Neurotransmitters are chemical messengers tasked with the transmissions of signals from one nerve cell to another across the synaptic cleft. Congenital disorders of synthesis, transport, or degradation of neurotransmitters are rare metabolic disorders. Leading symptoms of a neurotransmitter disorder are muscle hypotonia, (progressive) psychomotor retardation, epilepsy, ocular symptoms, and extrapyramidal movement disorders. Among the most important neurotransmitters are the biogenic amines: dopamine, adrenaline, and noradrenaline, as well as serotonin. Tetrahydrobiopterin is an essential co-factor in the synthesis of biogenic amines. A number of defects in the metabolism of biogenic amines and pterins — the corresponding clinical manifestations include Segawa syndrome — can be elucidated by molecular genetics. The diagnosis of a defect in dopaminergic/serotonergic neurotransmission may be relevant to therapy: starting treatment early can have a significant effect on the prognosis.
Brennenstuhl et al. 2019, Neuroped 50:2 / Mercimek-Mahmutoglu et al. 2015, Orphanet J of Rare Dis 10:12 / Szymanska et al. 2014 In: Pokorski M. (eds) Neurotransmitter Interactions and Cognitive Function. Adv in Exp Med and Biol, vol 837. Springer, Cham