**Core Concept**
Cutaneous tuberculosis is a form of extrapulmonary tuberculosis that affects the skin. It can manifest in various ways, including lesions, ulcers, nodules, or plaques. Cutaneous tuberculosis is usually a result of the reactivation of latent tuberculosis infection or through hematogenous spread from a distant site.

**Why the Correct Answer is Right**
Erythema induratum (also known as Bazin's disease) is a type of cutaneous tuberculosis that primarily affects the lower legs. It is characterized by the formation of indurated, painful nodules or plaques that often suppurate and leave scars. The pathophysiology of erythema induratum is thought to be related to the obstruction of lymphatic vessels by granulomatous inflammation, leading to ischemia and necrosis of the overlying skin.

**Why Each Wrong Option is Incorrect**
**Option A:** Lupus vulgaris is the most common form of cutaneous tuberculosis, but it typically presents as large, chronic plaques or nodules on the face, neck, or arms, rather than the lower extremities.

**Option B:** Tuberculid is a term used to describe cutaneous reactions to an internal focus of tuberculosis, such as erythema induratum. However, it is not a specific type of cutaneous tuberculosis.

**Option C:** Scrofuloderma is a form of cutaneous tuberculosis that results from the direct extension of tuberculosis from an underlying focus, such as a lymph node or bone. It typically presents as indurated, painless ulcers or nodules on the skin.

**Clinical Pearl / High-Yield Fact**
Erythema induratum is often associated with systemic symptoms such as fever, weight loss, and malaise, and may be a manifestation of underlying tuberculosis infection.

**Correct Answer: C. Scrofuloderma**