|Values are valid only on day of printing.|
Second-tier newborn screening for tyrosinemia type 1 (Tyr 1) in blood spots with nonspecific elevations of tyrosine
Diagnosis of Tyr 1
Follow-up of patients with Tyr 1
Tyrosinemia type 1 (Tyr 1) is an autosomal recessive condition caused by fumarylacetoacetate hydrolase (FAH) deficiency. Tyr 1 can cause severe liver disease, hypophosphatemic rickets, renal tubular dysfunction, and neurologic crises. If left untreated, most patients die of liver failure in the first years of life. Treatment with 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3 cyclohexanedione is available and is particularly effective when initiated in newborns. The incidence of Tyr 1 is approximately 1 in 100,000 live births.
While tyrosine can be determined by routine newborn screening, it is not a specific marker for Tyr I and often may be associated with common and benign transient tyrosinemia of the newborn. Succinylacetone (SUAC) is a specific marker for Tyr I, but is not detectable by routine newborn screening. This assay determines SUAC in newborn blood spots by tandem mass spectrometry. Additional follow-up testing may include confirmatory molecular analysis of the FAH gene.
An interpretive report will be provided.
Normal: <5.0 mcM
Elevations of succinylacetone (SUAC) above the reference range are indicative of tyrosinemia type 1 (Tyr 1).
Patients with Tyr I who are treated with diet and/or 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3 cyclohexanedione (nitisinone) should have declining or normal values of SUAC.
Normal levels may be seen in affected individuals undergoing treatment.
1. Larochelle J, Alvarez F, Bussieres JF, et al: Effects of nitisinone (NTBC) treatment on the clinical course of hepatorenal tyrosinemia in Quebec. Mol Genet Metab 2012;107(1-2):49-54
2. Mitchell GA, Grompe M, Lambert M, Tanguay RM: Hypertyrosinemia. In The Metabolic and Molecular Bases of Inherited Disease. Eighth edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. New York, McGraw-Hill Book Company, 2001, pp 1777-1805