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For further information, see CMDT Part 6-41: Lichen Planus
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Essentials of Diagnosis
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Pruritic, violaceous, flat-topped papules with fine white streaks and symmetric distribution
Lacy or erosive lesions of the buccal and vaginal mucosa; nail dystrophy
Commonly seen along linear scratch marks (Koebner phenomenon) on anterior wrists, penis, legs
Histopathologic examination is diagnostic
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General Considerations
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A relatively common (affecting 0.39% of the population in the United States) chronic inflammatory pruritic disease of the skin and mucous membranes characterized by distinctive papules with a predilection for the flexor surfaces and trunk
Three cardinal findings
Lichenoid drug eruptions can resemble lichen planus clinically and histologically
Most common medications include
Hepatitis C infection is associated with increased prevalence of lichen planus
Allergy to mercury and other metal containing amalgams can trigger oral lesions identical to lichen planus
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Itching is mild to severe
Skin lesions
Are violaceous, flat-topped, angulated papules, 1–4 mm in diameter
Are discrete or in clusters
Contain very fine white streaks (Wickham striae) on the
Flexor surfaces of the wrists and ankles
Lower back
Mucous membranes, including the penis, lips, tongue, buccal, vulvar, vaginal, esophageal, and anorectal mucosa
Mucous membrane lesions have a lacy white network overlying them that may be confused with leukoplakia
Mucosal lichen planus in the oral, genital, and anorectal areas may be erosive or ulcerative
The papules may become bullous and eroded
The disease may be generalized
Patients with both oral and vaginal lichen planus are at much higher risk for esophageal lichen planus
The Koebner phenomenon (appearance of lesions in areas of trauma) may be seen
Can cause alopecia and nail dystrophy
Squamous cell carcinoma
Develops in 5% of patients with erosive oral or genital lichen planus
May occur in esophageal lichen planus
Risk increased in lesions of hypertrophic lichen planus on the lower extremities
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Differential Diagnosis
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Lichenoid drug eruption
Psoriasis
Lichen simplex chronicus
Secondary syphilis
Pityriasis rosea
Discoid lupus erythematosus
Graft-versus-host disease
Mucosal lesions
Leukoplakia
Candidiasis
Erythema multiforme
Pemphigus vulgaris
Bullous pemphigoid
Lichen sclerosus
Lichen planus on the mucous membranes must be differentiated from leukoplakia; erosive oral lesions require biopsy and often direct immunofluorescence for diagnosis since lichen planus may simulate other erosive diseases
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