Koplik spots are specific lesions that develop within the mouth. These spots are an enanthem, a term for a rash on a mucous membrane. Their appearance offers an early indication of a specific underlying condition.
What Koplik Spots Look Like
Koplik spots have a distinct appearance, often described as looking like “grains of salt on a red background”. They are small, bluish-white or gray spots, each surrounded by a reddish, inflamed halo. These spots are not usually painful or prone to forming blisters or ulcers. They measure about 2 to 3 millimeters in diameter.
The most common location for these spots is on the buccal mucosa, which is the inner lining of the cheeks. Specifically, they tend to appear opposite the first and second upper molars. In some instances, the spots can spread beyond the cheeks to other areas within the mouth, such as the soft palate or the inside of the lips. On rare occasions, they have been observed on other mucosal tissues like the conjunctiva of the eye.
The Link to Measles
The presence of Koplik spots is almost exclusively linked to the measles virus, also known as rubeola. This strong association makes them a pathognomonic sign for the disease, meaning the spots point definitively to a single condition. Their appearance helps differentiate measles from other infections that may present with a rash.
Because these spots are so specific to measles, they provide a diagnostic clue for clinicians. Their identification allows for an early diagnosis of the infection, often before the full-body rash becomes apparent. This early recognition is important for managing the highly contagious disease. Koplik spots are observed in 60% to 70% of individuals with measles, making them a common, though not universal, feature.
Timeline Within the Measles Infection
Koplik spots emerge during the prodromal stage of the measles infection, the initial period of symptoms before the main illness is fully developed. The spots typically appear one to four days before the characteristic skin rash begins to erupt on the face and body.
The lifespan of Koplik spots is brief. They are a transient phenomenon, usually remaining visible for only two to three days. Their disappearance often coincides with the progression of the skin rash. As the full-body rash spreads, the spots on the buccal mucosa fade and the tissue reverts to its normal appearance.