LAUSR

Dopamine transporter deficiency syndrome (DTDS) is a rare genetic disorder caused by variants of the SLC6A3 gene encoding the human dopamine transporter (DAT). The disease has 2 phenotypes: classic and atypical DTDS. Classic DTDS usually begins during early infancy with 1 or more nonspecific symptoms (eg, irritability and difficulty in feeding), axial hypotonia, hyperkinetic movement disorders (chorea, ballismus, dystonia, and orolingual dyskinesia), and oculomotor abnormalities (eg, recurrent oculogyric crises, saccade initiation failure, ocular flutter, and eyelid myoclonus). Over the course of years, affected individuals typically develop severe dystonia-parkinsonism, often further complicated by the persistence of additional movement disorders and oculomotor abnormalities. Patients with the atypical variant attain normal developmental milestones during infancy and early childhood. However, behavioral symptoms, such as those encountered in attention deficit hyperactivity disorder (ADHD), and a variety of movement disorders, including resting and action tremor, dysarthria, and dystonia, may develop over time during late childhood, adolescence, or adulthood. In this article, we describe a young boy with a classic presentation of DTDS because of a novel mutation in the SLC6A3 gene and discuss clinical and laboratory findings.