Failure to thrive: when to suspect inborn errors of metabolism.

Failure to thrive (FTT) is a common symptom, not a diagnosis, of a wide range of childhood diseases. Although FTT is usually caused by inadequate energy intake in diet or constitutional small size, organic pathology should be considered in some cases of FTT. This article is intended to guide primary care physicians for when to suspect inborn errors of metabolism in children who present with FTT.