Which clinical feature best distinguishes lichen planus from lichen nitidus?

Explanation

## Distinguishing Lichen Planus from Lichen Nitidus ### Key Clinical Discriminator **Key Point:** Wickham striae (fine, white, lacy lines visible on the surface of lesions) are pathognomonic for lichen planus and are absent in lichen nitidus. ### Comparative Features | Feature | Lichen Planus | Lichen Nitidus | |---------|---------------|----------------| | **Lesion size** | 2–10 mm papules | <1 mm papules (pinhead-sized) | | **Wickham striae** | Present (white lacy lines) | Absent | | **Color** | Violaceous, shiny | Flesh-colored or slightly erythematous | | **Distribution** | Flexural surfaces, oral mucosa, genitals | Generalized, dorsal hands/forearms | | **Histology** | Wedge-shaped hypergranulosis, dense band-like lymphocytic infiltrate | Focal lymphocytic infiltrate ("ball in cup" appearance) | | **Pruritus** | Often severe | Minimal or absent | | **Oral involvement** | Common (reticular, erosive forms) | Rare | | **Malignant potential** | Oral form has risk of SCC | None | ### High-Yield Mnemonic **Mnemonic: "WICKED LP"** — **W**ickham striae, **I**nflammatory, **C**oarse papules, **K**eratotic, **E**rosive (oral), **D**ark violaceous — all features of Lichen Planus. ### Clinical Pearl **Clinical Pearl:** Wickham striae are best seen under magnification (dermoscopy or hand lens) on the surface of violaceous papules. This finding, combined with the larger size of lesions (2–10 mm), reliably separates lichen planus from the pinhead-sized, non-striated lesions of lichen nitidus. ### Pathophysiologic Basis Wickham striae represent focal areas of hyperkeratosis and hypergranulosis overlying the dermal infiltrate in lichen planus. This histologic pattern is unique to lichen planus and does not occur in lichen nitidus, which shows a more focal, superficial lymphocytic infiltrate without prominent surface changes. [cite:Robbins 10e Ch 25]