Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare, autosomal recessive neurometabolic disorder, with an estimated prevalence of between 1:64,000 and 1:90,000 births in the USA, 1:116,000 in the European Union, 1:162,000 in Japan and 1:32,000 in Taiwan [1–3]. Here, DDC is linked to hyperinsulinemic hypoglycemia, familial, 4.