Succinylacetone, Blood Spot
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Tyrosinemia type 1 (Tyr 1) is an autosomal recessive condition caused by fumarylacetoacetate hydrolase (FAH) deficiency. The incidence of Tyr 1 is approximately 1 in 100,000 live births, resulting in 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. Over the past decade, treatment with 2-(2-nitro-4-tri-fluoromethylbenzoyl)-1,3 cyclohexanedione (NTBC) became available and is particularly effective when initiated in newborns.
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.
Second-tier newborn screening for tyrosinemia type 1 in blood spots with nonspecific elevations of tyrosine
Diagnosis of tyrosinemia type 1
Follow-up of patients with tyrosinemia type 1
Normal: <5.0 mcM.
Elevations of succinylacetone (SUAC) above the reference range are indicative of Tyr I.
Patients with Tyr I who are treated with diet and/or NTBC (nitisinone) should have declining or normal values of SUAC.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Normal levels may be seen in affected individuals undergoing treatment.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
An interpretive report will be provided.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
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