Chorea is an abnormal involuntary movement disorder, one of a group of neurological disorders called dyskinesias. The term chorea is derived from the Greek word for dance, as the quick movements of the feet or hands are comparable to dancing.
Sydenham's chorea or chorea minor (historically referred to as Saint Vitus Dance) is a disorder characterized by rapid, uncoordinated jerking movements primarily affecting the face, hands and feet.
In video 1, the patient shows rapid, irregular, involuntary movements of the limbs, neck, and trunk While lying in bed. In video 2, jerking movements and gait disturbance can be seen as the patient walks.
The patient was diagnosed with Sydenham's chorea, associated with group A streptococcus infection. Penicillin and tiapride were administered, and there was a slight reduction in choreic movements. The patient's symptoms completely resolved within 1 month after presentation.
See the related NEJM article: http://www.nejm.org/doi/full/10.1056/NEJMicm1303705
The mysterious dancing epidemic of 1518: Seldom pausing to eat or drink, many died from exhaustion
This article from PubMed describes the chorea epidemic:
In 1518, one of the strangest epidemics in recorded history struck the city of Strasbourg. Hundreds of people were seized by an irresistible urge to dance, hop and leap into the air.
In houses, halls and public spaces, as fear paralyzed the city and the members of the elite despaired, the dancing continued with mindless intensity. Seldom pausing to eat, drink or rest, 400 of them danced for days or even weeks. And before long, the chronicles agree, dozens were dying from exhaustion.
In a spin: the mysterious dancing epidemic of 1518. Waller JC. Endeavour. 2008 Sep;32(3):117-21. Epub 2008 Jul 7.