Infantile extreme hypertriglyceridemia diagnosed as glycogen storage disease type Ia: A case report

Rationale: Glycogen storage disease type Ia (GSD Ia) typically presents with fasting hypoglycemia and hyperlipidemia. Atypical infantile presentations can delay diagnosis. We report an infant with extreme hypertriglyceridemia ultimately diagnosed as GSD Ia. Patient concerns: A 5-month-old girl presented with poor appetite, growth retardation, hepatomegaly, and extreme hypertriglyceridemia (72 mmol/L), hypercholesterolemia, elevated transaminases, hyperuricemia, and hyperlactatemia, but initial normal blood glucose. Diagnoses: Initial differentials included familial hypertriglyceridemia, but metabolic screening was normal. Whole-exome sequencing confirmed GSD Ia with compound heterozygous G6PC mutations (c.648G>T and c.814G>T). Interventions: Initial lipid-lowering (low-fat diet, fenofibrate, omega-3, plasma exchange) reduced triglyceride. Post-diagnosis, she received lactose-free formula with frequent feeds and nocturnal nutrition; uncooked cornstarch was introduced at 6 months, though adherence was initially poor. Outcomes: Metabolic control was unstable until age 2 due to poor adherence. After 24 months of structured cornstarch therapy, fasting glucose normalized (4.2–6.6 mmol/L), triglycerides decreased (1.8–6.7 mmol/L), and catch-up growth occurred (height Z-score from -3.9 to -2.2 by 36 months). Lessons: GSD Ia should be considered in infantile extreme hypertriglyceridemia with growth retardation, even without classic hypoglycemia. Sustained metabolic control requires multidisciplinary strategies addressing both biochemical and adherence barriers.