Lichen Planus

Description

Posterior cutaneous surfaces of the upper back and shoulders are shown in an adult male, with inflammatory erythema and clusters of violaceous papules coalescing into plaques across the scapular regions and posterior deltoids. Lesions extend laterally toward the posterior axillary folds and distally onto the proximal arms, where patchy discoloration suggests additional papular involvement along the extensor aspect. White shorts provide a clear inferior boundary at the lumbosacral level, keeping attention on the thoracodorsal distribution and the bilateral, fairly symmetric pattern. Skin texture is readable. Lichen planus is classically a pruritic, purple, polygonal, planar papular eruption, and a posterior trunk presentation like this helps teach that it is not confined to wrists and ankles. Distribution over the shoulders and back raises practical discussion points: friction from clothing and scratching can accentuate lesions via the Koebner phenomenon, and the color change on tanned skin can be misread as post-inflammatory hyperpigmentation or an eczematous process unless the papular surface is appreciated. When you need diagnostic confirmation, this pattern cues a punch biopsy from an active papule for interface dermatitis with a band-like lymphocytic infiltrate and sawtooth rete ridges; it also supports targeted history for drug-induced lichenoid eruption and screening considerations such as hepatitis C in appropriate populations. Use this image in dermatology and primary care teaching to illustrate common trunk morphology, in atlases and CME modules addressing papulosquamous differentials (psoriasis, pityriasis rosea, secondary syphilis), and in clinical documentation or patient handouts that explain chronic immune-mediated rash patterns and expected post-inflammatory pigmentary change. Anatomical accuracy verified by SciePro's Medical Advisory Board.