Many diseases are identified with medical eponyms. Other have been called for centuries with a Saint's name, according to the catholic tradition, and some people might still recall a different nomenclature.
I found some time to google St. Vitus.
According to the Roman Catholic tradition, St. Vitus is one of the fourteen holy helpers - whose intercession is particularly effective in the cure of diseases.
St. Vitus, patron of actors, comedians, dancers, is venerated against chorea, hydrophobia, lethargy and epilepsy. He also confers protection against lightning strikes / stormy weather and animal attacks (no clue why).
A good hagiography (not angiography) can be found here. The website states
For obscure reasons, some 16th century Germans believed they could obtain a year’s good health by dancing before a statue of Saint Vitus on his feast day. This dancing developed almost into a mania, and was confused with chorea, the nervous condition later known as Saint Vitus’ Dance, the saint being invoked against it.
I have no clue if this is true or not. Emperor Diocletian called the young St. Vitus to help cure his son, who had Vitus' same age, from the demon - some say convulsions, but it might well be the Sydenham's chorea. Infact before Huntington's observations in 1872, Sydenham's chorea was maybe one of the very few causes of chorea known. It was a fairly common disease in young children/adults at those times, and I presume also in roman ones - and maybe it's really from St. Vitus' interecession with Diocletian's son that people have started to call it St. Vitus' dance!
Wow. Great medical history brainstorming.