The Spectrum of Early Movement Disorders in Congenital Defects of Biogenic Amine Metabolism

This article analyzes the pattern of movement disorders in children with primary defects of biogenic amine metabolism emerging during the first 3 year of life. A PubMed search was performed using the keywords monoamine neurotransmitter disorders, congenital defects of biogenic amine metabolism, early onset movement disorders, autosomal dominant guanosine-triphosphate-cyclohydrolase deficiency, autosomal recessive guanosine-tryphosphate-cyclohydrolase deficiency, 6-pyruvoyl-tethrahydropterin synthase deficiency, sepiapterin reductase deficiency, dihydropteridine reductase deficiency, tyrosine hydroxilase deficiency, aromatic l-amino acid decarboxylase deficiency, dopamine transporter deficiency, and vesicular monoamine transporter 2. A personal series of 27 patients affected by these disorders was presented and discussed. Primary defects of biogenic amine metabolism result in a spectrum of movement disorders associated with derangement of postural reaction and global development delay. Movement disorders virtually represent the presentation symptoms in most of these diseases. The prominent early clinical patterns of movement disorders are akinesia (with rigidity or hypotonia) and hyperkinesia (dystonia, myoclonic jerks, and tremor). While some diseases present with a rather stereotyped clinical pattern (i.e.; Aromatic l-amino acid decarboxylase, sepiapterin reductase, and Dopamine transporter deficiencies), others (i.e.; Guanosine-triphosphate-cyclohydrolase, 6-pyruvoyl tetrahydropterin synthase, dihydropteridine reductase, and tyrosine hydroxylase deficiencies) may present with more pleomorphic features. As a general rule, earlier the onset of the disease is, more severe and generalized is the derangement of motor functions. Inherited disorders of monoamine neurotransmitter metabolism include the few idiopathic movement disorders with the possibility of etiological treatments. For these reasons, they should always be considered in the diagnostic work-up of children with early onset movement disorders.