[5] In about half of cases, the signs and symptoms of this disorder become apparent within a few days after birth and include poor feeding, vomiting, seizures, and lack of energy that can progress to coma.

[citation needed] The enzyme encoded by IVD, isovaleric acid-CoA dehydrogenase (EC 1.3.99.10), plays an essential role in breaking down proteins from the diet.

If a mutation in the IVD gene reduces or eliminates the activity of this enzyme, the body is unable to break down leucine properly.

As a result, isovaleric acid and related compounds build up to toxic levels, damaging the brain and nervous system.

[citation needed] The urine of newborns can be screened for isovaleric acidemia using mass spectrometry,[3] allowing for early diagnosis.