We report the video-polysomnographic sleep characteristics of a 25-year-old woman with the Mulvihill-Smith syndrome, a rare clinical condition characterized by progeria-like aspect, peculiar multiple pigmented nevi, low stature, and cognitive impairment. Among the various exams, two overnight video-polysomnographic recordings were carried out; moreover, cerebral MRI and molecular analysis of the prion protein gene (PRNP) were also performed. The video-polysomnographic recordings showed the absence of clear sleep episodes but the presence of periods during which the patient had poor contact with the environment, stereotyped afinalistic movements of the upper limbs and hands, irregular or periodic breathing (with central apnea episodes), heart rate arrhythmia, and rapid eye movements. Cerebral MRI showed only diffuse mild enlargement of the cortical sulci and the molecular genetics analysis of the PRNP was normal. Our clinical and neurophysiological study seems to indicate that a particular condition of severe sleep disruption, similar to some extent to that reported in the fatal familial insomnia and in the Morvan fibrillary chorea, which has been indicated as Agrypnia Excitata in recent literature, might be associated with the Mulvihill-Smith syndrome. The inclusion of a detailed study on the sleep characteristics of eventual additional patients will certainly help our understanding of this rare condition.