Oral mucosal lesion


  1. Oral mucosal lesions related to infections
  2. Recurrent aphthous stomatitis (mouth ulcers)
  3. Mucositis
  4. Vesiculo-bullous lesions (blisters)
  5. Persistent patches and lesions
  6. Oral cancer
  7. Oral mucosal lesions related to other diseases
  8. Oral mucosal lesions related to drugs

Bacterial, fungal and viral infections are common causes of oral mucosal lesions. In fact, infections of the mouth are so common that they are described and discussed in a separate section dealing with infections. Here we list common infections which typically give rise to mucosal lesions.

Oral bacterial infections include pericoronitis, alveolar osteitis (dry socket), acute and (more commonly) chronic periodontal disease, necrotising ulcerative gingivitis, dentoalveolar abscess. Scarlet fever, syphilis and tuberculosis can all give rise to oral lesions.

Viral infections with oral manifestations include herpes simplex (acute, chronic and recurrent), varicella zoster (primary causing chickenpox, later in life after dormancy causing shingles), Epstein-Barr virus (glandular fever), cytomegalovirus, coxsackie virus A (herpangina and hand, foot and mouth disease (affecting children)) and human immunodeficiency virus, HIV infections (increased risk of oral bacterial and fungal infections).

Fungal infections are almost always caused by candida species (albicans being the most common), causing acute (thrush) and chronic forms of fungal infection (candidiasis) and include opportunistic infections following treatment with broad-spectrum antibacterials or inhaled steroids (erythematous candidiasis). Chronic hyperplastic candidiasis can give rise to a form of candidal leukoplakia, persistent white patches with a tendency for abnormal cell growth (see below).

Recurrent aphthous stomatitis (mouth ulcers)

Minor aphthous ulcers are a very common condition, affecting about a third of the population, and are the most common form of mouth ulcer. The most likely cause is a combination of some (auto)immune reaction, possibly in combination with some genetic disposition; the condition occurs in familial clusters.

The small ulcers (a few mm in size) tend to appear in groups in the oral mucosa and heal, without scarring, in 1 to 2 weeks. Recurrence intervals are usually a few months, the condition is worsened by stress and is influenced by hormonal effects (such as the menstrual cycle). Occasionally such minor ulcers can be signs of other diseases (see below).

Figure 1: Top: a classical aphthous ulcer; bottom: an unusual site for an aphthous ulcer.

Major aphthous ulcers are a less common variant of mouth ulcers (about 10 % of cases), with more severe symptoms, larger ulcers and more frequent recurrences. These ulcers heal with scarring and are more often a sign of some other underlying disease (see below).

Figure 2: A major aphthous ulcer.

The least common form, herpetiform ulcers, mostly affect older females. Herpetiform ulcers resemble oral ulcers caused by viral liver infections (see below) but are not caused by infection. These ulcers occur in clusters of numerous small, painful ulcers in any area of the mouth and frequently recur over extended periods of time (sometimes several years).


Oral mucositis is a severe and painful inflammation and ulceration of the mucosa, the lining of the mouth. Mucositis can affect the entire gastrointestinal tract and is a common severe side effect of cancer treatments, both radiotherapy and chemotherapy, as well as part of a rare but serious complication after bone marrow transplants (so called graft versus host reaction). Oral mucositis can be so severe as to be a treatment-limiting effect. The mucosa is vulnerable to these effects because of its relatively high rate of tissue renewal.

Mucositis ulcers are vulnerable to infections and necrosis. Some degrees of oral mucositis occur commonly as an unwanted effect of nearly all systemic chemotherapies (with some agents, such as 5-fluorouracil, more likely to cause severe mucositis than other cytotoxic drugs) and radiotherapies. It often is particularly severe during leukaemia treatment in children (childhood leukaemias tend to be treated with aggressive chemotherapy schemes).

Mucositis caused by radiotherapy for the treatment of head and neck cancers, especially in combination with chemotherapy, tends to be particularly severe. Radiotherapy applied to the head and neck region almost always causes (variable degrees of) damage to the salivary glands, leading to problems with dry mouth, xerostomia which exacerbates the mucositis.

Oral mucositis is classified in four degrees of severity, with class 3 (only liquids can be swallowed) and class 4 (nothing can be swallowed) calling for immediate intervention by alternative feeding regimes, if not hospitalisation. There is an ongoing debate about these approaches, about the optimal overall duration, various kinds and different starting points of such feeding interventions.

Vesiculo-bullous lesions (blisters)

These are technically slightly different lesions from ulcers. Ulcers are lesions of the mucous membrane, small (vesicles) and large (bullae) blisters are lesions of the epithelium (made up by superficial cells of the thin surface lining tissue). Blisters can either interrupt the adhesion between epithelial cells (intraepithelial blisters) or detach the epithelial layer from its underlying tissue (subepithelial blisters). These intraepithelial and subepithelial blisters / lesions are by and large oral manifestations of a number of different underlying diseases (see below), with the important exception of the spontaneous formation of oral blood blisters of unknown cause (angina bullosa haemorrhagica, these are irritating but benign in nature).

Persistent patches and lesions

A number of persistent white (leukoplakia), red (erythroplakia) and speckled (erythroleukoplakia) patches, submucous fibrosis (scar tissue formation beneath the mucosa) and a rare variant of lichen planus (see below) all belong to a group of oral lesions that are associated with variable degrees of abnormal cell growth (dysplasia) and a possibility for malignant transformation of the lesion. These lesions are therefore sometimes called premalignant lesions; we discuss dysplasia in a separate section:

Lichen planus is a common skin condition (estimated 1 % of the world population), thought to be an immune disorder. It is an itchy non-infectious rash mostly affecting people older than 40 years, women are more often affected than men. Approximately in half of the cases not only the skin but also the oral mucosa is affected. Lichen planus may exclusively affect the oral mucosa.

Figure 3: Lichen planus of the skin.

Oral lichen planus typically exhibits white or reddish lace-like patterns on the surface of the tongue or inner cheek; if ulcers develop these may be painful. A biopsy may be necessary to confirm the diagnosis. A rare (approximately 1 %) sub-variant of oral lichen planus, erosive lichen planus (see Figure 4), is thought to belong to the group of potentially premalignant lesions whereas for the more common forms no such association is known. Oral lichen planus may persist for many months or years.

Figure 4: An example of oral erosive lichen planus.

Frictional keratosis is characterised by white patches caused by some minor local trauma, such as ill-fitting dentures or a sharp tooth.

Smoker’s keratosis are white patches caused by irritation by chemicals in tobacco smoke.  

Oral cancer

The majority of oral mucosal lesions are benign, but it is definitely a good idea to carefully check any persistent lesions in order to exclude malignancy. That may require taking a biopsy.

Many non-oral diseases have oral manifestations; these can be early or late signs and symptoms of other diseases. If oral manifestations happen to be an early sign of some other disease, it can (and does) happen that this disease gets initially, or tentatively, diagnosed in a maxillofacial clinic.

Apart from a wide range of infections (see above), in particular many skin diseases, haematological (blood) disorders and disorders of the gastrointestinal system lead to oral manifestations.

Skin diseases with oral manifestations include

Haematological disorders with oral manifestation include

Gastrointestinal disorders with oral manifestations include

Other conditions with oral manifestations include

The list of medicinal and recreational drugs causing, for example, difficulties with dry mouth, xerostomia is long and essentially includes every type and class of drug. Similarly, the list of drugs giving rise to other oral lesions is also long and varied, below some examples:

Further reading: Diagnosis