**Core Concept**
Dermatitis herpetiformis is a chronic skin condition characterized by intensely itchy, blistering skin lesions. It is a form of cutaneous manifestation of celiac disease, an autoimmune disorder triggered by gluten sensitivity.

**Why the Correct Answer is Right**
The drug of choice in dermatitis herpetiformis is dapsone, a sulfonamide antibiotic that has anti-inflammatory properties. Dapsone works by inhibiting the production of leukotrienes, which are chemical mediators involved in the inflammatory response. It also has a direct effect on neutrophil chemotaxis and activation, which helps to reduce the intensity of the skin lesions. Additionally, dapsone has been shown to reduce the levels of inflammatory cytokines, such as TNF-alpha, which play a role in the pathogenesis of dermatitis herpetiformis.

**Why Each Wrong Option is Incorrect**
**Option A:** Dapsone is the correct answer, not sulfasalazine, which is a different anti-inflammatory medication used in the treatment of conditions such as ulcerative colitis and rheumatoid arthritis.

**Option B:** Topical corticosteroids may be used to reduce inflammation and itching in dermatitis herpetiformis, but they are not the primary treatment. Dapsone is more effective in reducing the severity of the skin lesions.

**Option C:** Oral corticosteroids may be used in severe cases of dermatitis herpetiformis, but they are not the first line of treatment. Dapsone is generally preferred due to its efficacy and safety profile.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the treatment of dermatitis herpetiformis involves not only the use of dapsone but also a strict gluten-free diet. Patients with dermatitis herpetiformis should be advised to follow a gluten-free diet to prevent relapses and to manage symptoms effectively.

**Correct Answer:** D. Dapsone