**Core Concept**
Tuberculosis of the skin is a cutaneous manifestation of systemic tuberculosis, caused by the bacterium *Mycobacterium tuberculosis*. It can present in various forms, each with distinct clinical features.

**Why the Correct Answer is Right**
Lupus vulgaris is the most common form of cutaneous tuberculosis, accounting for approximately 70% of cases. It is a chronic and progressive condition, characterized by the formation of large, hypertrophic, and disfiguring skin lesions. The pathogenesis of lupus vulgaris involves the bacterium's ability to invade the skin and stimulate a granulomatous response, leading to tissue destruction and scarring. The lesions typically occur on the face, neck, or arms, and can be accompanied by systemic symptoms such as fever, weight loss, and fatigue.

**Why Each Wrong Option is Incorrect**
**Option A:** Lupus vulgaris is not the same as systemic lupus erythematosus (SLE), a distinct autoimmune disease that affects multiple organ systems.
**Option B:** Lupus pernio is a form of cutaneous sarcoidosis, not tuberculosis, characterized by violaceous, indurated plaques on the nose, cheeks, and lips.
**Option C:** Lupus profundus is a form of lupus erythematosus that affects the subcutaneous fat, causing painful, subcutaneous nodules.
**Option D:** Scrofuloderma is a form of cutaneous tuberculosis that occurs due to direct extension of the infection from underlying lymph nodes or bones, rather than through the skin itself.

**Clinical Pearl / High-Yield Fact**
Lupus vulgaris is often associated with a positive Mantoux test and can be treated with antitubercular therapy, which typically involves a combination of isoniazid, rifampicin, and pyrazinamide.

**Correct Answer: A. Lupus vulgaris**