We report elevated urinary excretion of 3-methylglutaconic (3MGC) and 3-methylglutaric acids (3MGR) in a patient with glycogen storage disease Ib. Combined excretion was 10-fold elevated in comparison to control during inadequate glucose maintenance, and still elevated following dietary improvement. 3MGC acid excretion correlated with plasma lactate and glucose. We speculate that imbalanced gluconeogenesis and de novo cholesterol synthesis result in secondarily increased 3MGC/3MGR production.
