Sepiapterin Reductase Deficiency: Molecular Analysis in a New Case Presenting with Neurotransmitter Deficiency without Hyperphenylalaninemia

A 27 year-old woman presenting with the clinical picture characterized by hypersomnolence, mild psychomotor retardation, dystonia, oculomotor apraxia, weakness, and striking diurnal variations of symptoms was found to be sepiapterin reductase (SR)-deficient by investigation s of pterins in cytokine stimulated fibroblasts. There was no detectable SR activity in the non-stimulated fibroblasts and mutation analysis revealed a homozygous Arg to Gly exchange at codon 150 (R150G). This is the third case found with SR deficiency characterized by a severe monoamine neurotransmitters deficiency without hyperphenylalaninemia.