Monday, August 1, 2011

A NOTE ON HEREDITARY WHITE LESIONS OF ORAL MUCOSA

Leukoedema
Leukoedema is a common mucosal alteration that represents a variation of the normal condition rather than a true pathologic change. It has been reported in up to 90% of black adults and up to 50% of black teenagers. The incidence in white persons in different studies is highly variable (10 to 90%). This difference can be attributed to the darker coloration of the mucosa in black persons, rendering the alteration more visible. Similar edematous changes have been reported in other mucosal surfaces, such as the vagina and larynx.



Leukoedema with a faint white diffuse filmy appearance 
and mild wrinkling of the mucosa










FEATURES

The most frequent site of leukoedema is the buccal mucosa bilaterally, and it may be seen rarely on the labial mucosa, soft palate, and floor of the mouth. It usually has a faint, white, diffuse, and filmy appearance, with numerous surface folds resulting in wrinkling of the mucosa. It cannot be scraped off, and it disappears or fades upon stretching the mucosa. Microscopic examination reveals thickening of the epithelium, with significant intracellular edema of the stratum spinosum. The surface of the epithelium may demonstrate a thickened layer of parakeratin.

TREATMENT
No treatment is indicated for leukoedema since it is a variation of the normal condition. No malignant change has been reported.

White Sponge Nevus
White sponge nevus (WSN) is a rare autosomal dominant disorder with a high degree of penetrance and variable expressivity; it predominantly affects noncornified stratified squamous epithelium. The disease usually involves the oral mucosa and (less frequently) the mucous membranes of the nose, esophagus, genitalia, and rectum. The lesions of WSN may be present at birth or may first manifest or become more intense at puberty. Genetic analyses of families with WSN have identified a missense mutation in one allele of keratin 13 that leads to proline substitution for leucine within the keratin gene cluster on chromosome 17.9,10 A new study, using sequence analysis, has reported a  glutamine insertion localized in the helix initiation motif of the 1A alpha helical domain of Keratin 4 gene.




White sponge nevus







FEATURES
White sponge nevus presents as bilateral symmetric white, soft, “spongy,” or velvety thick plaques of the buccal mucosa. However, other sites in the oral cavity may be involved, including the ventral tongue, floor of the mouth, labial mucosa, soft palate, and alveolar mucosa. The condition is usually asymptomatic and does not exhibit tendencies toward malignant change. The characteristic histopathologic features are epithelial thickening, parakeratosis, a peculiar perinuclear condensation of the cytoplasm, and vacuolization of the suprabasal layer of keratinocytes. Electron microscopy of exfoliated cells shows numerous cellular granules composed of disordered aggregates of tonofilaments.

DIFFERENTIAL DIAGNOSIS
The lesions of WSN may be grossly similar to those of other hereditary mucosal syndromes such as hereditary benign intraepithelial dyskeratosis or pachyonychia congenita, infections such as candidiasis, traumatic lesions seen in cheek chewing, and chemical burns or preneoplastic/neoplastic processes. This differential diagnosis is best resolved in many cases by incisional biopsy specimens interpreted in the context of the clinical history and physical findings.
TREATMENT
No treatment is indicated for this benign and asymptomatic condition. Patients may require palliative treatment if the condition is symptomatic. One study has reported some relief of symptoms with a tetracycline rinse.
Hereditary Benign Intraepithelial Dyskeratosis
 Hereditary benign intraepithelial dyskeratosis (HBID), also known as Witkop’s disease, is a rare autosomal dominant disorder characterized by oral lesions and bilateral limbal conjunctival plaques. This condition is noted specifically in a triracial isolate of white, Native American, and African American people and their descendants in Halifax county, North Carolina. It exhibits a high degree of penetrance.

FEATURES
The oral lesions are similar to those of WSN, with thick, corrugated, asymptomatic, white “spongy” plaques involving the buccal and labial mucosa. Other intraoral sites include the floor of the mouth, the lateral tongue, the gingiva, and the palate. The oral lesions are generally detected in the first year of life and gradually increase in intensity until the teens. The most significant aspect of HBID involves the bulbar conjunctiva, where thick, gelatinous, foamy, and opaque plaques form adjacent to the cornea. The ocular lesions manifest very early in life (usually within the first year). Some patients exhibit chronic relapsing ocular irritation and photophobia. The plaques may exhibit seasonal prominence, with many patients reporting more pronounced lesions in the spring and regression during the summer months. A few cases of blindness due to corneal vascularization following HBID have been reported. The histopathologic features of HBID are characteristic, and the epithelium exhibits marked parakeratin production with thickening of the stratum spinosum and the presence of numerous dyskeratotic cells. Ultrastructural findings in patients with HBID reveal the the presence of numerous vesicular bodies in immature dyskeratotic cells, densely packed tonofilaments within the cytoplasm of these cells, and the disappearance of cellular bridging in mature dyskeratotic cells.

TREATMENT
Since HBID is a benign condition, no treatment is required for the oral lesions. For evaluation and treatment of the ocular lesions, the patient should be referred to an ophthalmologist.

Dyskeratosis Congenita

Dyskeratosis congenita, a recessively inherited genodermatosis, is unusual due to the high incidence of oral cancer in young affected adults. It is a rare X-linked disorder characterized by a series of oral changes that lead eventually to an atrophic leukoplakic oral mucosa, with the tongue and cheek most severely affected. The oral changes occur in association with severely dystrophic nails and a prominent reticulated hyperpigmentation of the skin of the face, neck, and chest. Many  cases also exhibit hematologic changes including pancytopenia, hypersplenism, and an aplastic or Fanconi’s anemia (ie, an anemia associated with an inherited inability to repair deoxyribonucleic acid [DNA] defects, leading to a high frequency of leukemia and lymphoma).
The oral lesions commence before the age of 10 years as crops of vesicles with associated patches of white ulcerated necrotic mucosa often infected with Candida. Erythroplakic changes and nail dystrophy follow, with leukoplakic lesions and carcinoma supervening on the oral lesions in early adulthood.

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