Diagnostic Approach for Neonatal Jaundice and Hepatomegaly

Immediate Diagnostic Considerations

The American Academy of Pediatrics and Genetics in Medicine recommend immediate measurement of plasma amino acids, urine succinylacetone, alpha-fetoprotein (AFP), and comprehensive metabolic workup to guide urgent treatment decisions for a 20-day-old neonate with severe jaundice, hypernatremic dehydration, seizures, and hepatomegaly 1, 2
Elevated blood or urine succinylacetone is diagnostic for tyrosinemia type 1 (HT-1), and AFP is almost always elevated in early infancy, often 10-fold higher than normal neonatal values 1, 2
The Society for Inherited Metabolic Disorders suggests that hepatomegaly, hypoglycemia, direct hyperbilirubinemia, elevated transaminases, and hypoalbuminemia may not all be present initially in HT-1, but coagulopathy can be an early sign 1, 2

The American College of Medical Genetics recommends plasma amino acids with specific attention to tyrosine and phenylalanine levels, urine succinylacetone, serum alpha-fetoprotein (AFP), and comprehensive metabolic panel including liver function tests 1, 2
Blood ammonia level should be monitored, with normal levels being less than 35 µmol/L in term infants, and levels greater than 50 µmol/L being abnormal 4
Abdominal ultrasound should be performed to evaluate hepatomegaly, assess liver architecture, and rule out structural abnormalities, and head ultrasound or MRI should be considered to evaluate for intracranial hemorrhage, cerebral edema, or structural brain abnormalities given seizure history 1, 2, 5

The European Society for Pediatric Gastroenterology, Hepatology and Nutrition recommends starting NTBC (nitisinone) immediately at 1 mg/kg/day divided into two doses, and initiating a low-protein diet with tyrosine and phenylalanine restriction for confirmed or highly suspected HT-1 1, 2
The Society for Inherited Metabolic Disorders suggests monitoring plasma tyrosine and phenylalanine levels, and verifying that succinylacetone becomes undetectable with NTBC therapy 1, 2
The American Academy of Pediatrics recommends correcting coagulopathy with fresh frozen plasma and vitamin K, treating hypoglycemia with IV dextrose, and continuing slow correction of hypernatremia for supportive care 1, 2