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

Abstract BACKGROUND Deficiency of the lysosomal enzyme acid α-glucosidase (GAA) causes Pompe disease. Newborn screening for Pompe disease is ongoing, and improved methods for distinguishing affected patients from those with pseudodeficiency, especially in the Asian population, would substantially reduce the number of patient referrals for clinical follow-up. METHODS We measured the enzymatic activity of GAA in dried blood spots on newborn screening cards (DBS) using a tandem mass spectrometry (MS/MS) assay. The assay displayed a relatively large analytical range compared to the fluorimetric assay with 4-methylumbelliferyl-α-glucoside. DBS from newborns confirmed to have infantile-onset Pompe disease (IOPD, n = 11) or late-onset Pompe disease (LOPD) (n = 12) and those from patients bearing pseudodeficiency alleles with or without Pompe mutations, or Pompe disease carriers (n = 230) were studied. RESULTS With use of the MS/MS GAA assay in DBS, 96% of the pseudodeficiency newborns and all of the Pompe disease carriers were well separated from the IOPD and LOPD newborns. The fluorimetric assay separated <10% of the pseudodeficiencies from the IOPD/LOPD group. CONCLUSIONS The relatively large analytical range MS/MS GAA assay but not the fluorimetric assay in DBS provides a robust approach to reduce the number of referrals and should dramatically facilitate newborn screening of Pompe disease.

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Baseline Urinary Glucose Tetrasaccharide Concentrations in Patients with Infantile- and Late-Onset Pompe Disease Identified by Newborn Screening

JIMD Reports - JIMD Reports, Volume 19 ◽

10.1007/8904_2014_366 ◽

2014 ◽

pp. 67-73 ◽

Cited By ~ 14

Author(s):

Yin-Hsiu Chien ◽

Jennifer L. Goldstein ◽

Wuh-Liang Hwu ◽

P. Brian Smith ◽

Ni-Chung Lee ◽

...

Keyword(s):

Newborn Screening ◽

Pompe Disease ◽

Late Onset ◽

Urinary Glucose ◽

Glucose Tetrasaccharide

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Homozygosity for the common GAA gene splice site mutation c.-32-13T>G in Pompe disease is associated with the classical adult phenotypical spectrum

Neuromuscular Disorders ◽

10.1016/j.nmd.2015.07.002 ◽

2015 ◽

Vol 25 (9) ◽

pp. 719-724 ◽

Cited By ~ 19

Author(s):

Olimpia Musumeci ◽

Andrea Thieme ◽

Kristl G. Claeys ◽

Stephan Wenninger ◽

Rudolf A. Kley ◽

...

Keyword(s):

Splice Site ◽

Pompe Disease ◽

Splice Site Mutation ◽

Site Mutation ◽

The Common ◽

C 32 ◽

Gaa Gene

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Liquid Chromatography–Tandem Mass Spectrometry Assay of Leukocyte Acid α-Glucosidase for Post-Newborn Screening Evaluation of Pompe Disease

Clinical Chemistry ◽

10.1373/clinchem.2016.259036 ◽

2017 ◽

Vol 63 (4) ◽

pp. 842-851 ◽

Cited By ~ 10

Author(s):

Na Lin ◽

Jingyu Huang ◽

Sara Violante ◽

Joseph J Orsini ◽

Michele Caggana ◽

...

Keyword(s):

Newborn Screening ◽

Pompe Disease ◽

Late Onset ◽

Treatment Options ◽

Internal Standard ◽

Lysosomal Storage ◽

Blood Samples ◽

Liquid Chromatography Tandem Mass ◽

Progressive Weakness

Abstract BACKGROUND Pompe disease (PD) is the first lysosomal storage disorder to be added to the Recommended Uniform Screening Panel for newborn screening. This condition has a broad phenotypic spectrum, ranging from an infantile form (IOPD), with severe morbidity and mortality in infancy, to a late-onset form (LOPD) with variable onset and progressive weakness and respiratory failure. Because the prognosis and treatment options are different for IOPD and LOPD, it is important to accurately determine an individual's phenotype. To date, no enzyme assay of acid α-glucosidase (GAA) has been described that can differentiate IOPD vs LOPD using blood samples. METHODS We incubated 10 μL leukocyte lysate and 25 μL GAA substrate and internal standard (IS) assay cocktail for 1 h. The reaction was purified by a liquid–liquid extraction. The extracts were evaporated and reconstituted in 200 μL methanol and analyzed by LC-MS/MS for GAA activity. RESULTS A 700-fold higher analytical range was observed with the LC-MS/MS assay compared to the fluorometric method. When GAA-null and GAA-containing fibroblast lysates were mixed, GAA activity could be measured accurately even in the range of 0%–1% of normal. The leukocyte GAA activity in IOPD (n = 4) and LOPD (n = 19) was 0.44–1.75 nmol · h−1 · mg−1 and 2.0–6.5 nmol · h−1 · mg−1, respectively, with no overlap. The GAA activity of pseudodeficiency patients ranged from 3.0–28.1 nmol · h−1 · mg−1, showing substantial but incomplete separation from the LOPD group. CONCLUSIONS This assay allows determination of low residual GAA activity in leukocytes. IOPD, LOPD, and pseudodeficiency patients can be partially differentiated by measuring GAA using blood samples.

