• Intermittent, rhythmical myoclonus that had been present in the lower limbs of a 68-year-old man for more than 50 years was obviously increased in frequency during the period when the patients suffered from acute transverse myelitis. The same type of movements were readily induced by irrigation of the urinary bladder during the period of paraparesis. Removal of some possible inhibitory influences from a myoclonic focus in the lower spinal cord with resulting heightened excitability was thought to be the mechanism of these phenomena, although direct irritation of the myoclonic focus by the inflammatory process was also conceivable. The patient had keratosis palmoplantaris hereditaria and retinal pigment degeneration, suggesting the possibility of a congenital neuroectodermal dysplasia.