Comedo nevus is which type of epidermal nevus –
**Core Concept**
A comedo nevus, also known as a nevus comedonicus, is a rare congenital epidermal nevus characterized by an abnormal proliferation of keratinocytes and sebaceous glands, leading to comedone-like lesions. This condition is a type of hamartoma, a benign growth composed of an abnormal mixture of cells and tissues normally found in the area of the body where the growth occurs.
**Why the Correct Answer is Right**
Comedo nevus is a type of epidermal nevus that presents with multiple comedones, which are open or closed follicular orifice lesions filled with keratin debris and sebum. The pathogenesis of comedo nevus is thought to involve an abnormality in the development of the pilosebaceous unit, leading to an overgrowth of keratinocytes and sebaceous glands. Histologically, comedo nevus shows an increased number of sebaceous glands and keratin cysts, which can lead to the formation of comedones.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the type of epidermal nevus known as comedo nevus.
* **Option B:** This option is incorrect because it is a different type of epidermal nevus, characterized by an abnormal growth of blood vessels.
* **Option C:** This option is incorrect because it refers to a type of epidermal nevus that presents with multiple epidermal nevi, not comedones.
**Clinical Pearl / High-Yield Fact**
It is essential to recognize that comedo nevus is a rare congenital condition that can be associated with other systemic abnormalities, such as neurofibromatosis or basal cell nevus syndrome. A thorough medical history and physical examination are crucial in making an accurate diagnosis.
**Correct Answer: A. Comedo nevus is a type of epidermal nevus characterized by an abnormal proliferation of keratinocytes and sebaceous glands, leading to comedone-like lesions.**