Hansen, Perrin; Kishnani, Priya S
    OBJECTIVE: PRKAG2 syndrome, an autosomal dominant disorder, is characterized by severe infantile hypertrophic cardiomyopathy and heart rhythm disturbances to cases with a later presentation and a spectrum of manifestations including cardiac manifestations, myopathy and seizures. The cardiac features of PRKAG2 resemble the cardiac manifestations of Pompe disease. We present a patient who was initially diagnosed with Pompe disease and treated with alglucosidase-alfa enzyme replacement therapy (ERT); however, he was eventually diagnosed to carrying a PRKAG2 pathogenic gene mutation; he did not have Pompe disease instead he was a carrier for the common adult leaky splice site mutation in the GAA gene. CASE REPORT: At 2.5months, the patient had hypotonia/generalized muscle weakness, a diagnosis of non-classic infantile Pompe disease was made based on low acid alpha-glucosidase activity and the patient started on ERT at 11months. However, 1month later, the patient began to have seizures. As the patient's medical history was somewhat unusual for infantile Pompe disease, further evaluation was initiated and included a glycogen storage disease sequencing panel which showed that the patient had a pathogenic mutation in PRKAG2 which had been reported previously. ERT was discontinued and patient had a progression of motor deficits. ERT was reinitiated by the treating physician, and a clinical benefit was noted. CONCLUSION: This report outlines the benefits of ERT with alglucosidase alfa in a patient with PRKAG2 syndrome, the decline in his condition when the ERT infusions were discontinued, and the significant positive response when ERT was reinitiated.
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    ItemOpen Access
    Behavioral, social and school functioning in children with Pompe disease
    (Molecular Genetics and Metabolism Reports, 2020-12) Korlimarla, Aditi; Spiridigliozzi, Gail A; Stefanescu, Mihaela; Austin, Stephanie L; Kishnani, Priya S
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    Beyond predicting diagnosis: Is there a role for measuring biotinidase activity in liver glycogen storage diseases?
    (Molecular genetics and metabolism reports, 2022-06) El-Gharbawy, Areeg; Tolun, Adviye A; Halaby, Carine A; Austin, Stephanie L; Kishnani, Priya S; Bali, Deeksha S

    Introduction

    Biotinidase synthesis is needed to recycle biotin for essential metabolic reactions. Biotinidase activity is lower than normal levels in advanced liver disease but is higher in hepatic glycogen storage disorders (GSDs), however the cause of this association remains unclear.

    Methods

    In this study, biotinidase activity was measured in plasma samples from 45 individuals with hepatic GSDs; GSDI (a, b; n = 25) and GSD III (a, b; n = 20), complemented by a chart review to associate biotinidase activity levels with clinical laboratory and imaging findings known to be implicated in these GSDs.

    Results

    Our findings showed variation in biotinidase activity levels among subjects with GSD I and III; biotinidase activity correlated positively with hypertriglyceridemia in subjects with GSD I (r = 0.47, P = 0.036) and GSD III (r = 0.58, P = 0.014), and correlated negatively with age (r = -0.50, P = 0.03) in patients with GSD III. Additionally, biotinidase activity was reduced, albeit within the normal range in subjects with evidence of fibrosis/cirrhosis, as compared to subjects with hepatomegaly with or without steatosis (P = 0.002).

    Discussions

    These findings suggest that abnormal lipid metabolism in GSD I and III and progressive liver disease in GSD III may influence biotinidase activity levels. We suggest that a prospective, multi-center, longitudinal study designed to assess the significance of monitoring biotinidase activity in a larger cohort with hepatic GSDs is warranted to confirm this observation.

