Rheumatic fever is often associated with St. Vitus's Dance. Seven out of ten victims are girls. They are usually "nervous," "high-strung" children to begin with. The disease usually burns itself out in two, three months.
The most manifest symptom of St. Vitus's dance is continued involuntary action of the voluntary muscles, to a greater or lesser degree - the extent of the muscles affected, and the intensity of their affection, varying with the severity of the disease.
Origin
So named because a visit to St Vitus's shrine was believed to alleviate the disease.