An Introduction to Aphthous Stomatitis

What is Aphthous Stomatitis?

Aphthous: Pertaining to, characterized by, or affected with aphthae.

Aphthae is plural for aphtha which is defined by Mosby's Dental Dictionary as a small ulcer on the mucous membrane.

Stomatitis: Inflammation of the mouth.

Therefore, Aphthous Stomatitis can be defined as the inflammation of the mouth by small ulcers in the mucous membrane.

An illustration of a patient suffering from Aphthous Ulcers.
Aphthous Ulcers are more commonly referred to as Canker Sores.

According to Medscape,

"Aphthous stomatitis, or recurrent aphthous ulcers (RAUs) or canker sores, are among the most common oral mucosal lesions physicians and dentists observe. Recurrent aphthous ulcer is a disorder of unknown etiology that can cause clinically significant morbidity. One or several discrete, shallow, painful ulcers are visible on the unattached mucous membranes. Individual ulcers typically last 7-10 days. Larger ulcers may last several weeks to months and can scar when healing."

In other words, canker sores are a common phenomena among many members of the population. The condition is relatively easy to diagnose however there is a definitive lack of insight on its cause. As a result, many patients suffering from reoccurring cases face chronic pain within the oral cavity that may last anywhere from weeks to months depending on the severity of their condition. 

The classic categorization of recurrent aphthous ulcer is divided into 3 clinical forms: 

1. Recurrent aphthous ulcer minor
2. Recurrent aphthous ulcer major
3. Herpetiform recurrent aphthous ulcer.

Where does Aphthous Stomatitis affect?

Recurrent aphthous ulcer affects the following nonkeratinized or poorly keratinized surfaces of the oral mucosa:

• Labial and buccal mucosa
• Maxillary and mandibular sulci
• Unattached gingiva
• Soft palate
• Tonsillar fauces
• Floor of the mouth
• Ventral surface of the tongue

The cheeks have been cut and the lips pulled back for an unobstructed view.
Aphthous ulcers have the highest probability of forming anywhere in this diagram except the external portion of the lips and the top of the tongue.

Examples of keratinized surfaces include your skin, the top of your tongue and the external portion of your lips.

This means that a patient suffering from Aphthous Stomatitis may develop ulcers almost anywhere on the inside of their mouth such as the gums, the roof of the mouth, the sides of the mouth, the back of the mouth, the tonsils, the bottom of the mouth and the bottom of the tongue.

Where can cases of Aphthous Stomatitis be found?

In the United States, recurrent aphthouse stomatitis affects 20% of the population. 

That's about 1 in 5 people. 

Recurrent aphthous ulcers occur worldwide and are reported on every populated continent.

Who does Aphthous Stomatitis generally affect?

Farhad Melamed, MD at UCLA's Department of Medicine reports,

"There is a trend found among the population where the condition is more commonly seen in females, with a tendency to be seen in the upper socioeconomic classes."

Why does Aphthous Stomatitis occur?

"...the precise etiology and the pathogenesis of recurrent aphthous ulcer remain unclear. Many possibilities have been investigated. Recurrent aphthous ulcer is a multifactorial condition, and it is likely that immune-mediated destruction of the epithelium is the common factor in recurrent aphthous ulcer pathogenesis. Host risk factors associated with recurrent aphthous ulcer are described below."

Genetics:

A family history of recurrent aphthous ulcers is evident in some patients. A familial connection includes a young age of onset and symptoms of increased severity.

Hematinic deficiency:

In several studies, hematinic (iron, folic acid, vitamins B-6 and B-12) deficiencies were twice as common in patients with recurrent aphthous ulcers than in control subjects. As many as 20% of patients with recurrent aphthous ulcer had a deficiency.

Immune dysregulation:

At present, no unifying theory of the immunopathogenesis of recurrent aphthous ulcer exists, but immune dysregulation may play a significant role. Cytotoxic action of lymphocytes and monocytes on the oral epithelium seems to cause the ulceration, but the trigger remains unclear. Upon histologic analysis, recurrent aphthous ulcer consists of mucosal ulcerations with mixed inflammatory cell infiltrates. T-helper cells predominate in the preulcerative and healing phases, whereas T-suppressor cells predominate in the ulcerative phase.

 Microbial infection:

Researchers disagree about the role of microbes in the development of recurrent aphthous ulcers. Emphasis has been on a microbial agent as a primary pathogen or an antigenic stimulus. Numerous studies have failed to provide strong evidence to support the role of herpes simplex virus, human herpes virus, varicella-zoster virus, or cytomegalovirus in the development of aphthous ulcers.
Recurrent aphthous ulcer formation may be a T-cell–mediated response to antigens of Streptococcus sanguis that cross-react with the mitochondrial heat shock proteins and induce oral mucosa damage.

Believe it or not S. sanguinis is a normal inhabitant of the healthy human mouth where it modifies the environment to make it less hospitable for other strains of Streptococcus that cause cavities.