Final answer:
Infancy galactosemia usually manifests soon after birth once an infant is exposed to lactose from milk, due to the inability to process galactose properly because of an enzyme deficiency. It is treated with a lactose-free diet to avoid symptoms such as diarrhea and vomiting, and diagnosed with tests such as stool acidity testing in young infants.
Step-by-step explanation:
When does Galactosemia of Infancy Present?
Galactosemia typically presents in infancy, soon after a newborn begins consuming milk, which contains lactose that is broken down into galactose. Due to a deficiency of the enzyme galactose-1-phosphate uridyl transferase, infants with galactosemia are unable to adequately convert galactose into glucose leading to the accumulation of galactose in the blood, a condition known as galactosemia, and its excretion in the urine, known as galactosuria. This often results in symptoms such as diarrhea and vomiting when the infants are exposed to lactose.
It is essential to manage galactosemia with a lactose-free diet to prevent severe symptoms and long-term complications. Metabolism of galactose and its role in the synthesis of lactose in lactating mammary glands is significant for understanding how lactose-free milk substitutes can serve as a remedy for affected infants. Stool acidity tests may help diagnose lactose intolerance in small infants, where other forms of testing are risky or impractical.