A review of aromatic l-amino acid decarboxylase (AADC) deficiency in Taiwan

Aromatic l-amino acid decarboxylase deficiency (AADCD) is a rare inherited disease prevalent in South East Asia. This disease is due to the founder mutation IVS 6 + 4A > T (c.714 + 4A > T), which accounts for most alleles. Patients with this mutation have severe phenotypes. About 90 % of these patients in South East Asia do not have head control and cannot sit, stand, or speak from birth to the time of observation. In 2012, a gene study to treat these patients with intraputamen injection of adeno-associated virus2-human AADC showed prominent motor improvement and an increased PDMS-2 score 12 months after treatment. In addition, systemic gene therapy in a mouse model of AADCD achieved widespread correction of the Ddc gene. In this article, we review the natural history, clinical course, and treatment effects seen in these clinical and mouse studies. Future studies focusing on noninvasive viral vector delivery or alternative emerging treatments may also benefit patients with AADCD.