Newborn screening for tyrosinemia type I: Further evidence that succinylacetone determination on blood spot is essential

Tyrosinemia type I is a genetic disorder characterized by accumulation in the blood and urine of the toxicmetabolite succinylacetone (SUAC), not detectable in healthy samples. In many countries, newborns are screened for tyrosinemia type I using tyrosine as a primary marker. Unfortunately, tyrosine accumulation may take longer to occur and it may be not obvious when specimens are collected, in the first few days of life, as for new born screening. In 2008, we reported changes to simultaneously measure acylcarnitines, amino acids, and SUAC duringexpanded newborn screening. We established the usefulness of this method after identifying a first asymptomatic new born affected by tyrosinemia type I. Now we report a second infant with positive SUAC screening result (14.1 mmol/L, n.v.