What laboratory finding is indicative of Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD)?

In the context of Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD), the presence of C6 acylcarnitine in laboratory findings is a hallmark indicator of the condition. MCADD is an autosomal recessive disorder affecting the fatty acid oxidation pathway, specifically in the breakdown of medium-chain fatty acids. When MCADD is present, the body is unable to effectively metabolize these medium-chain fatty acids, leading to their accumulation.

C6 acylcarnitine, which is a product of incomplete fatty acid metabolism, signifies that the enzyme responsible for the oxidation of medium-chain fatty acids is not functioning adequately. The accumulation of these intermediates, including C6 acylcarnitine, can be detected in plasma during metabolic screening and is crucial for diagnosing MCADD.

Other laboratory findings mentioned, such as high plasma ammonia or elevated methylcitrate, may indicate different metabolic disorders, such as urea cycle disorders or certain organic acidemias, and are less specific for MCADD. The presence of high ketones could be a result of a fatty acid oxidation disorder but is not a definitive marker for MCADD specifically like the presence of C6 acylcarnitine.