Symptoms and impacts of aromatic l-amino acid decarboxylase (AADC) deficiency among individuals with different levels of motor function

BACKGROUND: Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare neurological disorder associated with a range of symptoms and functional impairments. The aim of this study was to describe the experience of AADC deficiency across five different motor milestone health states. METHODS: Qualitative interviews were conducted with caregivers of individuals with AADC deficiency in Italy, Spain, Portugal and the United States. An interview guide was developed with input from clinical experts and caregivers, and explored the symptoms and impacts of AADC deficiency. Interviews were conducted by telephone and were recorded and transcribed. Data were analysed using thematic analysis and the symptoms and impacts were compared across health states. RESULTS: Fourteen caregivers took part, who provided care to 13 individuals with AADC deficiency aged 1–15 years. Six individuals were in the ‘no motor function’ health state, one in the ‘sitting unsupported’ health state, one in the ‘standing/stepping when fully supported’ health state and five in the ‘walking with minimal support’ health state. The results highlight a substantial impact of AADC deficiency, even among those who were able to walk with minimal support. Overall, those with better motor function also had better functional hand use, communication skills, ability to eat and perform other activities independently, and interact with their peers. The burden of caring was high across all health states, but caregivers of individuals in the walking health state were better able to participate in social and leisure activities. CONCLUSION: Individuals with higher levels of motor function had less severe symptoms and were better able to perform their daily, leisure and social activities. Treatments which improve motor function have the potential to improve other aspects of the lives of individuals with AADC deficiency and their caregivers.