DDC and aromatic L-amino acid decarboxylase deficiency: The DDC gene is associated with maintaining adequate levels of monoamine neurotransmitters and the production of AADC [22,23]. There are homozygous mutations that lead to loss of function in the DDC gene, thereby depleting the pools of the decarboxylase and causing a person to develop a fatal form of infantile Parkinsonism, known as AADC deficiency [22].