Background: The main objective of this prospective, multicenter study (REVEAL-CP) was to test children with cerebral palsy-like signs and symptoms for raised 3-O-methyldopa (3-OMD) blood levels, a biomarker for aromatic L-amino acid decarboxylase deficiency (AADCd). A secondary objective was to characterize the molecular basis for the defective aromatic L-amino acid decarboxylase (AADC) gene product.

Methods: Patients were identified in pediatric secondary and tertiary care hospitals through database searches and personal communication. 3-OMD concentrations from Guthrie card tests were determined using liquid chromatography/mass spectrometry. If 3-OMD was raised, cerebrospinal fluid analysis and dopa decarboxylase (DDC) gene sequencing were performed. An in-silico mutagenesis analysis was carried out to model altered AADC enzymes.

Results: In total, 166 patients were enrolled in this study. The median age was 8 years. Sixty-six patients (39.8%) had a diagnosis of cerebral palsy, with the most common type being "mixed" (n = 42; 25.3%). One patient (0.6%), an 11-month-old boy from Italy, was diagnosed with AADCd caused by a homozygous, pathogenic DDC variant (c.749C>T; p.Ser250Phe). Three-dimensional modeling of the Ser250Phe AADC enzyme variant revealed its destabilization.

Conclusions: A Guthrie card test for 3-OMD is a recognized screening technique for AADCd. If universal newborn screening for this metabolic disease is not available, children with signs and symptoms of a movement disorder should be investigated for AADCd.