Despite the abundance of reports emerging in the literature on metabolic disorders, some disorders remain undiagnosed or misdiagnosed, not only in clinical pathology but also in forensic pathology. The authors report a patient who had recurrent episodes characterized by nausea, vomiting, and signs of dehydration necessitating admission to the hospital. At each admission, he was found to have lactic acidosis. On the first admission, glycolic acid was detected in his blood and he was diagnosed as having ethylene glycol intoxication. Only at the third admission, 2 years after the first, was the possibility of an underlying metabolic disorder considered. Laboratory investigations showed a deficiency of complex I in the mitochondrial oxidative phosphorylation. Possible medicolegal implications are discussed.