    Take-home message

    Altered lipid metabolism and advancing liver fibrosis/cirrhosis may influence biotinidase activity levels in patients with hepatic glycogen storage disease. Thus, longitudinal monitoring of biotinidase activity, when combined with clinical and other biochemical findings may be informative.
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    ItemOpen Access
    Bulbar muscle weakness and fatty lingual infiltration in glycogen storage disorder type IIIa.
    (Molecular genetics and metabolism, 2012-11) Horvath, Jeffrey J; Austin, Stephanie L; Jones, Harrison N; Drake, Elizabeth J; Case, Laura E; Soher, Brian J; Bashir, Mustafa R; Kishnani, Priya S
    Glycogen storage disorder type III (GSD III) is a rare autosomal recessive disorder resulting from a deficiency of glycogen debranching enzyme, critical in cytosolic glycogen degradation. GSD IIIa, the most common form of GSD III, primarily affects the liver, cardiac muscle, and skeletal muscle. Although skeletal muscle weakness occurs commonly in GSD IIIa, bulbar muscle involvement has not been previously reported. Here we present three GSD IIIa patients with clinical evidence of bulbar weakness based on instrumental assessment of lingual strength. Dysarthria and/or dysphagia, generally mild in severity, were evident in all three individuals. One patient also underwent correlative magnetic resonance imaging (MRI) which was remarkable for fatty infiltration at the base of the intrinsic tongue musculature, as well as abnormal expansion of the fibro-fatty lingual septum. Additionally, we provide supportive evidence of diffuse glycogen infiltration of the tongue at necropsy in a naturally occurring canine model of GSD IIIa. While further investigation in a larger group of patients with GSD III is needed to determine the incidence of bulbar muscle involvement in this condition and whether it occurs in GSD IIIb, clinical surveillance of lingual strength is recommended.
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    Correlation between quantitative whole-body muscle magnetic resonance imaging and clinical muscle weakness in Pompe disease.
    (Muscle & nerve, 2015-05) Horvath, Jeffrey J; Austin, Stephanie L; Case, Laura E; Greene, Karla B; Jones, Harrison N; Soher, Brian J; Kishnani, Priya S; Bashir, Mustafa R

    Introduction

    Previous examination of whole-body muscle involvement in Pompe disease has been limited to physical examination and/or qualitative magnetic resonance imaging (MRI). In this study we assess the feasibility of quantitative proton-density fat-fraction (PDFF) whole-body MRI in late-onset Pompe disease (LOPD) and compare the results with manual muscle testing.

    Methods

    Seven LOPD patients and 11 disease-free controls underwent whole-body PDFF MRI. Quantitative MR muscle group assessments were compared with physical testing of muscle groups.

    Results

    The 95% upper limits of confidence intervals for muscle groups were 4.9-12.6% in controls and 6.8-76.4% in LOPD patients. LOPD patients showed severe and consistent tongue and axial muscle group involvement, with less marked involvement of peripheral musculature. MRI was more sensitive than physical examination for detection of abnormality in multiple muscle groups.

