ESSENTIALS OF DIAGNOSIS
Pruritic, violaceous, flat-topped papules with fine white streaks and symmetric distribution.
Lacy or erosive lesions of the buccal, vulvar, and vaginal mucosa; nail dystrophy.
Commonly seen along linear scratch marks (Koebner phenomenon) on anterior wrists, penis, and legs.
Lichen planus is an inflammatory pruritic disease of the skin and mucous membranes characterized by distinctive papules with a predilection for the flexor surfaces and trunk. The three cardinal findings are typical skin lesions, mucosal lesions, and histopathologic features of band-like infiltration of lymphocytes in the upper dermis. Lichenoid drug eruptions can resemble lichen planus clinically and histologically. The most common medications include sulfonamides, tetracyclines, quinidine, NSAIDs, beta-blockers, and hydrochlorothiazide. Hepatitis C infection is found with greater frequency in lichen planus patients than in controls. Allergy to mercury and other metal-containing amalgams can trigger oral lesions identical to lichen planus.
The lesions are violaceous, flat-topped, angulated papules, up to 1 cm in diameter, discrete or in clusters (Figure 6–26) (eFigure 6–79), with very fine white streaks (Wickham striae) on the flexor surfaces of the wrists and ankles; on lower back; and on mucous membranes, including the penis, lips, tongue, buccal, vulvar, vaginal, esophageal, and anorectal mucosa. Itching is mild to severe. The papules may become bullous or eroded. The disease may be generalized. Mucous membrane lesions have a lacy white network overlying them that may be confused with leukoplakia. The presence of oral and vulvovaginal lichen planus in the same patient is common. Patients with both these mucous membranes involved are at much higher risk for esophageal lichen planus. Lichen planus is also a cause of alopecia and nail dystrophy. The Koebner phenomenon (appearance of lesions in areas of trauma) may be seen.
Hypertrophy—hypertrophic lichen planus. (Reproduced with permission from Richard P. Usatine, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley HS. The Color Atlas and Synopsis of Family Medicine, 3rd ed. McGraw-Hill, 2019.)
Lichen planus. (Used, with permission, from TG Berger, MD, Dept Dermatology, UCSF.)
A special form of lichen planus is the erosive or ulcerative variety, a major problem in the mouth or genitalia. Squamous cell carcinoma develops in up to 5% of patients with erosive oral or genital lichen planus and may occur in esophageal lichen planus. There is also an increased risk of squamous cell carcinoma developing in lesions of hypertrophic lichen planus on the lower extremities.
Lichen planus must be distinguished from similar lesions produced by medications and other papular lesions, such as psoriasis, lichen simplex chronicus (eFigure 6–80) ...