A 4-week-old boy is brought to the pediatrician by his parents for an initial evaluation. His parents are concerned that he is not feeding well and has lost weight over the last 2 weeks. He was born at home via spontaneous vaginal delivery at 37 weeks of gestation to a G1P1 mother. His mother did not receive prenatal care. His blood pressure is 70/44 mmHg, pulse is 151/min, and respirations are 41/min. His weight is 3 kg (4th percentile) compared with 3.5 kg at birth (45th percentile). On physical exam, he is jaundiced with an enlarged liver and spleen. He does not appear to respond to visual stimuli, and further examination reveals bilateral clouding of the lens. Which of the following interventions could have avoided this patient's symptoms?
Vitamin B6 supplementation
Changing to a soy based formula
Providing imiglucerase enzyme replacement
Removing phenylalanine from maternal diet during pregnancy
Changing to a soy based formula
This patient who presents with failure to thrive, hepatosplenomegaly, and bilateral cataracts most likely has classic galactosemia. Patients with this disorder should avoid lactose-containing products by changing to a soy-based formula.

Classic galactosemia is an autosomal recessive defect in galactose-1-phosphate uridyltransferase. This enzyme is involved in the conversion of galactose to glucose, and a deficiency of this enzyme results in the accumulation of galactose 1-phosphate in the liver, kidney, and brain. This metabolite acts as a phosphate sink, meaning that it traps all free phosphate in the cytosol and inhibits the formation of other phosphate-dependent metabolites such as adenosine triphosphate. This results in failure to thrive, vomiting, lethargy, and hepatosplenomegaly after ingestion of galactose-containing products such as milk. Patients will also develop bilateral cataracts if the deficit is not detected in the first few weeks after birth. Avoiding galactose by changing to a soy-based formula will avoid the complications of this disorder.

Turck discusses using soy protein for infant feeding. The author notes that there are safety concerns with regards to the high phyto-estrogenic isoflavone content of these formulas. The author recommends that despite these safety concerns, these formulas should still be used in patients with classic galactosemia.

Incorrect Answers:
Answer A: Avoiding fruit juice and sweetened foods would be effective in the treatment of hereditary fructose intolerance. This disease presents similarly to classic galactosemia, but cataracts would not be seen in patients with this disease.

Answer C: Providing imiglucerase enzyme replacement would be effective in the treatment of patients with Gaucher disease, which can also present with failure to thrive. However, associated findings in this disease would be anemia and avascular necrosis of the bones.

Answer D: Removing phenylalanine from the maternal diet during pregnancy would be effective in the treatment of patients with phenylketonuria, which can also present with failure to thrive. However, these patients classically present with a "musty smell" and eczema.

Answer E: Vitamin B6 supplementation may be effective in mitigating the negative symptoms of homocystinuria. This disease may also present with cataracts or lens dislocations. Associated findings in this disorder would be marfanoid appearance and arachnodactyly.

Bullet Summary:
Patients with classic galactosemia should not be breastfed and should receive a galactose-free and lactose-free diet such as soy-based formulas.