    Conclusion

    This integrated, quantitative approach to muscle assessment provides more detailed data than physical examination and may have clinical utility for monitoring disease progression and treatment response.
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    ItemOpen Access
    Natural Progression of Canine Glycogen Storage Disease Type IIIa.
    (Comp Med, 2016-02) Brooks, Elizabeth D; Yi, Haiqing; Austin, Stephanie L; Thurberg, Beth L; Young, Sarah P; Fyfe, John C; Kishnani, Priya S; Sun, Baodong
    Glycogen storage disease type IIIa (GSD IIIa) is caused by a deficiency of glycogen debranching enzyme activity. Hepatomegaly, muscle degeneration, and hypoglycemia occur in human patients at an early age. Long-term complications include liver cirrhosis, hepatic adenomas, and generalized myopathy. A naturally occurring canine model of GSD IIIa that mimics the human disease has been described, with progressive liver disease and skeletal muscle damage likely due to excess glycogen deposition. In the current study, long-term follow-up of previously described GSD IIIa dogs until 32 mo of age (n = 4) and of family-owned GSD IIIa dogs until 11 to 12 y of age (n = 2) revealed that elevated concentrations of liver and muscle enzyme (AST, ALT, ALP, and creatine phosphokinase) decreased over time, consistent with hepatic cirrhosis and muscle fibrosis. Glycogen deposition in many skeletal muscles; the tongue, diaphragm, and heart; and the phrenic and sciatic nerves occurred also. Furthermore, the urinary biomarker Glc4, which has been described in many types of GSD, was first elevated and then decreased later in life. This urinary biomarker demonstrated a similar trend as AST and ALT in GSD IIIa dogs, indicating that Glc4 might be a less invasive biomarker of hepatocellular disease. Finally, the current study further demonstrates that the canine GSD IIIa model adheres to the clinical course in human patients with this disorder and is an appropriate model for developing novel therapies.
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    ItemOpen Access
    Novel approaches to quantify CNS involvement in children with Pompe disease.
    (Neurology, 2020-06-09) Korlimarla, Aditi; Spiridigliozzi, Gail A; Crisp, Kelly; Herbert, Mrudu; Chen, Steven; Malinzak, Michael; Stefanescu, Mihaela; Austin, Stephanie L; Cope, Heidi; Zimmerman, Kanecia; Jones, Harrison; Provenzale, James M; Kishnani, Priya S
    OBJECTIVE:To characterize the extent of central nervous system involvement in children with Pompe disease using brain magnetic resonance imaging (MRI) and developmental assessments. METHODS:The study included fourteen children (ages 6-18 years) with infantile Pompe disease (IPD) (n=12) or late onset Pompe disease (LOPD) (n=2) receiving enzyme replacement therapy. White matter (WM) hyperintense foci seen in the brain MRIs were systematically quantified using the Fazekas scale (FS) grading system with a novel approach; the individual FS scores from ten anatomical areas were summed to yield a total FS score (range: absent-0 to severe-30) for each child. The FS scores were compared to developmental assessments of cognition and language obtained during the same time period. RESULTS:Mild to severe WM hyperintense foci were seen in 10/12 children with IPD (median age-10.6 years) with total FS scores ranging from 2 to 23. Periventricular, subcortical and deep WM were involved. WM hyperintense foci were seen throughout the path of the corticospinal tracts in the brain in children with IPD. Two children with IPD had no WM hyperintense foci. Children with IPD had relative weaknesses in Processing Speed, Fluid Reasoning, Visual Perception, and receptive vocabulary. The two children with LOPD had no WM hyperintense foci, and high scores on most developmental assessments. CONCLUSION:This study systematically characterized WM hyperintense foci in children with IPD; which could serve as a benchmark for longitudinal follow up of WM abnormalities in patients with Pompe disease and other known neurodegenerative disorders or leukodystrophies in children.
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    Small-fiber neuropathy in pompe disease: first reported cases and prospective screening of a clinic cohort.
    (Am J Case Rep, 2015-04-03) Hobson-Webb, Lisa D; Austin, Stephanie L; Jain, Sneha; Case, Laura E; Greene, Karla; Kishnani, Priya S
    BACKGROUND: Prior autopsy reports demonstrate glycogen deposition in Schwann cells of the peripheral nerves in patients with infantile and late-onset Pompe disease (LOPD), but little is known about associated clinical features. CASE REPORT: Here, we report the first confirmed cases of small-fiber neuropathy (SFN) in LOPD and present the results of a first attempt at screening for SFN in this patient population. After confirming small-fiber neuropathy in 2 LOPD patients, 44 consecutive Pompe patients (iOPD=7, LOPD n=37) presenting to the Duke University Glycogen Storage Disease Program between September 2013 and November 2014 were asked to complete the 21-item Small-Fiber Neuropathy Screening List (SFNSL), where a score of ≥11 is considered to be a positive screen. Fifty percent of patients had a positive SFN screen (mean score 11.6, 95% CI 9.0-14.2). A modest correlation between the SFNSL score and current age was seen (r=0.38, p=0.01), along with a correlation with duration of ERT (r=0.31, p=0.0495). Trends toward correlation with forced vital capacity and age at diagnosis were also present. Women had a higher mean SFNSL score (14.2) than men (8.2, p=0.017). CONCLUSIONS: SFN may occur in association with Pompe disease and precede the diagnosis. Further studies are needed to determine its true prevalence and impact.