What is Aphthous Stomatitis?

atypical CAPS mouth ulcer

Mouth ulcer in an atypical CAPS patient. Mouth ulcers are a common fever syndrome symptom.

Aphthous stomatitis and aphthous ulcer are medical terms for canker sore. Autoinflammatory patients and doctors often call these mouth or oral ulcers. These ulcers develop inside the mouth. They are usually white to cloudy white surrounded by a halo of red inflamed tissue. They can occur anywhere in the mouth, including on the gums, tongue, inside of the cheeks, inner parts of the lip, and on the throat.

What Causes Mouth Ulcers?

Mouth ulcers are not uncommon in the general population. In general, they are more common in women.  They can be triggered by something as simple as irritation from food or drinking too hot of coffee. However, they are also a common symptom of many inflammatory diseases, both autoimmune and autoinflammatory, such as lupus, rheumatoid arthritis, and periodic fever syndromes.

In autoinflammatory diseases, mouth ulcers may develop only with the flare or in between flares in some individuals. Of the autoinflammatory conditions, Behçet’s, PFAPA (periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis), HIDS (hyper-IgD syndrome), and DIRA are often noted for having mouth ulcers as a symptom. Patients with FMF, TRAPS, and those with undifferentiated fever syndromes also have reported having mouth ulcers.

Mouth ulcers are not contagious.

Cold Sore vs. Canker Sore

canker sore

Cold sores are on the outside of the mouth and caused by a herpes virus. Photo by quayside/Bigstockphoto.com

Cold sores are outside the mouth. Canker sores are inside the mouth.

Canker sores, aka mouth ulcers, are not the same as cold sores. Except for the very first infection, which may occur inside the mouth according to the University of Michigan Health Service, cold sores develop on the outside of the lip or skin right next to the lip. They may also develop on the cheeks, nose, and even eyelids. They start as clear blisters, then become cloudy, and eventually scab over before disappearing. Cold sores are caused by a herpes virus and in many people will become recurrent, coming and going throughout a person’s lifetime. Cold sores are contagious.

Cold sores are not a symptom of autoinflammatory conditions. However, if a person has a periodic fever syndrome and the herpes virus that causes cold sores, flares and fevers may cause the reactivation of the cold sores.

Mouth Ulcer Treatment

Aphthous stomatitis, aka mouth ulcers, can be very painful. In some individuals they can become so numerous and painful that eating and drinking becomes very difficult. Treatment of the underlying autoinflammatory condition should control, or at least help reduce the oral lesions. However, some patients need to treat the oral ulcers directly. Click here to see the treatment options for aphthous stomatitis.


  1. WebMD: Stomatitis
  2. University of Michigan University Health Service: Cold and Canker Sores
  3. MedlinePlus: Mouth Ulcers

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