A 32-year-old man with glutathione synthetase deficiency developing an acute metabolic crisis is described. During this acute episode, intracellular glutathione content in erythrocytes was below the detection limit (<0.3 mmol/L). Leukotriene C4 in CSF and urinary leukotriene E4 were massively decreased, indicating an imparied synthesis of cysteinyl leukotrienes. Clinical recovery after one week was accompanied by a clear improvement of these biochemical parameters. The highly disturbed glutathione synthesis is postulated to be the reason for a deficient synthesis of cysteinyl leukotrienes, which may at least in part be responsible for the severe clinical symptoms.