All states in the US screen for MSUD through newborn screening programs. Newborns should be tested 1-3 days after birth with results reported within 24 hours, as early diagnosis and treatment (within the first 10 days of life) reduces the risk of permanent damage and allows for normal development. In countries that do not screen for MSUD in the neonatal period, children with MSUD may become severely handicapped or die before they are diagnosed.

Variant MSUD may be missed during newborn screening. Any child at risk or suspected of having MSUD should be tested promptly with a plasma amino acid panel and treated immediately if the results are positive or suspect.



Treatment of children with MSUD, which must be started as soon as possible, centers around a carefully controlled diet, the mainstay of which is a “medical food” or formula. The formula provides all essential nutrients except the 3 branched chain amino acids for which there is impaired metabolism: leucine, isoleucine, and valine. These are added to the diet as prescribed by the treatment team based on regular monitoring of growth and blood amino acid levels.

Food sources of protein are highly restricted. This regimen provides the child with adequate amino acids for growth and development while preventing high blood levels and symptoms.  Careful monitoring of protein intake and close medical supervision is required for life. Illness and stress, along with consuming too much protein from food, can raise the levels of amino acids and their toxic breakdown products (keto acids) in the blood. Even a mild illness can become life-threatening if it prevents adequate intake of food and formula. Dietary modification and, at times, hospitalizations are needed during these times. Tests are available to monitor the levels of amino acids and their keto acid derivatives in the blood and urine.

Liver transplant is an optional treatment for MSUD as a donor liver has enough enzyme activity to allow the person to live free of most of the effects of the disease. After transplant, the person with MSUD still carries the gene for the disorder and will pass it on to their offspring. But, in most instances, they are no longer in danger of a metabolic crisis and can eat a normal diet. It is important to note that elevated branched chain amino acid levels have been observed in some transplanted individuals during illness.