Prominent examples include recessive mutations in the dopamine transporter (SLC6A3) that give rise to a syndrome of infantile dystonia and parkinsonism (5, –, 7), dominant mutations in the norepinephrine transporter (SLC6A2) that cause familial postural hypotension (8), and mutations in glycine transporter 2 (SLC6A5) that result in hyperekplexia/startle disease (9, –, 11). Here, SLC6A2 is linked to Parkinson disease.