**Core Concept**
"En coup de sabre" is a rare skin condition characterized by unilateral atrophy and scarring of the skin, typically affecting the face or extremities. This condition is associated with autoimmune and inflammatory processes, often linked to systemic diseases such as lupus erythematosus.

**Why the Correct Answer is Right**
The correct answer is associated with the autoimmune disease lupus erythematosus (LE), which is known to cause skin manifestations, including "en coup de sabre." This condition is thought to result from the deposition of immune complexes in the skin, leading to inflammation and scarring. The pathophysiology involves the activation of T cells and the production of autoantibodies against nuclear and cytoplasmic antigens.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while lupus erythematosus can cause various skin manifestations, "en coup de sabre" is not the most characteristic feature of this disease.
**Option B:** This option is incorrect because while psoriasis is a skin condition characterized by inflammation and scarring, it does not typically present with the unilateral atrophy and scarring seen in "en coup de sabre."
**Option C:** This option is incorrect because while dermatomyositis is an autoimmune disease that affects the skin and muscles, it is not typically associated with the characteristic skin lesions of "en coup de sabre."

**Clinical Pearl / High-Yield Fact**
Remember that "en coup de sabre" is a rare but distinctive skin manifestation of lupus erythematosus, characterized by unilateral atrophy and scarring of the skin.

**Correct Answer: D. Lupus erythematosus**