Exanthems from an ancient family of five1,2
Achieved great fame; though now just four remain alive.
Rubella, Measles, Scarlet Fever are the three
First christened, since the fourth succumbed in infancy.
Yet little Fifth Disease cannot assume Fourth's name,
Just as the "junior" would not then the "senior" claim.
Instead, a new fourth member we might now adopt,
And for the orphan, Roseola, I would opt.
(Though it was called the Sixth disease by just a few,3 Procedures for adoption were not carried through.)
Or should the fourth become that diagnostic cache—
The MD's sage pronouncement, "It's a 'Viral Rash'..."?
HALL CB. The Exanthematous Family Tree—Diseases One, Two, Three, and Five?. Am J Dis Child. 1977;131(7):816. doi:10.1001/archpedi.1977.02120200096027