Fig. 1.5 Verrucous leukoplakia on the dorsum of the tongue.
1.2 Hairy Leukoplakia
Definition: Hairy leukoplakia was, during the pre-ART (antiretroviral therapy) era, one of the most common (20–30%) and characteristic lesions of human immunodeficiency virus (HIV) infection, while currently it appears less often. In HIV-infected patients, hairy leukoplakia develops when the CD4 count is less than 500 cells/mm3. In addition, it can also appear in immunosuppressed patients mainly after organ transplantation.
Etiology: The lesion is caused by Epstein–Barr virus.
Clinical features: Clinically, hairy leukoplakia presents as a white, asymptomatic, often elevated and unremovable patch. The lesion is almost always found bilaterally on the lateral margins of the tongue, and may spread to the dorsum and the ventral surface (▶ Fig. 1.6). Characteristically, the surface of the lesion is corrugated with a vertical orientation to the long axis of the tongue. However, smooth and flat lesions may also be seen. The lesion is not potentially malignant (precancerous).
Laboratory tests: Histologic examination, in situ hybridization, polymerase chain reaction, and electron microscopy are useful diagnostic tests.
Differential diagnosis: Leukoplakia, cinnamon contact stomatitis, uremic stomatitis, lichen planus, candidiasis, chemical burn, frictional keratosis, leukoedema, and lupus erythematosus.
Treatment: Usually, no treatment is required. However, in extent and severe cases acyclovir or valaciclovir or famciclovir can be used with success.
Fig. 1.6 Oral hairy leukoplakia.
1.3 Lichen Planus
Definition: Lichen planus is a relatively common, chronic inflammatory disease of the oral mucosa, skin, genital mucosa, nails, and hair.
Etiology: The exact etiology is not well known. However, T-cell-mediated immune reaction against components of epithelial basal cells may be involved.
Clinical features: Clinically, oral lichen planus classically presents with small white papules that coalesce, forming a network of lines usually in a symmetrical pattern (Wickman’s striae). Six forms of oral lichen planus are recognized: the reticular and erosive or ulcerative that are common (▶ Fig. 1.7 and ▶ Fig. 1.8), the atrophic and hypertrophic that are less common (▶ Fig. 1.9 and ▶ Fig. 1.10), and the bullous and pigmented (▶ Fig. 1.11 and ▶ Fig. 1.12) that are rare. Frequently, the erosive and atrophic forms involve the gingiva in the pattern of desquamative gingivitis.
Clinically, the cutaneous lichen planus appears as small, flat, polygonal, shiny papules with characteristic violaceous color, associated by pruritus (▶ Fig. 1.13). The lesions are distributed in a symmetrical pattern, more frequently on the flexor surfaces of the forearms and wrists, the neck, the back, and the sacral area. Linear lesions may develop after scratching the skin (Koebner’s phenomenon). Genitalia and nails may also be affected. Oral lichen planus may follow a course of remissions and exacerbations. The buccal mucosa, tongue, gingiva, and lips are most commonly affected. Middle-aged individuals are more frequently affected, with a female-to-male ratio of 2:1. The diagnosis usually is based on clinical grounds alone. The prognosis of oral lichen planus is usually good, as possibility of malignant transformation is very rare and controversial.
Laboratory tests: Biopsy and histologic examination are helpful. Direct immunofluorescence can also be used.
Differential diagnosis: Fordyce’s spots, chemical burn, candidiasis, lichenoid reaction to drug or dental material, cinnamon contact stomatitis, geographic tongue, leukoplakia, erythroplakia, graft versus host disease, discoid lupus erythematosus, secondary syphilis, mucous membrane pemphigoid, other chronic bullous diseases, and chronic ulcerative stomatitis.
Treatment: Mild, asymptomatic forms of lichen planus do not need therapy. Systemic corticosteroids (e.g., prednisolone 20–40 mg/day) are the drugs of choice in severe, symptomatic cases, particularly in the erosive form. Topical corticosteroids and/or tacrolimus in a 0.5% adhesive ointment form are suggested in less severe cases. The topical use of antiseptic mouthwashes should be avoided.
Fig. 1.7 Lichen planus, reticular type on the buccal mucosa.
Fig. 1.8 Lichen planus, erosive type on the dorsum of the tongue.
Fig. 1.9 Lichen planus, atrophic type on the dorsum of the tongue.
Fig. 1.10 Lichen planus, hypertrophic lesions with a central erosion on the buccal mucosa.
Fig. 1.11 Lichen planus, bullous type on the buccal mucosa.
Fig. 1.12 Lichen planus, pigmented lesion on the buccal mucosa.
Fig. 1.13 Lichen planus, typical lesions on the forearm.
1.4 Lichenoid Reactions
Definition: Lichenoid reactions are a heterogeneous group of lesions of the oral mucosa that exhibit clinical and histopathological similarities to oral lichen planus, but have a different clinical course.
Etiology: Persistent, chronic contact of the oral mucosa with amalgam restorations that have been oxidized, may lead to hypersensitivity or toxic reaction, usually due to mercury and rarely to other trace metals (zinc, copper, silver, and tin). Similar reactions may appear after contact with composite resin, dental plaque accumulation, and systemic drug administration.
Clinical features: Clinically, lichenoid reaction appears as white and/or erythematous lesions, usually associated with peripheral, irregular delicate white striae (▶ Fig. 1.14 and ▶ Fig. 1.15). Occasionally, erythema and erosions may develop, associated with pain and a burning sensation, particularly to certain foods and spices. Characteristically, the lesions develop exactly at the sites of contact of the oral mucosa with the restorative material, and do not migrate to other sites. The clinical and histopathological features are similar to lichen planus. The buccal mucosa and the lateral margins of the tongue are the most frequently affected. Classically, the lesions disappear after removal of the responsible restorative material. The diagnosis is usually based on the history and clinical features.
Laboratory tests: Histopathologic examination is useful. In addition, a skin punch biopsy to detect the suspicious material may be helpful.