Secondary Skin Lesions
Secondary lesions are changes that occur as a result of the evolution of a primary lesion, external trauma, or the natural progression of a skin disease. Identifying these is crucial for diagnosis and staging.
Common Secondary Lesions
| Lesion | Description |
|---|---|
| Scale | Accumulation of keratinized skin cells; often seen in psoriasis. |
| Crust | Dried serum, pus, or blood (e.g., “honey-colored” crust in impetigo). |
| Excoriation | Linear erosions due to scratching; hallmark of pruritic conditions. |
| Lichenification | Thickened, leathery skin from chronic rubbing/scratching. |
| Atrophy | Thinning of skin; it can appear shiny or “cigarette-paper” like. |
Diagnostic Pearls
- Fissure: A linear crack in the skin, often extending into the dermis (e.g., chapped hands, athlete’s foot).
- Erosion vs. Ulcer: Erosions are superficial (epidermis only) and heal without scarring; ulcers extend into the dermis/subcutis and typically leave a scar.
High-Yield Exam Pearl:
- Lichenification: This is the classic “itch-scratch cycle” response. If you see it, look for an underlying chronic dermatitis like Atopic Dermatitis.
- Scarring: Always differentiate hypertrophic scars from keloids; keloids grow *beyond* the borders of the original injury.