Is Succinyl Acetone a Common Metabolic Link Between Tyrosinemia and Alkaptonuria?

Succinylacetone is an abnormal metabolite found in Tyrosinemia -I (HT) due to the primary deficiency of fumaryl acetoacetate hydrolase. Interestingly this metabolite is not only specific to this autosomal recessive disease, but is also found in one of the rare and first discovered inherited disorder alkaptonuria. Though the metabolic pathway is same for both the disorders, the primary defects involved in both of these are distinct. Hence, this study suggests that presence of SA shouldn't be misdiagnosed for tyrosinemia. The objective of this study was to demonstrate the presence of SuccinylAcetone in alkaptonuria and tyrosinemia. Succinylacetone was assayed by spectrophotometry and the organic acid profile determined by TLC. Spectrophotometric assay showed the presence of succinylacetone by the inhibition of [delta]-aminolevulinate dehydratase (ALA-D) in both the disorders, but comparatively less in alkaptonuria positive samples. However qualitative measurement by TLC also showed the presence of SA spot, thereby confirming the presence of succinylacetone in alkaptonuria also. As the presence of succinylacetone was confirmed by the methods mentioned, we hereby conclude that succinylacetone isn't a specific marker for hereditary tyrosinemia--I as it can lead to misdiagnosis for the same, so alkaptonuria samples should be followed up and diagnosed suitably with consecutive specific panel of test.