Koplik spots are a prodromic viral enanthem of measles manifesting two days before the measlesrash itself. They are characterized as clustered, white lesions on the buccal mucosa (on the buccal mucosa opposite the lower§ 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.
Some authors ascribe the first written description of these spots to Reubold, Würzburg 1854, and others to Johann Andreas Murray (1740-1791). Before Koplik, the German internist Carl Jakob Adolf Christian Gerhardt (1833-1902) in 1874, the Danish physician N. Flindt in 1879, and the Russian Nil Filatov (1847-1902) in 1895, had observed equivalent phenomena.