Maple syrup urine disease (MSUD) is a rare but serious inherited condition.

It means the body can't process certain amino acids (the "building blocks" of protein), causing a harmful build-up of substances in the blood and urine.

Normally, our bodies break down protein foodssuch asmeat and fish into amino acids. Any amino acids that aren't needed are usually broken down and removed from the body.

Babies with MSUD are unable to break down the amino acids leucine, isoleucine and valine. Very high levels of these amino acids are harmful.

One of thecharacteristic symptoms of MSUD is sweet-smelling urine, which gives the condition its name.

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Medically Reviewed by a doctor on 28 Nov 2016