Purpose Enzyme replacement therapy (ERT) with recombinant human GAA (rhGAA) prolongs survival in infantile Pompe disease (IPD). However, the majority of cross reactive immunologic material (CRIM)-negative (CN) patients have immune responses with significant clinical decline despite continued ERT. We aimed to characterize immune responses in CN IPD patients receiving ERT monotherapy. Methods A chart review identified 20 CN IPD patients treated with ERT monotherapy for ≥6 months. Patients were stratified by anti-rhGAA antibody titers: high sustained antibody titers (HSAT) ≥51,200 at least twice; low titers (LT) <6,400 throughout treatment; or sustained intermediate titers (SIT) 6,400–25,600. Results Despite early initiation of treatment, the majority (85%) of CN patients developed significant antibody titers, most with HSAT associated with invasive ventilation and death. Nearly all patients with HSAT had at least one nonsense GAA mutation, while the LT group exclusively carried splice site or frameshift mutations. Only one patient in the HSAT group is currently alive after successful immune modulation in the entrenched setting. Conclusion Immunological responses are a significant risk in CN IPD; thus, immune tolerance induction in the naïve setting should strongly be considered. Further exploration of factors influencing immune responses is required, particularly with the advent of newborn screening for Pompe disease.

Whole-body magnetic resonance imaging (WBMRI) has clinical utility in measuring the amount of fatty infiltration in late-onset Pompe disease (LOPD). Muscle strength and function testing also provide valuable insight to the progression of myopathy seen in these patients. The main purpose of this study was to determine how closely muscle strength and functional testing correlate to the amount of fatty infiltration seen on WBMRI. LOPD patients were followed longitudinally and WBMRI, muscle strength testing using the modified Medical Research Council (mMRC) scale, muscle function testing using the Gait, Stairs, Gowers, Chair (GSGC) score, and labs including urinary glucose tetrasaccharide (Glc4) were performed at each visit. The amount of fat seen on WBMRI was quantified using proton density fat fraction (PDFF) and correlated to appropriate muscle strength and functional tests. Nineteen patients with LOPD aged 10 to 67 years were followed for a 1 to 2 year duration. There was a small increase of 1.26% (±2.57%) in overall PDFF per year in patients on ERT. Muscle strength (mMRC) and functional testing (GSGC) correlated highly with PDFF (r = −.7596, P < .0001 and r = .8267, P < .0001, respectively). Time to carry out individual tasks of the GSGC also correlated highly with PDFF of the muscles involved. Glc4 levels were normal on most visits (27/39) despite varying severity of muscle weakness in patients. Muscle strength and GSGC scores correlate highly with PDFF values from WBMRI. They may be used in assessing severity of muscle disease and to follow LOPD patients over time.

This study examines the long-term cognitive and academic outcomes of 11 individuals with infantile onset Pompe disease (IOPD) (median age = 11 years, 1 month, range = 5 years, 6 months through 17 years of age) treated with enzyme replacement therapy from an early age. All participants (7 males, 4 females) were administered individual intelligence tests (Wechsler or Leiter scales or both), a measure of their academic skill levels (Woodcock-Johnson Tests of Achievement), and a screening measure of visual-motor integration ability (Beery-Buktenica). Consistent with our earlier findings, median IQ scores for the entire group on the Wechsler (median = 84) and Leiter (median = 92) scales continue to fall at the lower end of the average range compared to same-aged peers. The median scores for the group on a measure of visual-motor integration (median = 76), visual perception (median = 74) and motor coordination (median = 60) were below average. Two distinct sub-groups emerged based on participants’ average or below average performance on the majority of academic sub-tests. Those participants with below average academic skills (n = 6) demonstrated average nonverbal cognitive abilities on the Leiter, but had weaknesses in speech and language skills and greater medical involvement. Their profiles were more consistent with a learning disability diagnosis than an intellectual disability. Two of these participants showed a significant decline (15 and 23 points, respectively) on repeated Wechsler scales, but one continued to earn average scores on the Leiter scales where the verbal and motor demands are minimal. Participants with average academic skills (n = 5) demonstrated average cognitive abilities (verbal and nonverbal) on the Wechsler scales and less medical involvement. Their speech and language skills appeared to be more intact. However, both groups earned below average median scores on the Beery-Buktenica motor coordination task. This study highlights the importance of using appropriate tests to capture both verbal and nonverbal abilities, considering each individual’s motor skills, speech and language abilities, hearing status and native language. This will allow for a more accurate assessment of whether there is a learning disability or an intellectual disability. Long-term outcomes may be related to the stability of an individual’s expressive and/or receptive language abilities over time. Changes in the speech and language domain may account for the decline in IQ observed in some IOPD long-term survivors, reflecting a learning disability rather than a decline in overall cognition or an intellectual disability. These observations, in conjunction with neuroimaging, will further our understanding of the neurocognitive profile of long-term IOPD survivors.

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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.