Treatable and preventable causes of inborn errors of metabolism: Cohort of neurotransmitter disorders in children from India

Background

Neurotransmitter disorders are a group of heterogeneous conditions that comprise defects in synthesis, transport, receptor binding, and degradation of neurochemical messengers. These rare disorders range from mild intermittent dystonia to lethal encephalopathies. The natural history and clinical presentation remain far from established.

Objectives

The study was conducted between October 2015 and September 2024. This study aims to describe the spectrum of clinical presentation, laboratory, imaging features, and genetic profiles of children diagnosed with neurotransmitter disorders and to assess the treatment modalities and clinical outcomes in these children.

Results

Among 29 patients, the median age was 12 months, with a male predominance. Positive family history was noted in 9 cases. The most frequent presentation was global developmental delay (GDD), dystonia, and seizures with autonomic disturbances, with diurnal variation. Various subcategories of neurotransmitter disorders are aromatic L amino acid decarboxylase deficiency-7 cases, tyrosine hydroxylase deficiency-3 cases, dopamine transporter deficiency syndrome-1 case, vesicular monoamine transporter 2 deficiency (VMAT2)-2 cases, GTP cyclohydrolase type deficiency-1 case, 6-pyruvoyl-tetrahydropterin synthase deficiency-1 case, dihydropteridine reductase deficiency-3, sepiapterin reductase deficiency-1 case, glycine encephalopathy-1 case, FOLR1-related cerebral folate transport deficiency-3 cases, and succinic semialdehyde dehydrogenase deficiency-5 cases. Metabolic workups were normal in all cases, with elevated phenylalanine levels in tandem mass spectrometry (TMS) in 5 children. Neuroimaging and electroencephalogram (EEG) were abnormal in 7 and 5 children, respectively. Multi-pronged and early treatment ensured better outcomes in these children.

Conclusion

The most common type of neurotransmitter disorder in our series was aromatic L-amino acid decarboxylase deficiency, with the most common presentation being global developmental delay and dystonia.