Zahorsky1 in 1910, and again in 1913, described a symptom complex under the designation of "roseola infantum," which he believed deserved a nosologic position of its own.
His description of the condition is as follows:
"The patient is almost always a child under 3 years of age who suddenly becomes ill with high fever. The physician is called, and on examination finds nothing to account for the fever. The fever continues but no diagnosis can be made on the second, third or even fourth day. Then the temperature drops to normal, or nearly so, and the child, who has been drowsy and irritable, sits up and commences to play. Coincidentally with the decline in the temperature a morbilliform rash appears on the face and neck and rapidly spreads over the body. The eruption disappears in from twenty-four to forty-eight hours. There are no complications or sequels. No desquamation follows
PARK JH, MICHAEL JC. A PECULIAR ERUPTIVE DISEASE OCCURRING IN INFANCY. Am J Dis Child. 1922;23(6):521-526. doi:10.1001/archpedi.1922.01910420052009