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Enhancing Newborn Screening for Tyrosinemia Type I

Wadsworth Center, New York State Department of Health, P.O. Box 509, Albany, NY

^aAddress correspondence to this author at: Wadsworth Center, New York State Department of Health, P.O. Box 509, Albany, NY 12201-0509, E-mail kpass@wadsworth.org

The first 20% of the full text of this article appears below.

Hepatorenal tyrosinemia, also known as tyrosinemia type I (Tyr-I) is an autosomal recessive inborn error of metabolism. The primary enzyme defect has been attributed to a deficiency of fumarylacetoacetase (EC 3.7.1.2)(1). Tyr-I is usually asymptomatic in newborns, but if left untreated it affects liver, kidney, bone, and peripheral nerves; in its most severe form, affected infants may die from liver failure in the first months of life(2). The majority of Tyr-I patients can be treated with 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) with promising outcomes(3)(4). The incidence of this condition is estimated to be 1:100 000 but may be much higher in certain populations such as the province of Quebec, where it occurs once in every 20 000 live births(5). Given the effectiveness of treatment and a test for its marker in the Guthrie specimen, Tyr-I fulfills the criteria for newborn screening and is included in the American College of Medical Genetics’ core panel of newborn screening recommendations(6).

Most newborn screening programs detect Tyr-I by measurement of tyrosine in Guthrie specimens (dried blood spot)(7)(8)(9). This method is convenient because tyrosine can be extracted and monitored along with other amino acids and acylcarnitines present in newborn screening panels(7)(8)(9). It has become clear, however, that tyrosine alone is an inadequate marker for screening of Tyr-I because tyrosine measurement lacks specificity and cannot distinguish Tyr-I from other disorders in tyrosine catabolism and transient hypertyrosinemia(10)(11). Even more disconcerting are reports . . . [Full Text of this Article]