Maple syrup urine disease: Favourable effect of early diagnosis by newborn screening on the neonatal course of the disease

BACKGROUND: In the rare autosomal recessive disorder maple syrup urine disease (MSUD) the accumulation of the branched-chain amino acids and their metabolic products results in acute and chronic brain dysfunction. Since 2002, MSUD has been part of the extended newborn screening programme in Germany and Austria. Early diagnosis and intervention during the presymptomatic or early symptomatic period should improve the outcome of the patients, which would make the case for screening for MSUD. AIM: The aim of the study was to evaluate the clinical course and alterations of marker metabolites during the first weeks of life in 10 patients with classical MSUD detected by newborn screening (NBS) in comparison with the 10 youngest German patients diagnosed clinically. METHOD: Laboratory data as well as information on clinical course and management during the neonatal period were obtained retrospectively. RESULTS: Patients detected in NBS presented with lower plasma leucine concentrations at confirmation of diagnosis and less severe clinical symptoms. Lowering of leucine to below a critical threshold of 1000 micromol/L was achieved earlier than in patients diagnosed on clinical grounds. CONCLUSION: After diagnosis in screening, treatment can be initiated before the occurrence of severe metabolic decompensation. However, a favourable effect can only be achieved with immediate transfer of the neonate to a metabolic centre for adequate treatment in case of a positive screening result.