Genome‐wide association studies highlighted PTPRD as a major susceptibility locus for restless‐legs syndrome and have since extended its reach to addiction, obsessive‐compulsive disorder, attention‐deficit/hyperactivity disorder, autism spectrum disorder, anxiety, and Alzheimer disease (see the “PTPRD mutations in brain disorders” section below for details). The gene discussed is PTPRD; the disease is early-onset autosomal dominant Alzheimer disease.