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Maple syrup urine disease (MSUD) is a disorder of amino acid metabolism. Affected individuals can have repeated episodes of vomiting, lethargy, and encephalopathy. The disorder is named for the characteristic smell of burnt sugar or maple syrup in the urine and tissues. Disposable diapers and diaper creams are also known to cause a maple syrup odor in normal individuals. Typically, individuals with MSUD have elevated leucine, isoleucine, valine and alloleucine in their blood in a specific ratio. MSUD affects approximately 1:300 000 individuals and is detected as part of the Washington State newborn screening program.