title: Baseline Urinary Glucose Tetrasaccharide Concentrations in Patients with Infantile- and Late-Onset Pompe Disease Identified by Newborn Screening.
abstract: OBJECTIVE
  The urinary glucose tetrasaccharide, Glcα1-6Glcα1-4Glcα1-4Glc (Glc4), is a biomarker of glycogen accumulation and tissue damage and is elevated in patients with Pompe disease. We report baseline urinary Glc4 concentrations for patients with classic infantile-onset or late-onset Pompe disease, and those with a pseudodeficiency of acid alpha-glucosidase (GAA), identified through newborn screening (NBS) in Taiwan.
  
  
  METHODS
  Infants identified through NBS with (1) classic infantile-onset Pompe disease (NBS-IOPD) (n = 7) defined as patients with evidence for hypertrophic cardiomyopathy by EKG, X-ray, and echocardiogram, (2) a late-onset phenotype (NBS-LOPD) (n = 13) defined as patients without evidence for cardiomyopathy, (3) a GAA pseudodeficiency (n = 58), and (4) one patient with LOPD diagnosed in infancy due to family history were consented to the study. Four infants diagnosed after the onset of clinical symptoms (CLIN-IOPD) were included for comparison. Glc4 concentrations in dried urine samples on filter paper were determined using tandem mass spectrometry.
  
  
  RESULTS
  Baseline Glc4 concentrations were at or above the 90th centile of the age-matched reference range for the NBS-IOPD cohort. The median Glc4 level for this group was lower than that of the CLIN-IOPD group, although not at the level of significance (p = 0.07), but was significantly higher than that of the NBS-LOPD group (p < 0.05). Baseline Glc4 was not elevated for the NBS-LOPD and GAA pseudodeficiency cohorts and remained low for late-onset patients that did not require treatment before the age of three years.
  
  
  CONCLUSIONS
  Baseline urinary Glc4 is elevated in neonates with infantile-onset Pompe disease identified through NBS.
authors: Department of Pediatrics and Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan.
authors: Yin-Hsiu
authors: YH
authors: Chien
authors: Jennifer L
authors: JL
authors: Goldstein
authors: Wuh-Liang
authors: WL
authors: Hwu
authors: P Brian
authors: PB
authors: Smith
authors: Ni-Chung
authors: NC
authors: Lee
authors: Shu-Chuan
authors: SC
authors: Chiang
authors: Adviye A
authors: AA
authors: Tolun
authors: Haoyue
authors: H
authors: Zhang
authors: Amie E
authors: AE
authors: Vaisnins
authors: David S
authors: DS
authors: Millington
authors: Priya S
authors: PS
authors: Kishnani
authors: Sarah P
authors: SP
authors: Young