In which condition would you expect to see a significant increase in branched-chain amino acids in the urine?

In the scenario presented, a significant increase in branched-chain amino acids in the urine is characteristic of Maple Syrup Urine Disease (MSUD). This metabolic disorder arises due to a deficiency in the branched-chain α-keto acid dehydrogenase complex, which is responsible for the catabolism of the branched-chain amino acids: leucine, isoleucine, and valine.

When there is a deficiency of this enzyme complex, the degradation of these amino acids is impaired, leading to their accumulation in the body. The excess branched-chain amino acids are then excreted in the urine, causing the distinctive sweet odor associated with the condition. The name "Maple Syrup Urine Disease" comes from this characteristic smell, reminiscent of maple syrup.

In contrast, the other conditions listed are related to different metabolic errors and do not involve the metabolism of branched-chain amino acids. For instance, homocystinuria is associated with the accumulation of homocysteine due to defects in its metabolism, phenylketonuria results from phenylalanine accumulation, and alkaptonuria involves the accumulation of homogentisic acid due to a deficiency in the enzyme homogentisate oxidase. Therefore,