Tyrosinemia is a genetic disease that causes liver failure, cirrhosis and liver cancer. Succinylacetone is a substance that is elevated in tyrosinemia. Using succinylacetone for newborn screening permits early treatment of tyrosinemia, which can prevent liver disease. Six babies were detected by screening but had normal liver function. Even without special treatment, each child has maintained normal liver function. Each has a genetic deficiency of an enzyme called maleylacetoacetate isomerase, that is related to but different from the enzyme that causes tyrosinemia. Recognizing this newly-discovered condition is important for proper genetic counselling and treatment of babies detected by tyrosinemia screening. (By Dr. Grant Mitchell, http://jmg.bmj.com/content/early/2016/11/22/jmedgenet-2016-104289 )