OBJECTIVES: AADC deficiency is a rare neuro-metabolic disease associated with a range of symptoms and functional issues. The aim of this study was to assess the burden of AADC deficiency in a multi-country patient cohort in Europe.

METHODS: A case study questionnaire was developed based on information from literature and expert input including questions around patient characteristics, disease course, signs and symptoms and motor milestone achievement. Physicians experienced in the management of patients with AADC deficiency were asked to complete the questionnaire based on the information available in medical records and their knowledge of their patient(s).

RESULTS: Overall, ten interviews with clinicians in France, Italy and Spain were conducted providing information on 20 individuals with AADC deficiency aged 3-40 years (10 were able to stand/walk with assistance, 2 able to sit, and 8 had no motor function/head control). Diagnosis of AADC deficiency occurred less than 2 years after the initial onset of symptoms for 12 of 20 patients (60%); however there were ≥19 years between symptom onset and diagnosis for 4 of 20 patients (20%). The most common mutation was c.1543C>T (p.Ser250Phe). The median (IQR) duration of follow-up per patient at the time of survey was 5.00 (2.00-7.50) years. Patients with AADC deficiency were experiencing a wide range of symptoms: all patients (100%) were experiencing movement disorders; 18 (90%) developmental delay (motor, cognition and/or speech), 17 (85%) sleeping problems and 16 (80%) gastrointestinal problems. Other reported symptoms included insomnia (n=17 [85%]), dyskinesia (n=15 [75%]), oculogyric crisis (n=14 [70%]), dystonia (n=13 [65%]), hypotonia (n=12 [60%]), fatiguability (n=12 [60%]) and excessive drooling (n=12 [60%]).

CONCLUSIONS: This study shows the high burden of AADC deficiency as described by the signs and symptoms experienced by patients with this disease.