Aromatic L-amino acid decarboxylase (AADC) deficiency (OMIM 608643) is a rare autosomal recessive neurodevelopmental disorder caused by biallelic loss-of-function pathogenic variants in DDC (HGNC:2719).1 AADC catalyzes an intermediate step in the synthesis of multiple neurotransmitters.2 Deficiency of this enzyme results in decreased synthesis of dopamine, serotonin, norepinephrine, and epinephrine. Clinical presentation typically consists of nonspecific findings in early infancy, including hypotonia, developmental delay, and feeding difficulties.