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Newborn Screening for Pompe Disease: Pennsylvania Experience

International Journal of Neonatal Screening ◽

10.3390/ijns6040089 ◽

2020 ◽

Vol 6 (4) ◽

pp. 89

Author(s):

Can Ficicioglu ◽

Rebecca C. Ahrens-Nicklas ◽

Joshua Barch ◽

Sanmati R. Cuddapah ◽

Brenda S. DiBoscio ◽

...

Keyword(s):

Enzyme Activity ◽

Newborn Screening ◽

Pompe Disease ◽

Late Onset ◽

Compound Heterozygous ◽

Variant Of Unknown Significance ◽

Unknown Significance ◽

Second Tier ◽

Alpha Glucosidase ◽

Gaa Gene

Pennsylvania started newborn screening for Pompe disease in February 2016. Between February 2016 and December 2019, 531,139 newborns were screened. Alpha-Glucosidase (GAA) enzyme activity is measured by flow-injection tandem mass spectrometry (FIA/MS/MS) and full sequencing of the GAA gene is performed as a second-tier test in all newborns with low GAA enzyme activity [<2.10 micromole/L/h]. A total of 115 newborns had low GAA enzyme activity and abnormal genetic testing and were referred to metabolic centers. Two newborns were diagnosed with Infantile Onset Pompe Disease (IOPD), and 31 newborns were confirmed to have Late Onset Pompe Disease (LOPD). The incidence of IOPD + LOPD was 1:16,095. A total of 30 patients were compound heterozygous for one pathogenic and one variant of unknown significance (VUS) mutation or two VUS mutations and were defined as suspected LOPD. The incidence of IOPD + LOPD + suspected LOPD was 1: 8431 in PA. We also found 35 carriers, 15 pseudodeficiency carriers, and 2 false positive newborns.

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Two-Tiered Newborn Screening with Post-Analytical Tools for Pompe Disease and Mucopolysaccharidosis Type I Results in Performance Improvement and Future Direction

International Journal of Neonatal Screening ◽

10.3390/ijns6010002 ◽

2020 ◽

Vol 6 (1) ◽

pp. 2 ◽

Cited By ~ 5

Author(s):

Patricia L. Hall ◽

Rossana Sanchez ◽

Arthur F. Hagar ◽

S. Caleb Jerris ◽

Angela Wittenauer ◽

...

Keyword(s):

Newborn Screening ◽

Pompe Disease ◽

Late Onset ◽

Screening Program ◽

Molecular Testing ◽

Type I ◽

Mucopolysaccharidosis Type ◽

Mucopolysaccharidosis Type I ◽

Analytical Tools ◽

Mps I

We conducted a pilot newborn screening (NBS) study for Pompe disease (PD) and mucopolysaccharidosis type I (MPS I) in the multiethnic population of Georgia. We screened 59,332 infants using a two-tier strategy of flow injection tandem mass spectrometry (FIA-MSMS) enzyme assays. The first tier of testing was a 2-plex assay measuring PD and MPS I enzyme activity, followed by a second-tier test with additional enzymes to improve specificity. Interpretation of results was performed using post-analytical tools created using Collaborative Laboratory Integrated Reports (CLIR). We identified a single case of infantile onset PD, two cases of late onset PD, and one pseudodeficiency. The positive predictive value (PPV) for PD screening during the study was 66.7%. No cases of MPS I were identified during the study period, but there were 2 confirmed cases of pseudodeficiency and 6 cases lost to follow up. The two-tier screening strategy was successful in reducing false positive results and allowed for the identification and early treatment of a case of infantile PD but the frequency of pseudodeficiency in MPS I is problematic. Molecular testing is required and should be covered by the screening program to avoid delays in case resolution.

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