A five years old female presented with the typical clinical features of AADC deficiency. She was floppy, with no head control, had intermittent limb dystonia, and an upward deviation of the eyes (oculogyric crisis). This patient possessed compound heterozygous mutations in DDC (p.Trp105Cys, p.Pro129Ser), with a CSF draw indicating abnormal patterns of biogenic amine metabolites, compatible with AADC deficiency.
After her diagnosis at 3 years of age, medication with levodopa and vitamin B6 failed to show any efficacy. Subsequent administration with a MAO-B inhibitor improved her psychomotor functions to the extent that at 5 years of age she could walk several meters with support.
Our analyses of chemical findings, together with in silico structure predictions, lead us to hypothesize that this patient retained some AADC activity. In these cases, accurate diagnosis and early treatment should improve patient outcome.