Propionic aciduria and methylmalonic aciduria are inherited metabolic disorders that result in the accumulation of toxic metabolites and excessively high levels of ammonia.

Carglumic acid decreases ammonia levels and is a recognised treatment for acute hyperammonaemia in propionic aciduria and methylmalonic aciduria; however, there is limited experience with its long-term use. The PROTECT study is an ongoing observational study of the effects of long-term carglumic acid treatment in adults and children with propionic aciduria or methylmalonic aciduria.

The interim analysis reported in this article presents data from ten individuals in the PROTECT study. The data indicate that treatment with carglumic acid for at least 1 year reduces peak plasma ammonia levels and the frequency of metabolic decompensation events, as well as the duration of inpatient hospital stay due to metabolic decompensations in some patients.