Clinical and neurocognitive outcome in symptomatic isovaleric acidemia

Retrospective data on 21 children and adults with symptomatic IVA diagnosed from 1976 to 1999 were analyzed for outcome determinants including age at diagnosis and number of catabolic episodes. Sixteen of 21 patients were evaluated cross-sectionally focusing on the neurological and neurocognitive status. Additionally, 155 cases of patients with IVA published in the international literature were reviewed and analyzed for outcome parameters including mortality.57% of study patients (12/21) were diagnosed within the first weeks of life and 43% (9/21) in childhood. An acute metabolic attack was the main cause of diagnostic work-up. 44% of investigated study patients (7/16) showed mild motor dysfunction and only 19% (3/16) had cognitive deficits. No other organ complications were found. The patients' intelligence quotient was not related to the number of catabolic episodes but was inversely related to age at diagnosis. In published cases, mortality was high (33%) if associated with neonatal diagnosis, following manifestation at an average age of 7 days.Within the group of "classical" organic acidurias, IVA appears to be exceptional considering its milder neuropathologic implications. The potential to avoid neonatal mortality and to improve neurologic and cognitive outcome under early treatment reinforces IVA to be qualified for newborn screening.Isovaleric acidemia (IVA) is known as one of the "classical" organic acidemias/acidurias. It is caused by a genetic deficiency of isovaleryl-CoA dehydrogenase (IVD) catalyzing the third step in leucine catabolism. The enzyme defect results in the accumulation of derivatives of isovaleryl-CoA including free isovaleric acid, 3-hydroxyisovaleric acid, isovaleryl (C5)-carnitine, and isovalerylglycine (IVG) which partly may exert neurotoxicity.The clinical presentation of IVA appears to be highly variable ranging from severely affected to asymptomatic subjects [1]. It may present either in the neonatal period as an acute episode of fu