September 2026 Research Update

This months treatment-focused studies added a clearer picture of why the same enzyme replacement therapy can work differently across people. Across small cohorts, two factors stood out: the immune system (especially anti-drug antibodies) and supportive approaches used alongside enzyme therapy. The evidence is early and not meant to prove cause-and-effect, but it helps explain sources of variability patients and families may already notice. [1] [2] [3]

In classic infantile Pompe disease, higher anti-drug antibody (ADA) levels were often linked to less enzyme available in the body after an infusion of alglucosidase alfa (the standard enzyme replacement therapy). In 6 of 9 people with high antibody levels, laboratory tests found evidence that the antibodies affected the enzyme treatment: blood-based measurements showed reduced enzyme exposure in 5, and cell experiments found reduced enzyme activity inside cells in 5. This supports the idea that in some patients, immune responses can directly interfere with how much enzyme is actually usable. [1]

A separate immune-profiling study looked at enzyme therapy combined with transient low-dose methotrexate (a short-term immune-suppressing approach) in infantile-onset and late-onset Pompe disease. The researchers reported shifts in immune cell patterns after treatment that looked less inflammatory, and they also saw the urine marker Glc4 (a marker related to glycogen breakdown) decrease after treatment. Even so, a subset of patients still developed or increased anti-rhGAA antibodies, while several late-onset patients maintained long-term tolerance, showing that immune responses remain variable. [2]

In a 12-person case series (11 also on enzyme therapy, 1 on the diet alone), a carbohydrate-restricted, high-fat, high-protein diet was reported to be feasible and generally well tolerated over a median follow-up of about 2 years. The group showed stabilization or mild-to-moderate improvements in motor function and endurance, and creatine kinase (CK, a blood marker linked to muscle damage) decreased early on. Because this was not a controlled comparison, it cannot show what would have happened without the diet, but it adds to ongoing research interest in nutrition as a supportive piece of care. [3]

For patients and caregivers, these studies help clarify why response to enzyme replacement therapy can differ, even when treatment looks similar on paper. The antibody study suggests that for some infantile-onset patients, very high antibody levels may mean less enzyme is available after infusions, while other patients with antibodies may not show the same effect. The methotrexate immune-profiling and diet case series are early signals that add-on approaches can change lab measures and may relate to function, but they do not establish what will help which person. For now, this body of work mainly adds understanding that may guide future research on how to personalize enzyme therapy and supportive strategies. [1] [2] [3]

This months prognosis-focused studies showed that some important Pompe-related complications can appear later in childhood, even in people treated early. Across cohorts of infantile-onset Pompe disease, sleep-related breathing changes and brain involvement were both described as issues that may emerge around school age or later. These reports do not mean every child will develop these problems, but they make the long-term picture more concrete for families planning for ongoing follow-up. [4] [5]

In 16 early-treated infantile-onset patients identified by newborn screening, overnight sleep testing found that many developed moderate obstructive sleep apnea over time. Sleep breathing abnormalities often appeared around age 7 to 8, and changes in breathing during sleep could occur even when motor function or breathing test results looked relatively preserved. Children who became non-ambulatory showed faster worsening in forced vital capacity (a breathing test) and in the sleep apnea measure. [4]

A separate international series described epilepsy as part of the brain and nervous system involvement in classic infantile Pompe disease. Seizures typically began after age 7, were often focal (starting in one part of the brain), and brain imaging commonly showed widespread white matter changes; cognitive impairment was also frequent in those tested. About 70% were reported to become seizure-free with antiseizure medications, and a blood marker of nerve injury (NfL) was elevated in those measured, supporting ongoing central nervous system involvement. [5]

For families, these studies add clarity that monitoring in infantile-onset Pompe disease may need to keep pace with changing needs over many years, not just early childhood. The sleep study indicates that breathing problems during sleep can show up before obvious daytime breathing decline, while the epilepsy report shows that seizures and brain imaging changes may appear later in childhood in some individuals. These findings may matter now in terms of awareness and conversations about long-term follow-up plans, but they do not predict what will happen in any one child. What remains uncertain is how common these issues are across all early-treated children and which early signs best predict who will be affected. [4] [5]

This months diagnosis-focused studies showed both the power and the limits of screening and follow-up testing. Newborn screening continues to identify babies labeled as presumed late-onset Pompe disease, but confirming what a positive screen means can be complex. In contrast, screening adults in sleep clinics did not confirm any definite late-onset cases in the tested group, suggesting that broad screening of that setting alone may not yield many diagnoses. [6] [7]

In North Carolinas newborn screening program over 20 months, 52 infants screened positive and 18 were diagnosed with presumed late-onset Pompe disease after follow-up testing, with no infantile-onset cases identified in that period. The researchers evaluated screening-related biomarkers and reported that one ratio (GAA to another enzyme) aligned with final designations, while another ratio was eliminated from use. They also noted that the age at which the blood spot was collected affected measured enzyme activity, and they proposed two step-by-step algorithms to speed early decisions and later final classification after a positive screen. [6]

In a prospective Japanese study of 724 people referred for sleep testing due to suspected sleep-disordered breathing, dried blood spot screening did not lead to any confirmed late-onset Pompe diagnoses among those who completed confirmatory testing. Seven people screened positive but declined confirmatory testing, leaving some uncertainty about the exact prevalence in this group. The study could not identify predictive factors for Pompe in this setting, partly because recruitment fell short of the intended sample size. [7]

Two additional studies addressed testing in more indirect ways: one evaluated heart imaging and one evaluated gene changes in the lab. In 8 adults with late-onset Pompe disease, a specialized ultrasound measurement of heart muscle motion was reduced despite normal standard echocardiography, suggesting a possible way to detect subtle heart involvement earlier. In laboratory work, a cell-based test measured how 42 different GAA gene missense variants affected enzyme activity, and about two-thirds fell below cutoffs suggesting a harmful effect, with examples where the functional results helped interpret uncertain genetic findings. [8] [9]

For patients and caregivers, these studies help explain why a positive screen or a genetic result often leads to additional steps rather than an immediate clear answer. The newborn screening report shows that programs may identify many babies thought to be at risk for later-onset disease, and that details like collection timing and which biomarker ratios are used can influence classification. The sleep-clinic screening study suggests that testing everyone in that setting did not uncover confirmed late-onset Pompe disease in this sample, so the best ways to find undiagnosed adults remain uncertain. The heart imaging and gene-variant lab studies may matter later by improving how subtle disease involvement or uncertain gene changes are interpreted, but these tools are still being defined and are not direct measures of symptoms or day-to-day function. [6] [7] [8] [9]