DDC and hyperinsulinemic hypoglycemia, familial, 4: Further inherited neurotransmitter disorders associated with seizures are succinic semialdehyde dehydrogenase (SSADH) deficiency (GABA metabolism disorder), aromatic L-amino acid decarboxylase (AADC) deficiency (dopamine/serotonin synthesising enzyme disorder, seizures are described but uncommon) and the aforementioned non-ketotic hyperglycinemia (glycine metabolism disorder) (80, 153–156).