Glutaric acidemia type 1: outcomes before and after expanded newborn screening

Abstract

Glutaric acidemia type 1 (GA-1) is an autosomal recessive disorder of lysine, hydroxylysine, and tryptophan metabolism. Patients may present with brain atrophy, macrocephaly, and acute dystonia secondary to striatal degeneration typically triggered by an infection, fever, and/or dehydration. This disorder is identified on expanded newborn screening by increased glutarylcarnitine. We evaluated the outcome of 19 patients with GA-1. Ten patients were diagnosed by newborn screening and 9 were diagnosed clinically. DNA testing in 12 patients identified 15 different mutations in the glutaryl-CoA dehydrogenase gene. Plasma glutarylcarnitine and urinary 3-hydroxyglutaric acid were elevated in all patients. However, only 10 of 17 patients who underwent urine organic acid analysis were high excretors of glutaric acid. Levels of glutarylcarnitine in plasma correlated with the urinary excretion of glutaric and 3-hydroxyglutaric acid, but not with clinical outcome. Plasma lysine was also significantly correlated with urinary glutaric acid, but not with urinary 3-hydroxyglutaric acid. Brain magnetic resonance imaging in all patients showed wide Sylvian fissures before treatment, which normalized by 4 years of age in treated patients. The occurrence of three adverse outcomes (oral motor function, ambulatory capability, and dystonic movements) was on average reduced by 75% (relative risk 0.25 to 0.28) in patients identified by newborn screening compared to patients diagnosed before newborn screening (Fisher's exact test; p=0.0055 for oral motor function and ambulatory capability; p=0.023 for dystonic movements). Newborn screening is effective in the prevention of complications in patients with GA-1 when coupled with treatment strategies.