Maleylacetoacetate isomerase deficiency

Deficiency of maleylacetoacetate isomerase (MAAID) is characterized by mild elevations in succinylacetone in blood and urine, usually identified by newborn screening. Liver function and coagulation are normal. MAAID is differentiated from hepatorenal tyrosinemia (TYRSN1; 276700), which is also identified by hypersuccinylacetonemia on newborn screening but is a severe disorder with hepatic failure, renal tubulopathy, rickets, and porphyria-like neurologic crises. MAAID and TYRSN1 are caused by mutations in genes encoding the penultimate and ultimate enzymes, respectively, in the phenylalanine and tyrosine degradation pathway (summary by Yang et al., 2017). [from OMIM]