In dermatology, a plaque is a circumscribed, elevated, flat-topped, solid lesion larger than 1 centimeter (cm) in diameter. Think of it as a raised, flat area on the skin that's wider than it is thick. It's different from a papule, which is a smaller raised bump. Plaques often result from the merging of multiple papules.
Characteristics of a Plaque:
- Size: Greater than 1 cm in diameter (slightly more than ½ inch). Some sources specify greater than 10 mm.
- Shape: Typically flat-topped, although they can also be rounded.
- Texture: Solid and palpable (you can feel it).
- Elevation: Raised above the skin's surface.
Common Examples:
- Psoriasis: Plaque psoriasis is a very common example, where the plaques are often silvery-white and scaly. This is frequently cited across various sources.
- Other skin conditions: Various other skin conditions can manifest as plaques.
Key Differences from Other Lesions:
| Lesion Type | Size (approx.) | Description |
|---|---|---|
| Papule | <1 cm | Small, raised bump |
| Plaque | >1 cm | Flat-topped, raised area, wider than it is thick |
| Pustule | <1 cm | Raised, pus-filled bump |
| Nodule | >1 cm | Deeper, solid lump |
The size is a crucial differentiator between a plaque and other similar lesions. While sources slightly differ on the precise size threshold (1cm or 10mm), the overarching concept remains consistent. The merging of multiple papules can often lead to the formation of a plaque.
