Longitudinal Characterization of Males With X-Linked Creatine Transporter Deficiency: Final Results of a Multiyear Observational Study.
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2026-02
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The purpose of the Vigilan observational study (ClinicalTrials.gov, NCT02931682) was to prospectively assess the natural history and developmental course of creatine transporter deficiency (CTD).Methods
Males with CTD aged 6 months to 65 years were evaluated at 6-month intervals for up to 4 years. Evaluations included neurodevelopmental assessments of intellectual functioning, adaptive functioning, challenging behaviors and the onset and progression of medical comorbidities.Results
Fifty participants (median age, 7.6 years) were enrolled. The predominant CTD phenotype consisted of significant intellectual disabilities and limited skill development over time. Most participants had a history of febrile or nonfebrile seizures, gastrointestinal symptoms, and growth failure. All participants learned how to walk, 78% developed at least some verbal speech, and 34% communicated using phrases or sentences. Norm-referenced neurodevelopment assessments indicated declining standardized scores over time; however, absolute scores (i.e., age equivalent person ability scores) indicated that developmental gains were slower than average, particularly among older participants. Between-person differences in neurodevelopmental skills as a function of age did not match within-person change, suggesting a cohort effect.Conclusions
In this cohort, CTD was associated with significant and persistent intellectual disability. The use of absolute metrics from neurodevelopmental tests (e.g., person ability scores) allowed for the quantification of slow, but present, skill development.Type
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Miller, Judith S, Cristan Farmer, Susan Blair, Simona Bianconi, Natacha Akshoomoff, Irina Anselm, Bruce A Barshop, Lindsey Becker, et al. (2026). Longitudinal Characterization of Males With X-Linked Creatine Transporter Deficiency: Final Results of a Multiyear Observational Study. Pediatric neurology, 175. pp. 8–18. 10.1016/j.pediatrneurol.2025.10.023 Retrieved from https://hdl.handle.net/10161/34781.
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Scholars@Duke
Kathryn E. Gustafson
My scholarly interests and expertise are in pediatric neurodevelopmental outcomes assessment and research as well as child and parent coping with chronic childhood illness. In the 1990s, I collaborated with Dr. Robert Thompson in investigating the transactional biopsychosocial model of adaptation to pediatric conditions in children and families. Our research program was funded by the NIH and culminated in the publication of our book, Adaptation to Chronic Childhood Illness. Since that time, I have worked closely with the Division of Neonatology and the Duke Neonatal-Perinatal Research Unit on neurodevelopmental outcomes research with high-risk infants, toddlers, and school-age children. I am a gold standard psychology consultant to the Neonatal Research Network (NRN) of the NIH/NICHD, train and certify psychologists nationally and internationally in infant and toddler developmental assessment for numerous research groups, and serve as consultant for protocol development. In addition, I collaborate with colleagues in Pediatric Ophthalmology to investigate preterm optic nerve anatomy assessed via optical coherence tomography imaging and the association with neurodevelopment. I am also involved in investigations of umbilical cord blood stem cell transplant for young children with hypoxic ischemic encephalopathy, cerebral palsy, and inborn errors of metabolism, such as Krabbe disease, with colleagues in the Pediatric Transplant and Cellular Therapy program.
Dwight D. Koeberl
As a physician-scientist practicing clinical and biochemical genetics, I am highly motivated to seek improved therapy for my patients with inherited disorders of metabolism. The focus of our research has been the development of gene therapy with adeno-associated virus (AAV) vectors, most recently by genome editing with CRISPR/Cas9. We have developed gene therapy for inherited disorders of metabolism, especially glycogen storage disease (GSD) and phenylketonuria (PKU).
1) GSD Ia: Glucose-6-phosphatase (G6Pase) deficient animals provide models for developing new therapy for GSD Ia, although early mortality complicates research with both the murine and canine models of GSD Ia. We have prolonged the survival and reversed the biochemical abnormalities in G6Pase-knockout mice and dogs with GSD type Ia, following the administration of AAV8-pseudotyped AAV vectors encoding human G6Pase. More recently, we have performed genome editing to integrate a therapeutic transgene in a safe harbor locus for mice with GSD Ia, permanently correcting G6Pase deficiency in the GSD Ia liver. Finally, we have identified reduced autophagy as an underlying hepatocellular defect that might be treated with pro-autophagic drugs in GSD Ia.
2) GSD II/Pompe disease: Pompe disease is caused by the deficiency of acid-alpha-glucosidase (GAA) in muscle, resulting in the massive accumulation of lysosomal glycogen in striated muscle with accompanying weakness. While enzyme replacement has shown promise in infantile-onset Pompe disease patients, no curative therapy is available. We demonstrated that AAV vector-mediated gene therapy will likely overcome limitations of enzyme replacement therapy, including formation of anti-GAA antibodies and the need for frequent infusions. We demonstrated that liver-restricted expression with an AAV vector prevented antibody responses in GAA-knockout mice by inducing immune tolerance to human GAA. Antibody responses have complicated enzyme replacement therapy for Pompe disease and emphasized a potential advantage of gene therapy for this disorder. The strategy of administering low-dose gene therapy prior to initiation of enzyme replacement therapy, termed immunomodulatory gene therapy, prevented antibody formation and increased efficacy in Pompe disease mice. We are currently conducting a Phase I clinical trial of immunomodulatory gene therapy in adult patients with Pompe disease. Furthermore, we have developed drug therapy to increase the receptor-mediated uptake of GAA in muscle cells, which provides adjunctive therapy to more definitively treat Pompe disease.
3) PKU: In collaboration with researchers at OHSU, we performed an early gene therapy experiment that demonstrated long-term biochemical correction of PKU in mice with an AAV8 vector. PKU is a very significant disorder detected by newborn screening and currently inadequately treated by dietary therapy. Phenylalanine levels in mice were corrected in the blood, and elevated phenylalanine causes mental retardation and birth defects in children born to affected women, and gene therapy for PKU would address an unmet need for therapy in this disorder.
Currently we are developing methods for genome editing that will stably correct the enzyme deficiency in GSD Ia and in Pompe disease. Our long-term goal is to develop efficacious genome editing for glycogen storage diseases, which will allow us to treat these conditions early in life with long-term benefits.
Gail A. Spiridigliozzi
Cholinergic therapy in children and adolescents with Down syndrome; premutation carriers of fragile X syndrome; cognitive development of children with infantile-onset Pompe disease who are being treated with enzyme replacement therapy.
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