**Core Concept**
Behçet’s disease is a systemic vasculitis characterized by recurrent oral and genital ulcers, uveitis, skin lesions, and arthritis. It primarily affects medium and small vessels, leading to inflammation of mucous membranes and joints.

**Why the Correct Answer is Right**
Behçet’s disease presents with recurrent oral ulcers, genital ulcers, conjunctivitis, and arthritis—key features matching the patient’s symptoms. The presence of multiple mucocutaneous ulcers and joint pain, especially in a young adult, strongly suggests this diagnosis. The ulcers are typically painful, shallow, and recurrent, and are often symmetric. Unlike genital herpes (viral), it does not have a typical prodrome or vesicular phase. Polyarteritis nodosa involves systemic vasculitis but typically presents with nodular skin lesions, hypertension, and organ dysfunction, not mucosal ulcers. Gonorrhea causes urethral discharge and painful urination, not oral or genital ulcers without other classic signs.

**Why Each Wrong Option is Incorrect**
Option B: Genital herpes presents with painful, vesicular lesions, often preceded by prodromal symptoms, and is typically associated with fever and lymphadenopathy. The patient has no mention of vesicles or systemic infection, and oral ulcers in herpes are usually less recurrent and more localized.
Option C: Gonorrhea causes purulent discharge and dysuria, not recurrent mucosal ulcers or arthritis. It does not cause oral or genital ulcers as a primary feature.
Option D: Polyarteritis nodosa primarily affects medium-sized arteries, causing hypertension, renal failure, and skin nodules. It does not present with recurrent mucosal ulcers or conjunctivitis.

**Clinical Pearl / High-Yield Fact**
Remember: **"Oral ulcers + genital ulcers + arthritis + conjunctivitis = Behçet’s disease"**. This triad is highly specific and should prompt immediate consideration of Behçet’s in any young adult with recurrent mucosal ulcers.

✓ Correct Answer: A. Behyet disease