A 15-year-old with drop attacks and unsteadiness while descending stairs.

We describe a 15-year-old young man with mental retardation, epilepsy, drop attacks, and dystonic gait since early childhood. The intrauterine and perinatal course was unremarkable. The drop attacks were characterized by a sudden loss of lower-extremity tone without impairment of consciousness and were triggered by the process of dressing. He would consistently become unsteady while descending stairs. A neurologic evaluation during early childhood had been negative for various genetic and metabolic disorders. The drop attacks prompted a neurologic re-evaluation at age 15 years, subsequent to which a definitive diagnosis was established. We describe the clinical features of a degenerative disorder that manifests associated with down-gaze paresis, dystonia, and nonepileptic drop attacks in childhood. Disorders that can mimic this condition are also discussed.