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A 46-year-old white man presented with an acute 3- to 4-week history of an intensely pruritic eruption that mainly involved the limbs. Individual lesions appeared to predominate around the wrist flexures. Examination revealed multiple, flat, purplish lesions, 5 to 15 mm in diameter, with coalescence in areas of scratching Figure 1. Whitish plaques were seen on the oral mucous membrane Figure 2. The patient was otherwise well, although on further questioning he stated that he felt less energetic than usual. He reported no recent illness or medication ingestion.
Figure 1
Purplish, flat-topped papules on the wrist; a few are in a linear arrangement.
Figure 2
A white reticulated pattern can be seen inside the right cheek; lesions cannot be removed with a tongue blade.
What is the diagnosis, and what further laboratory tests are indicated?
DIAGNOSIS: Lichen planus.
DISCUSSION
Lichen planus is a T-lymphocyte-mediated disease that affects both the skin and mucous membranes (1). Typically, skin lesions are pruritic, purple, polygonal, flat-topped papules that preferentially involve the flexor surfaces (especially the wrist) and trunk and only rarely involve the face (2). Close examination of a papule with a magnifying lens reveals a network of gray streaks (Wickham's striae). Rare variants of lichen planus include lesions that are hypertrophic (on the shins), bullous (on the oral mucosa), and ulcerative or erosive (on the oral mucosa, palms, and soles). The isomorphic response, or Koebner's phenomenon, is characterized by the production of lesions at areas of trauma(i.e., scratches, bites, surgical sites, and healed lesions of herpes zoster) and occurs commonly in lichen planus. Koebner's phenomenon is a helpful clinical clue because it is found in only a few dermatological diseases Table 1. Resolution of lesions may result in hyperor hypopigmentation, frequently...