Phosphoglucomutase 1 (PGM1) catalyzes the reversible interconversion of α-D-glucose 1-phosphate and α-D-glucose 6-phosphate, a reaction essential for carbohydrate metabolism 1. This bidirectional conversion proceeds via the intermediate α-D-glucose 1,6-bisphosphate and connects glycogen metabolism with glucose utilization pathways 1. PGM1 additionally participates in cytoplasmic biosynthesis of nucleotide sugars required for glycan biosynthesis, bridging carbohydrate and protein glycosylation pathways 12. PGM1 deficiency causes phosphoglucomutase 1 congenital disorder of glycosylation (PGM1-CDG), a multisystem disease previously classified as glycogen storage disorder XIV 3. Clinical manifestations include cleft palate, hepatic dysfunction, hypoglycemia, myopathy, and life-threatening dilated cardiomyopathy 34. Notably, neurological involvement occurs in approximately 41% of reported cases and can manifest independently of hypoglycemia 5. Unlike most CDG disorders, PGM1-CDG responds to oral d-galactose supplementation, which improves liver, endocrine, and coagulation abnormalities 3. However, galactose therapy does not prevent cardiomyopathy, which remains the primary life-threatening complication 4. Recent therapeutic approaches including AAV-mediated gene replacement show promise in preventing and halting cardiac disease progression in animal models 4.