Uicaria pigmentosa is a disorder of ?
**Core Concept**
Urticaria pigmentosa is a condition characterized by the accumulation of mast cells in the skin, leading to hyperpigmented skin lesions and potential systemic symptoms. This disorder is a type of **mastocytosis**, which involves the proliferation and accumulation of mast cells in various tissues. The underlying principle being tested is the relationship between mast cells and skin pathology.
**Why the Correct Answer is Right**
The correct answer is related to mast cell disorders, as urticaria pigmentosa is a form of cutaneous mastocytosis. The symptoms and signs of urticaria pigmentosa, such as skin lesions and potential for anaphylaxis, are directly related to the release of histamine and other mediators from mast cells. The **KIT receptor** plays a crucial role in the pathogenesis of mastocytosis, as mutations in this receptor can lead to uncontrolled mast cell proliferation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because urticaria pigmentosa is not primarily a disorder of the nervous system.
**Option B:** This option is incorrect because, although the immune system is involved, urticaria pigmentosa is more specifically a disorder of mast cells.
**Option D:** This option is incorrect because urticaria pigmentosa is not a primary disorder of the endocrine system.
**Clinical Pearl / High-Yield Fact**
Urticaria pigmentosa is a classic example of a **mast cell disorder**, and patients with this condition are at risk for anaphylaxis, particularly if they have a large burden of mast cells. Recognizing the characteristic skin lesions and associating them with mastocytosis is crucial for diagnosis and management.
**Correct Answer:** C. Mast cells.