Succinylacetone and succinylacetoacetate are responsible for the observed liver and kidney toxicity in patients with tyrosinemia type 1, rare pediatric disease causing progressive liver failure and liver cancer in young children. Tyrosinemia type I occurs due to a deficiency in fumarylacetoacetase (FAH), the final enzyme in the tyrosine catabolic pathway. In patients with tyrosinemia type I, catabolic intermediates maleylacetoacetate and fumarylacetoacetate are converted to the toxic metabolites succinylacetone and succinylacetoacetate. Succinylacetone can also inhibit the porphyrin synthesis pathway leading to the accumulation of 5-aminolevulinate, a neurotoxin responsible for the porphyric crises characteristic of tyrosinemia type I