Hot Topics in Metabolism

New developments for several inborn errors of metabolism disorders detected by newborn screen are explored—phenylketonuria, liver transplant for urea cycle disorders, maple syrup urine disease, methylmalonic acidemia/propionic acidemia, and galactosemia. Phenylketonuria advancements discussed include medical foods, low protein foods, large neutral amino acid therapy, Kuvan, and pegylated recombinant phenylalanine ammonia lyase. Clinical and quality of life outcomes of liver transplantations for urea cycle disorders and maple syrup urine disease are described. The recent developments and controversies of liver transplants in methylmalonic acidemia/propionic acidemia are explored. Lastly, feeding complications and dietary restrictions in galactosemia are reviewed.