Psoriasis is characterised by
**Core Concept**
Psoriasis is a chronic inflammatory skin disease characterized by accelerated epidermal turnover and abnormal immune response. It involves a complex interplay between keratinocytes, T lymphocytes, and other immune cells, leading to the formation of scaly, erythematous plaques.
**Why the Correct Answer is Right**
The correct answer involves the concept of hyperproliferation of keratinocytes, which is a hallmark of psoriasis. This is due to the abnormal regulation of cell cycle and differentiation in the epidermis. The immune system plays a crucial role in this process, with activated T lymphocytes (especially Th1 and Th17 cells) producing cytokines such as TNF-α, IL-17, and IL-22, which further exacerbate the inflammation and keratinocyte proliferation.
**Why Each Wrong Option is Incorrect**
* **Option A:** Not a characteristic of psoriasis, as it is primarily associated with a decrease in the lifespan of keratinocytes.
* **Option B:** While inflammation is a feature of psoriasis, it is not the most distinctive characteristic of the disease.
* **Option C:** Not a specific characteristic of psoriasis, as it can be seen in various other skin conditions.
**Clinical Pearl / High-Yield Fact**
One key aspect of psoriasis is the involvement of the immune system, particularly the Th1 and Th17 pathways. Understanding this pathophysiology is crucial for developing effective treatment strategies, such as biologic agents targeting TNF-α and IL-17.
**Correct Answer:** D. Hyperproliferation of keratinocytes.