Hypermethioninemia (MET) is a condition that occurs when there is a high amount of methionine in the body. This is a rare condition, and the number of people with it worldwide is currently unknown. Many people with MET do not show signs of the condition. However, if MET is untreated, it may cause learning delays, muscle weakness, and other health problems in some affected individuals. If an individual does show symptoms, they will appear within the first few weeks of life and may include developmental delays, muscle weakness, sleeping longer than usual, and a "cabbage-like" smell. Babies who receive treatment, which includes a special diet, typically have no health complications and may grow and develop normally. Babies who show signs of MET and do not receive treatment are at risk for intellectual disabilities. Many babies are screened to see if they may be affected by MET at birth, but the conditions included in newborn screening vary by state by state. For more information, visit Baby's First Test.