Failure to Thrive in a 2-month-old Boy

A 2-month-old boy presents with failure to thrive (FTT). He was born at 40 weeks’ gestation after an uncomplicated pregnancy with regular prenatal care. His birthweight was 3,884 g. He was discharged on the second day after birth. Since delivery he has had consistently poor growth. He is fed either human milk or formula every 2 to 3 hours but often loses interest before finishing a feed. His mother accurately describes an appropriate recipe for formula preparation. He has no history of significant emesis. He has approximately 2 stools daily that are normal in consistency and color. He has never had difficulty breathing or cyanotic color changes. There are no recent illnesses or sick contacts. He is followed by his pediatrician, who reassures the parents that the patient’s weight is tracking along a consistent trend. The parents, however, continue to be concerned about inadequate weight gain and so present to...