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A nine-day-old boy was admitted to the pediatric ward of a regional hospital after a clinic appointment, where he was found to be jaundiced with a total serum bilirubin of 100 umol/L. He had been followed by the public health nurse in the community for poor weight gain in his first week of life. His weight on the day of admission was 2.52 kg, while his birth weight had been 2.81 kg. The pregnancy and family history were unremarkable, and the boy was born at term with an uncomplicated initial stay in the hospital. Breastfeeding had been established before discharge home on the second day of life and was supplemented with formula by bottle after an appointment on the fifth day at the clinic, where the boy was found to have lost over 10% of his birth weight. His parents reported that he was becoming less and less interested in eating, and by the day of admission, they needed to wake him to eat. On admission, he was jaundiced and moderately dehydrated but otherwise had a normal physical examination. Other than the hyperbilirubinemia, the remainder of the initial blood work was unremarkable. The direct antiglobulin test was negative. The baby was started on double phototherapy and intravenous rehydration, and within 6 hours, he had a repeat total bilirubin of 309 umol/L, with a direct bilirubin of s4 umol/L. A glucose meter check also performed at the time showed a reading of 26 mmol/L. A serum sample sent to the laboratory showed the glucose to be 2 mmol/L. Repeat glucose meter checks performed overnight were all greater than 20 mmol/L, while laboratory samples were in the low to normal range. After approximately 24 hours of phototherapy, the total bilirubin was 250 umol/L, with a direct bilirubin of 39 umol/L. The baby developed a bronzed color (direct hyperbilirubinemia), and liver function tests showed an alkaline phosphatase of 685 U/L, alanine aminotransferase of 83 U/L, and aspartate aminotransferase of 155 U/L. A urine test result was able to quickly point to the likely diagnosis. 1. What is the most likely diagnosis? 2. Explain your answer, and how you arrived at your conclusion. Include evidence from the case study. Explain the underlying biochemical mechanism(s) for this disorder.
3. What should be discussed about the nutritional requirements for the baby? 4. How long should the parents adhere to the special diet? 5. If galactosemia is not treated, what complications might occur?