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Lichenoid Skin Eruptions

»	How do lichenoid eruptions differ from other papulosquamous conditions?
»	What does “lichenoid” mean?
»	What is the most common lichenoid skin disease?
»	What anatomic locations are most often affected by Lichen planus?
»	Describe the characteristic primary skin lesions of Lichen planus.
»	What are the characteristic oral findings of Lichen planus?
»	Describe the isomorphic response of Lichen planus.
»	What causes Lichen planus?
»	What are the less common presentations of Lichen planus?
»	How is 20-nail dystrophy related to Lichen planus?
»	Is Lichen planus associated with systemic diseases?
»	What is the prognosis of Lichen planus?
»	What is the primary symptom of Lichen planus?
»	Describe the characteristic histopathologic features of classic Lichen planus.
»	How is lichen planus treated?
»	What conditions enter the differential diagnosis of an “Lichen planus-like” eruption?
»	Are Lichen planus and systemic lupus erythematosus related?
»	Are Lichen planus and bullous pemphigoid related?
»	Why is graft-versus-host disease a consideration in Lichen planus-like eruptions?
»	Describe the primary lesion of lichen nitidus.
»	What are the other clinical features of lichen nitidus?
»	Does lichen nitidus demonstrate a lichenoid infiltrate upon biopsy?
»	What is lichen striatus?
»	Discuss the natural history and prognosis of lichen striatus.
»	What is lichen simplex chronicus?
»	How is lichen simplex chronicus treated?

What are the less common presentations of Lichen planus?

Annular lichen planus on the glans was originally misdiagnosed as squamous cell carcinoma until its annular quality was noted by the dermatologist. (Courtesy of Whitney A. High, MD.)

Fig. 12.5 Annular lichen planus on the glans was originally misdiagnosed as squamous cell carcinoma until its annular quality was noted by the dermatologist. (Courtesy of Whitney A. High, MD.)

Twenty-nail dystrophy secondary to lichen planus. Note that all twenty nails demonstrate varying degrees of nail dystrophy. (Courtesy of Whitney A. High, MD.)

Fig. 12.4 Twenty-nail dystrophy secondary to lichen planus. Note that all twenty nails demonstrate varying degrees of nail dystrophy. (Courtesy of Whitney A. High, MD.)

Nail changes occur in about 10% to 15% of patients and include longitudinal ridging, irregular pitting, nail plate splitting, nail loss, and pterygium formation with severe onychodystrophy, including “20-nail dystrophy” (Fig. 12-4). Desquamative vaginitis may occur. Clinical and histologic variants of LP include annular (Fig. 12-5), hypertrophic, ulcerative, vesiculobullous, follicular, and actinic induced. LP may also involve the scalp, yielding a scarring alopecia known as lichen planopilaris.

Bhattacharya M, Kaur I, Kumar B: Lichen planus: a clinical and epidemiological study, J Dermatol 27:576–582, 2000.

Karthikenyan K, Jeevankumar B, Thappa DM: Bullous lichen planus of the glans penis, Dermatol Online J 9:31, 2003.