SLC6A3 and SLC6A3-related dopamine transporter deficiency syndrome: Classical DTDS presents in early infancy (14, 15); however, later studies have described cases with childhood/adolescent disease onset (16), and we recently identified an adult patient with compound heterozygote missense mutations in SLC6A3 that only partially disrupt DAT function; this patient has an atypical form of DTDS with adult-onset of motor symptoms and comorbid neuropsychiatric disease (17).