Dramatic advances in recent years in the diagnosis and treatment of inborn errors of metabolism (IEM) make it imperative for the physician to be both aware of their occurrence and acquainted with their clinical presentations. Many may present with symptoms and signs common to sick infants, such as refusal to feed, vomiting and convulsions. Failure to include IEM in the differential diagnosis may have grave consequences, because only prompt recognition and appropriate treatment of a metabolic crisis can help prevent irreversible brain damage or death. We describe a 3-week-old female infant, eventually diagnosed as having an IEM (3-hydroxy-3-methyl-glutaric aciduria), who was admitted to various hospitals and died during her last admission. We focused on the clinical and laboratory findings of each of the first 2 admissions which might have provided clues to the true nature of the illness had the clinicians been aware of the possibility of IEM. Patients with IEM are generally managed in specialized centers; however, the responsibility for initial recognition and immediate treatment of a metabolic emergency lies with the primary physician. The purpose of our case presentation and the discussion of the lessons derived from it, is to prompt the clinician to an awareness and understanding of a subject that used to be considered reserved for specialists. In fact, all that is needed is clinical alertness and the performance of certain well-focused, simple laboratory tests for IEM.