A 35-year-old woman from rural India presents with recurrent oral ulcers, genital ulcers, and painful nodules on her shins. Ophthalmologic examination reveals anterior uveitis. Which is the most common cause of vasculitis in this clinical presentation?

Explanation

## Behçet's Disease: Diagnosis and Vasculitic Features **Key Point:** Behçet's disease is a chronic, relapsing vasculitis characterized by the classic triad of oral ulcers, genital ulcers, and ocular involvement (uveitis). It is the most common cause of vasculitis presenting with this constellation of findings. ### Diagnostic Criteria (International Study Group) For diagnosis, **recurrent oral ulcers** (mandatory) PLUS 2 of the following: 1. Recurrent genital ulcers 2. Ocular lesions (typically anterior uveitis) 3. Skin lesions (erythema nodosum, pseudofolliculitis, papulopustules) 4. Positive pathergy test ### Epidemiology & Geography - **Most common** along the "Silk Road" (Mediterranean, Middle East, East Asia) - Prevalence: Turkey ~600/100,000; Japan ~10–15/100,000; India ~0.5–1/100,000 - Female predominance in ocular disease; male predominance in systemic/vascular disease - Peak onset: 20–40 years ### Vasculitic Pattern | Feature | Behçet's | PAN | Takayasu | GPA | |---------|----------|-----|----------|-----| | Oral ulcers | **Yes (100%)** | No | No | Rare | | Genital ulcers | **Yes (75%)** | No | No | No | | Anterior uveitis | **Yes (70%)** | No | No | Rare | | Pathergy test | **Positive (60–70%)** | Negative | Negative | Negative | | Vessel size | Small & medium | Medium & large | Large | Small & medium | | ANCA | Negative | Negative | Negative | **Positive** | | ESR/CRP | Mild elevation | High | High | High | **High-Yield:** The **pathergy test** (intradermal needle prick → papule/pustule at 24–48 h) is highly specific for Behçet's and supports the diagnosis when positive, especially in endemic regions. **Clinical Pearl:** Ocular involvement in Behçet's (posterior uveitis with retinal vasculitis) is the leading cause of blindness in young adults in endemic areas and requires aggressive immunosuppression. **Mnemonic:** **MOUTH** — **M**ucous ulcers (oral), **O**cular involvement, **U**lcers (genital), **T**hrombosis, **H**ypopyon [cite:Park 26e Ch 24] [cite:Harrison 21e Ch 319]