Biopsies for routine histologic examination and direct immunofluorescence are useful for distinguishing these disorders from oral LP. Graft-versus-host disease (GVHD)
Lacy, reticulated plaques or erosions that resemble oral LP may occur in GVHD. The histologic findings of these disorders are also similar. The patient history is useful for differentiating chronic GVHD from oral LP. Oral involvement in acute GVHD is less well characterized than chronic GVHD, but has been associated with erythematous, erosive, ulcerative, or lichenoid oral lesions. Leukoplakia
Leukoplakia is a manifestation of squamous epithelial hyperplasia that may be a precursor to oral squamous cell carcinoma. White patches or plaques usually appear on the oral mucosa. To rule out malignancy, a biopsy of leukoplakia is indicated. Oral squamous cell carcinoma
Oral squamous cell carcinoma (SCC) can present as erythematous or white patches, ulcers, or exophytic masses. The highest risk for oral SCC may occur in patients with erythematous or erosive oral LP. A biopsy is indicated. Leukoedema
Leukoedema is a common, benign finding in the oral cavity that presents as white-gray, somewhat translucent plaques on the mucosa. The buccal mucosa is the most common site for involvement. Symptoms are absent, and no treatment is necessary. Oropharyngeal candidiasis
Oropharyngeal candidiasis (also known as thrush) is a common infection that has a predilection for infants, older adults with dentures, immunosuppressed individuals, and individuals utilizing intraoral corticosteroid therapy. Patients present with white plaques or erythematous patches on the buccal mucosa, palate, tongue, or oropharynx that may be mistaken for reticular LP.
Mucosal forms are those affecting the lining of the gastrointestinal tract (mouth, pharynx, esophagus, stomach, anus), larynx, and other mucosal surfaces including the genitals, peritoneum, ears, nose, bladder and conjunctiva of the eyes. Pattern
Lichen planus lesions can occur in many different forms:

Overlap syndromes
Occasionally, lichen planus is known to occur with other conditions. For example:

Lupus erythematosus overlap syndrome. Lesions of this syndrome share features of both lupus erythematosus and lichen planus. Lesions are usually large and hypopigmented, atrophic, and with a red to blue colour and minimal scaling. Telangectasia may be present. Lichen sclerosus overlap syndrome, sharing features of lichen planus and lichen sclerosus. Signs and symptoms
Although lichen planus can present with a variety of lesions, the most common presentation is as a well defined area of purple-coloured, itchy, flat-topped papules with interspersed lacy white lines (Wickhams striae). This description is known as the characteristic "6 Ps" of lichen planus: planar (flat-topped), purple, polygonal, pruritic, papules, and plaques. This rash, after regressing, is likely to leave an area of hyperpigmentation that slowly fades. That said, a variety of other lesions can also occur. Skin
Variants of cutaneous lichen planus are distinguished based upon the appearance of the lesions and/or their distribution. Lesions can affect the:

Extremities (face, dorsal hands, arms, and nape of neck). This is more common in Middle Eastern countries in spring and summer, where sunlight appears to have a precipitating effect. Palms and soles
Intertriginous areas of the skin. This is also known as "inverse lichen planus."