Disorders of monoamine metabolism: inherited disorders frequently misdiagnosed as epilepsy

Pediatric neurotransmitter diseases are new emerging neurological diseases in children. They include tyrosine hydroxylase (TH) deficiency, aromatic L-amino acid decarboxylase (AADC) deficiency, succinic semialdehyde dehydrogenase (SSADH) deficiency, gua-nosine triphosphate cyclohydrolase I deficiency, sepiapterin reductase (SR) deficiency and cerebral folate deficiency. Of these, monoamine biosynthesis and metabolism disorders are one group of inherited disorders usually requiring specific diagnostic procedures. Children with disorders of neurotransmitters often present with psychomotor retardation, hypotonia and microcephaly. Although seizures may be more common in patients with SR deficiency, patients with TH or AADC deficiency only occasionally have non-epileptic myoclonus. However, the episodic dystonia and oculogyric crisis manifested in these patients are frequently misdiagnosed as epilepsy, and multiple anti-epileptic drugs (AEDs) may be given. In the present short review, the pathogenesis and diagnosis of these neurotransmitter disorders are discussed, with the hope that correct diagnosis of pediatric neurotransmitter diseases can reduce the unnecessary AED treatment.