Introduction: Glutaric Acidaemia type I (GA-I) is an autosomal recessive progressive neurodegenerative inborn error of metabolism caused by deficient activity of the enzyme glutaryl-CoA dehydrogenase (GCDH). In most cases, the diagnosis is established biochemically by the detection of glutaric acid and 3-hydroxy glutaric acid in urine and glutarylcarnitine in plasma. Patients excreting small amounts of glutaric acid may be overlooked.
Objective: To investigate the value of expanded newborn screening by adding the measurement of urine glutarylcarnitine to conventional chromatography-mass spectrometry (GC-MS) in the diagnosis of GA-1.
Material and methods: We report clinical and biochemical data in 5 GA-I patients diagnosed in our Hospital. Details regarding biochemical diagnosis are emphasised and the absence or presence of symptoms was correlated with neuroimaging findings, age at diagnosis and treatment.
Results: Two patients showed high glutarylcarnitine levels in plasma and were identified by routine newborn GC-MS screening. Following early appropriate treatment they are asymptomatic 6 years later. Two patients with delayed diagnosis displayed neurological sequels in spite of treatment. The remaining patient, who presented with encephalopathic episode at age 8 months showed normal glutarylcarnitine levels in routine plasma GC-MS but high urine glutarylcarnitine levels in a retrospectively screened urine sample from the newborn period.
Conclusions: Early treatment seems to positively influence the clinical evolution of GA-I patients. Thus, improving the identification of GA-I represents an important diagnostic challenge. The urinary excretion of glutarylcarnitine is a specific biochemical marker of GA-I and allows the identification of patients without glutaric aciduria and with normal plasma acylcarnitine profiles.