text: what particular type of person can be affected by maple syrup urine disease?   maple syrup urine disease (msud) is an inherited metabolic disorder, that, if untreated, causes mental retardation, physical disabilities and death.  first described as a disease in 1954, it is a rare disorder, believed to be in all ethnic groups worldwide.  the national incidence is 1 in 225,000 births.    msud derives its name from the sweet, burnt sugar, or maple syrup smell of the urine.  the disorder affects the way the body metabolizes (processes) certain components of protein.  amino acids accumulate in the blood causing a toxic effect that interferes with brain functions.  the symptoms of classic msud are usually evident within the first week of life. the first symptoms in an infant are poor appetite, irritability, and the characteristic odor of the urine.  within days they lose their sucking reflex and grow listless, have a high-pitched cry, and become limp with episodes of rigidity.  without diagnosis and treatment, symptoms progress rapidly to seizures, coma, and death.  in some variant types, failure to thrive may be the first sign.  the earlier these children are diagnosed and treated, the less risk of permanent damage.  treatment of children with msud must be started as soon as possible, preferably at birth.  it involves a complex approach of maintaining metabolic control.  a special, carefully controlled diet is the focus of daily treatment.  this requires careful monitoring of protein intake and close medical supervision.  the diet centers around a synthetic formula  or "medical food" which  provides nutrients and all the amino acids except leucine, isoleucine and valine.  these three amino acids are added to the diet with carefully controlled amounts of food  to provide the protein necessary for normal growth and development without exceeding the level of tolerance.   various tests are available to monitor the levels of the amino acids and their keto acid derivatives in the blood and urine.  illnesses and stress, as well as consuming too much protein, raise these levels.  even mild illnesses can become life‑threatening.  a metabolic imbalance requires dietary changes and at times hospitalization.