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Oral Infections |
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The mouth is largely lined by non-keratinizing
squamous epithelium, but there is abundant scattered salivary tissue located in the sub-mucosa, with ducts opening into the surface. The mouth comprises the lips, the buccal cavity,
the palate, the tongue, the alveolar ridges of the mandible and maxilla
(in which the teeth are embedded), the teeth, and Waldeyer's ring, which is formed by the lymphoid tissue of the posterior tongue, the palatine tonsils,
and the oropharynx.
Cleft palate and cleft lip are the most common major congenital malformations
of the mouth.
Cleft palate and cleft lip frequently occur together, as they arise as a result of the same process, i.e. a failure of fusion of embryological
midline structures at about eight weeks' gestation.
A few cases are associated with a chromosomal abnormality (e.g. trisomies
13 and 18), but the teratogenic factors cannot usually be identified in
individual cases.
In minor degrees of cleft palate, only the soft palate is cleft, the most obvious feature on examination being a bifid uvula.
Severe degrees also affect the bone of the hard palate, and the cleft may
involve the alveolar ridge, in which case there is co-existent cleft lip.
A high, arched palate is a very frequent minor congenital abnormality. It is
usually asymptomatic, although there may be a predisposition to middle-ear infections and sinusitis.
Most infections of the lips and buccal cavity (infective stomatitis) are due to either viruses or fungi
Viral infections of the lips and mouth usually manifest as large blisters or crops of small, painful vesicles, which eventually erode to form shallow, tender ulcers.
Herpes virus Type 1 produces herpetic stomatitis. Blisters develop on
the gingiva and palate in the early stages, leaving shallow ulcers after rupture.
Severe herpetic stomatitis is important in immunosuppressed patients,
particularly AIDS patients. Herpes labialis (coldsore) is the result of viral
latency, with re-activation of previous virus infection producing vesicle formation at the mucocutaneous borders of the upper and lower lips.
Herpes zoster may affect the mouth when the disease involves the trigeminal nerve ('trigeminal shingles'), producing clusters of vesicles
in the mouth, invariably unilaterally.
In infectious mononucleosis the Epstein-Barr virus(glandular fever)
most commonly produces symptoms at the back of the mouth, particularly in
the tonsils and pharynx. However, the anterior part of the oral cavity may
show small petechial haemorrhages, usually on the palatal mucosa.
Coxsackie A virus produces tiny vesicles in the mouth, with small vesicles in the skin of the hands and, occasionally, that of the feet (hand, foot and mouth disease).
This transient, mild infection is mainly seen in children, often in school-based epidemics.
Fungal infection of the mouth with Candida albicans is common
Candida albicans infection of the mouth is most frequently seen in infants
in the form of 'thrush'. It is manifest as white patches on the palatal
buccal, and tongue surfaces; the white patches are
composed of tangled fungal hyphae mixed with acute
inflammatory cells and some desquamated epithelium. The underlying epithelium
is acutely inflamed and red, a feature that becomes apparent when the white
patch is scraped away.
In adults, acute candidal infection of the mouth is less common unless there
are predisposing factors such as diabetes mellitus, immunosuppressive therapy,
or a natural immunosuppressed state, for example in advanced malignancy or with HIV infection. However, denture stomatitis, due to Candida lodging under the denture plate, is not uncommon in adults with no other
predisposing factors.
Infective stomatitis due to bacteria is now rare
Bacterial infections are common and important at the back of the mouth and
oropharynx. However, although dental caries and periodontal disease are a
consequence of bacteria present on and around the teeth, bacterial infections
of the front of the mouth are now uncommon.
Acute necrotizing ulcerative gingivitis occurs mainly in young males with poor dental hygieneز There is acute sloughing ulceration of the interdental papillae, which rapidly spreads along the gingival margins, producing an expanding area of yellow slough surrounded by a narrow zone of hyperaemic mucosa, which often bleeds heavily.
The gingiva are very painful, and the breath smells foul. Extension of
the necrosis and inflammation leads to destruction of the periodontal tissues.
The necrotic areas are heavily populated by a mixture of fusiform
and spirochaetal organisms (Fusobacterium and Borrelia species),
which are probably the causative organisms.
Secondary syphilis, which causes characteristic snail-track ulcers
in the buccal mucosa, was formerly an important cause of mucosal ulceration,
as was tertiary syphilis, in which the palate ulcerates over a destructive
gumma in the palatal bone. These are now rare manifestations of syphilis in the mouth, but the primary syphilitic lesion, the chancre, is still occasionally seen, usually on the lip or tongue.
In the Third World, overwhelming bacterial cellulitis of the mouth and the destructive bacterial gingivitis known as cancrum oris are still occasionally seen.
Not all types of stomatitis are infective
The most common type of inflammation of the lips, tongue and buccal mucosa
is that associated with aphthous ulceration. Tiny, painful, shallow ulcers form against a background of red mucosa.
The ulcer
crater is covered by a creamy exudate composed of fibrin and inflammatory cells, mainly neutrophils. The ulcers are recurrent but of short duration.
Large ulcers (up to 3 cm across) occasionally occur, sometimes persisting
for several weeks before healing with fibrosis. However, this is a much less common variant.
Oral ulcers that are clinically and histologically identical to aphthous ulcers are a feature of Behçet's syndrome. There is associated ulceration
of the genital mucosa, which is usually extensive and painful. In this syndrome the ulcers do not resolve quickly without treatment, and are often
refractory to the treatments that normally improve ordinary aphthous ulcers.
The cause of aphthous ulcers is not known.
Many common skin diseases can affect the oral mucosa
The skin diseases that most frequently involve the oral mucosa are lichen planus,
erythema multiforme, discoid lupus erythematosus (DLE) and systemic lupus erythematosus (SLE), pemphigus vulgaris, and pemphigoid.
Of these, oral lichen planus is the most common, presenting with white lines
against a background of a red buccal mucosa. The disease may also
affect the tongue and gingiva. Unlike lichen planus in the skin, erosion (due to separation of the epidermis) is common in the mouth.
The disease may be particularly chronic, with older lesions producing patchy areas of
white thickening. The histological appearances are similar to those seen
in the skin.
There is a dense lichenoid inflammatory
infiltrate associated with degeneration of the basal layer of the epithelium;
occasional Civatte bodies represent dead basal keratinocytes.
In buccal and gingival lesions the overlying epidermis is frequently very thin.
Erythema multiforme in the mouth is probably most often seen as an
adverse drug reaction. However, spontaneous episodes without a drug history are seen, particularly in children and juveniles in whom no obvious causative
factor can be identified, although some follow a viral illness.
The lesions
range from small, red mucosal areas with central blisters, to very extensive
erosive blistering lesions. The latter pattern is sometimes called Stevens-Johnson syndrome.
Unlike the skin lesions, erythema multiforme
in the mouth nearly always blisters.
Oral involvement in SLE} and DLE produces ulcerated and erosive lesions
that can be clinically and histologically difficult to distinguish from lichen
planus.
The histological appearances of pemphigus vulgaris and pemphigoid are typical: both produce blisters and mucosal erosions. |
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