Aphthous ulcers, or canker sores, are the most common recurrent oral ulcers in the U.S. There are three subtypes: minor, major, and herpetiform, with minor aphthous being the most commonly reported form. These ulcers are less than a centimeter in diameter and may occur as a single ulceration or in small groups on nonkeratinized mucosa, including the lateral and ventral aspects of the tongue, floor of the mouth, soft palate, and oropharyngeal mucosa. Major aphthae and herpetiform aphthae each occur in about 10% of cases. They appear as a yellowish white round to oval ulcer with an erythematous halo.
The etiology of aphthous stomatitis is unknown. Viral, bacterial, autoimmune, allergic, and nutritional causes have been suspected. Treatment is palliative, and the minor lesions heal in 7-10 days without scarring. Major aphthae, or periadenitis mucosa necrotica recurrens, requires 2-4 weeks to heal and may do so with submucosal scarring. Topical steroids offer some hope for long-term management of recurrence.