Aphthous ulcers, often called canker sores, are painful inflammatory lesions or spots on the inside of the mouth.
Most often, people develop minor aphthous ulcers, which is where the lesions are a few millimeters across, round or oval in shape, and disappear within a week.
There are also two other unusual variations, however, major aphthous ulcers and herpetiform ulcers, which are much more severe and debilitating.
The underlying cause of this inflammatory disease is not well understood. One theory suggests tissue specific autoimmunity, where a localized cell-mediated immune reaction happens in the oral mucosa creating an accumulation of T-cells, specifically T helper cells Th1 cells, and macrophages, as well as chemokines like interferon-gamma and tumor necrosis factor.
Aphthous ulcers typically arise, either singly, or a few at a time, on the inside of the lips and cheeks or under the tongue.
Initially there is a small raised bump of inflammation in your mouth, and as it heals it turns into an ulcer covered by a fibrous membrane “cap” that looks yellowish-white or gray with well defined margins.
The ulcer is typically surrounded by a characteristic red halo due to inflammation in neighbouring blood vessels.
Aphthous ulcers are usually mildly painful and annoying, with individual lesions measuring a few millimeters across and healing within 7 to 10 days without scarring. And these usually recur 3-4 times per year.
There are some variations on this general pattern. Some individuals have recurrent aphthous ulcers which is where the recurrence is more frequent - sometimes each month, and this starts during childhood and resolves around age 40.
Another variation is major aphthous ulcers which describes lesions that measure over one centimeter in size and are generally more painful, last longer, and recur frequently.