Defect in Dimethylglycine Dehydrogenase, a New Inborn Error of Metabolism: NMR Spectroscopy Study

Abstract Background: A38-year-old man presented with a history of fish odor (since age 5) and unusual muscle fatigue with increased serum creatine kinase. Our aim was to identify the metabolic error in this new condition. Methods: We used 1H NMR spectroscopy to study serum and urine from the patient. Results: The concentration of N,N-dimethylglycine (DMG) was increased ∼100-fold in the serum and ∼20-fold in the urine. The presence of DMG as a storage product was confirmed by use of 13C NMR spectroscopy and gas chromatography–mass spectrometry. The high concentration of DMG was caused by a deficiency of the enzyme dimethylglycine dehydrogenase (DMGDH). A homozygous missense mutation was found in the DMGDH gene of the patient. Conclusions: DMGDH deficiency must be added to the differential diagnosis of patients complaining of a fish odor. This deficiency is the first inborn error of metabolism discovered by use of in vitro 1H NMR spectroscopy of body fluids.