Glycogen-storage and carbohydrate metabolism disorders — branching viva

A six-month-old boy presents with marked hepatomegaly, growth faltering and an early-morning seizure. A fasted blood sample shows glucose 1.8 mmol/L, lactate 7.2 mmol/L, urate 0.52 mmol/L, triglycerides 9.1 mmol/L and low ketones. The examiner asks: what is the diagnosis, how does the biochemical tetrad arise from the enzyme block, how do you confirm it, what is the cornerstone of long-term management, and what long-term complications must you surveil for — then branches to a three-month-old with hypotonia, macroglossia, a creatine kinase of 4200 and concentric left ventricular hypertrophy, and asks you to explain why Pompe does not cause hypoglycaemia, why enzyme replacement works, and how galactosaemia differs as a toxic-sugar disorder.