Koplik's spots
Koplik spots (also Koplik's sign) are a prodromic viral enanthem of measles manifesting two to three days before the measles rash itself. They are characterized as clustered, white lesions on the buccal mucosa (opposite the upper 1st & 2nd molars) and are pathognomonic for measles. The textbook description of Koplik spots is ulcerated mucosal lesions marked by necrosis, neutrophilic exudate, and neovascularization. They are described as appearing like "grains of salt on a wet background", and often fade as the maculopapular rash develops. As well as their diagnostic significance they are important in the control of outbreaks. Their appearance, in contacts of a diagnosed case, before they reach maximum infectivity, permits isolation of the contacts and greatly aids control of this highly infectious disease.
Nobel laureate John F. Enders and Thomas Peebles, who first isolated measles virus were careful to collect their samples from patients showing Koplik's spots.
History
Koplik's spots are named after Henry Koplik (1858-1927), an American pediatrician who published a short description of them 1896, emphasising their appearance before the skin rash and their value in the differential diagnosis of diseases with which measles might be mistaken. He published two further papers on the spots, including one with a colour illustration. An anonymous reviewer of Koplik's The Diseases of Infancy and Childhood refers to the illustration as "the now famous coloured plate".