Morphology of Primary Skin Lesions
Accurate clinical diagnosis relies on the precise description of primary lesions. These are the “building blocks” of dermatological diagnosis.
Primary Lesion Guide
| Lesion | Size/Characteristic |
|---|---|
| Macule | Flat, < 1 cm (e.g., freckle). |
| Patch | Flat, > 1 cm. |
| Papule | Elevated, < 1 cm. |
| Plaque | Elevated, > 1 cm (often confluent). |
| Nodule | Solid, deep-seated lesion, > 1 cm. |
| Vesicle | Fluid-filled, < 1 cm. |
| Bulla | Fluid-filled, > 1 cm. |
Key Descriptive Terms
- Scale: Flaky accumulation of stratum corneum (e.g., Psoriasis).
- Crust: Dried serum, blood, or pus (e.g., Impetigo).
- Lichenification: Thickening of skin with accentuated skin markings (due to chronic rubbing).
- Excoriation: Linear erosions from scratching.
High-Yield Exam Pearl:
- Always differentiate Papule vs. Nodule by palpation: Nodules are palpable deep in the dermis/subcutis.
- When describing, follow the SCAM mnemonic: Size, Color, Arrangement, Morphology.