Orthostatic tremor in monozygotic twins

Orthostatic tremor (OT) is characterized by a feeling of unsteadiness during stance that disappears when sitting or lying, associated with a fine-amplitude leg rippling while standing. Surface electromyography (EMG) recordings show a characteristic 13- to 18-Hz tremor.1 Tremor intensity is slowly progressive, sometimes spreading to other body regions, whereas the interval between standing and tremor triggering decreases over time. OT etiology remains unknown. Although most described cases of OT are sporadic, this disorder could be genetic, as suggested by few familial cases2–6 (see table E-1 on the Neurology Web site; go to www.neurology.org). We report two monozygotic twins with OT. The patients were two male monozygotic twins. Parents were not consanguineous, came from different villages, and remained healthy until their deaths (ages 76 and 87). Family history was negative for tremor or other neurologic disorders. The patients grew up together, lived in the same village, and worked as farmers until age 55, using agriculture chemical products. At age 68, in our outpatient clinic, they had tremor of both legs, occurring when standing and relieved …