**Core Concept**
Lupus vulgaris is a form of cutaneous tuberculosis, a chronic and progressive skin condition caused by the bacterium Mycobacterium tuberculosis. It is a manifestation of tuberculosis, characterized by the formation of nodules, plaques, and ulcers on the skin.

**Why the Correct Answer is Right**
Lupus vulgaris is indeed TB of the skin and mucosa, resulting from the hematogenous spread of M. tuberculosis to the skin. The condition often presents with disfiguring lesions, particularly on the face, and can lead to significant morbidity. The classic "apple jelly" nodule, which is a characteristic feature of lupus vulgaris, is due to the presence of caseous necrosis within the lesions. The term "scrofuloderma" refers to another form of cutaneous tuberculosis, where the bacteria directly invade the skin from adjacent infected lymph nodes.

**Why Each Wrong Option is Incorrect**
* **Option A:** Apple jelly nodule is a characteristic feature of lupus vulgaris, but it is not exclusive to the root of the nose. Lesions can occur anywhere on the body.
* **Option C:** Scrofuloderma is a different form of cutaneous tuberculosis, characterized by the direct invasion of skin from adjacent infected lymph nodes. It is not synonymous with lupus vulgaris.
* **Option D:** ATT (Anti-Tubercular Therapy) is indeed helpful in treating lupus vulgaris, but the question asks for a true statement about the condition itself, not its treatment.

**Clinical Pearl / High-Yield Fact**
Lupus vulgaris is a chronic and progressive form of cutaneous tuberculosis, often requiring long-term ATT to prevent further damage and scarring. It is essential to differentiate it from other forms of cutaneous tuberculosis, such as scrofuloderma, to provide appropriate treatment.

**Correct Answer:** B. TB of skin & mucosa